Roll trigger

[hotbrass]

Can someone describe the process to make a smooth long roll trigger?

I have never made a roll trigger and would like to try.

The infomation I have found mostly describes what a roll trigger is, not how to make one. Though I am sure I can do it on my own, I would like to hear how some of you make a roll trigger.

Thanks!

[Greg Derr]

I make "roll triggers" by using extra long hammer hooks and slightly rounding over the sear nose, which tends to "roll" off the hammer hooks. Hammer hooks should be .240 tall. Greg

[1911Tuner]

Hammer hooks should be .240 tall. Greg

Forsooth! Them's some long hammer hooks, there Greg!

:D

Just goofin' on ya. I know it's a typo. Incidentally, I agree...but I like'em .025 inch.
I know. Flip a coin for the .001 difference.

[Lazarus]

Well, if you can define what a roll trigger (a.k.a. rolling trigger break) actually is, you have a much better chance of finding one. There are lots of terms that are really someone's subjective attempt to describe how something feels. Not too specific, just yet huh? A good place to start is the trigger pull on your personal blaster - assuming that you did the trigger job. What kind of trigger pull do you have now?

My 2 cents worth on rolling breaks is this: most people would not know the difference between a horse and a rolling trigger to begin with. However the 1911 design is pretty much associated with a "straight" or crisp trigger because the trigger itself bears directly upon the sear.

Now take a CZ pistol for example. This system uses a leveraged trigger system and is ideally suited to having a rolling break, simply because the sear is moving more slowly than the trigger, and it is thus under mechanical leverage. I say stick with the design. 1911 design suggests a straight trigger pull. I'd say safety is the primary consideraton, not the subtleties of someone's imagination. What could be fairer than that?

-Lazarus

[Greg Derr]

Roll triggers are used by a small portion of " Bullseye" community. Brian Zins who's won Perry a bunch advocates using it, as he does. To get those long hooks is tricky. Some folks like a looong roll, other a short roll. As Laz said many will not know the difference. Greg

[hotbrass]

Thanks Gregg. I have built several BE guns for myself and I wanted to try a roll tigger. I have a couple of virgin hammers laying around and I guess I will smooth out the hooks and break the edge on the sear to a large radius, unless someone else has a better plan.

[Jerry Keefer]

There are in fact two different fulcrum points in the 1911 trigger system. As Gregg states, roll triggers are common place within the Bullseye game, and top level shooters will quickly test one's ability to produce quaility trigger work. Just ask any AMU or Marine Corp armorer. 1911 triggers are a specialized skill.

Jerry

[hotbrass]

Thanks for the input Jerry.

I have done so many 1911 trigger/sear/hammer/disconnector jobs, I cant begin to count. But never done a roll trigger before. So in light of all the discussion, and no response to my question, I guess I will just jump in and get my own experience and develop my own method.

I am still not sure where I could find a hammer with quarter inch hooks.

[robot1911]

Just a note: Try to find a sear with a large crown area. IMHO the hooks aren't as important in a roll trigger as is the sear. The hooks (I also like .025 for a roll) will be sliding across the sear crown and the more crown there is to work with, the better your chance of getting a good roll.
There's another way to get a roll trigger, BTW. You can use long hooks but shape the sear crown to a half-round. This configuration will have the sear sliding from under the hooks...which will need to be mirror-polished on the underside.

Bob

[Jerry Keefer]

Hot Brass

One of Brian Zinns' armorers, Mark Webster, wrote a very good thread about a year ago on Brian's forum describing the procedure and difficulty in achieveing protection. You might try to pull that up. There's some discussion on his site now about roll triggers, but I think Mark wrote exactly what you are looking for..

Jerry

[hotbrass]

Thanks guys! Now that is what I am looking for.

[Jammer Six]

My 2 cents worth on rolling breaks is this: most people would not know the difference between a horse and a rolling trigger to begin with.
What's a horse?

[Canuck-IL]

The post re roll triggers on the Zins forum is gone - looks like most of the site has been flushed of discussion. There's a thread on the Enos forum that discusses it...
http://www.brianenos.com/forums/index.php?showtopic=34182&hl=roll+trigger

You have to look down the thread a bit as the first several are just the ramblings of the naysayers.
/Bryan

[Lazarus]

Thanks guys! Now that is what I am looking for.

Personally, I don't think so.

I still don't think anyone has taken a stab at describing what a roll trigger really is. So, unless we have a definition, we won't know if we have one....

Now, safety is primary as it should be with any trigger work. That means that the hammer will stay statically cocked and will not fall if the gun is bumped. That also means that in the statically cocked position, the engagement is positive. That's a technical term, by the way...positive.

But what happens when the trigger is being pulled? That is, the sear is moving, but the hammer has not been released. We do not want the trigger to stage. In other words we don't want it to halt mid-way along the hammer hooks while we reconsider the meaning of life and the validity of our sight picture. On the other hand, we want some "feel" to the trigger pull, not just a sudden and abrupt hammer fall, without any percieved movement in the trigger.

So, what is it that we are trying for...? Some might call the rolling break just another term for trigger creep. And they would be correct, mostly. But creep is usually a coarse and unpredictable jerking movement as the trigger is being pulled. Nonetheless, there is still a perceived movement between hammer and sear during the trigger pull...but it must be made smooth. There is more to the story. Anyone care to elaborate?

-Lazarus

[hotbrass]

You go ahead and talk it up Lazarus. I will check with Paul Harvey for the rest of the story.

In the mean time I will be building the undefined roll tiggers for a couple of 1911's.

Thanks everyone.

[Jammer Six]

I hate horses. And they hate me right back. So I'm staying away from roll triggers.

I never met a horse I couldn't fall off- has something to do with my eyes swelling shut.

I can fall off a MERRY-GO-ROUND!

[niemi24s]

Hi Lazarus: Nice thought-provoking post. Got me wondering.

1. Does positive engagement mean the sear nose raises the hammer hooks slightly as the trigger is pulled?

2. From this thread, I get the idea a "roll trigger" has sear nose and hammer hooks shaped as matching arcs of a circle, with the circle center at the sear pin center. The sear can then "roll" (rotate) out from under the hooks without either raising them or allowing them to lower (until disengagement occurs). Is this what a roll trigger is?

3. If my description in 2., above, is OK (I'd like to call it "neutral engagement") the mid-spec USGI trigger job depicted in the Sear Nose/Hammer Hook Angle thread must show negative engagement - as the hammer will fall slightly as the trigger is pulled. Does that make sense?

Was anticipating some good discussions as a result of your post and wanted to make sure I had a correct understanding of the basics. Cheers.

P.S.: Maybe this diagram will help. It shows the three engagements as I understand them and each is drawn with exaggerated sear noses & hammer hooks just for clarity. The little curved arrows pointing down to the left show the arc of travel of the sear nose surface farthest from the sear pin.

http://i129.photobucket.com/albums/p232/niemi24s/P8030001d.jpg

The one on the right is the U.S.G.I. set-up after the hook tips are dressed to obtain the required trigger pull (as stated on the blueprint). This would have to (I think) eliminate the hook tips protruding beyond the forward edge of the sear nose and change the positive engagement to a negative engagement.

[Lazarus]

Niemi, glad you found my comments interesting. I thought maybe I was dense and that every technical point had already been fully explained. A few reality checks later confirms that there is still a lot more to go, since nobody so far has really described what they mean by rolling.

Thanks for your diagrams. It is a bit misleading to consider the hammer hooks only. Hammer hooks is a big subject in itself. I'd like you to first consider the relationship between the hammer hooks and the sear face when the hammer is statically cocked - no movement has taken place. The relationship is quite complex, and I hope our physics gurus can help us along. The fundamental static relationship can be approximated using inclined planes. The external forces can be simplified in this case (I believe) to a single force (hammer spring) acting along the line that is tangent to the circle that is drawn from the hammer pin (center) to the tip of the hook's vertical face. For now we can ignore the effect of the sear spring.

In a positive engagement, the engagement is forced more tightly together by the external (hammer spring) force. This result is due to the analysis of the inclined planes represented by the hammer hooks and the sear face. In a neutral engagement, there is no net engagement or disengagement resultant. And in a negative egagement we have a net force working towards disengagement. It is true that negative engagements can remain statically cocked, if the disengagement force is lower than the static friction (stiction) between the two parts. Bumping the firearm can change this relationship very quickly.

So as a humble beginning, lets look at the statically cocked engagement and then progress slowly toward disengagement and the different ways that it can take place. Besides, my fingers get tired easily.

-Lazarus

[gbw]

Nice thread.

So, which one will give a 'glass rod' break - no creep, no roll, no nothing. Because I often hear this claim. It looks like the negative is the only candidate, both of the others must creep, however smoothly. But that negative geometry (trigonometry) looks distinctly unstable - read unsafe - to me.

[hotbrass]

Ignoring everything else for the purpose of brevity, less hammer/sear engagement will give you a crisp trigger. Generally accomplished by reducing the area of the hammer hooks.

I will let the others elaborate.

[niemi24s]

Hi HotBrass: Does the center drawing depict what you presently understand a roll trigger to be?

Hi GBW: That negative engagement (if that's really the proper term) looks a bit scary to me too, but it is JMB's design - at least as reflected in the blueprints.

Hi Lazarus: What say we begin with a mid-spec USGI sear & hammer with the hooks shortened to, say, 0.025 inch (to eliminate the tips hanging over the front edge of the sear nose), the hook angle unmodified at 86 degrees and an unmodified sear nose?

Let me know and I'll churn up some sort of sketch.

[gbw]

How do you accurately measure the angle of the hammer hooks? Is it necessary to measure it? It seems either it would be a benefit to measure it, or to be able to cut them to a specific angle.

[niemi24s]

Hi GBW: Only ways I can think of to measure the hook angle would be either with an optical comparator (big multi-thousand $ instruments) or a pocket comparator with a protractor reticle. Most pocket models, however, lack sufficient magnification. My 60X shop microscope has barely enough magnification for the job, but doesn't have a protractor reticle.

But, as you suspect, it's probably not too important to know whether the hook are at, say, 87.5 degrees but whether they're about 90, more than 90 or less than 90 degrees. This can be eyeballed with suitable magnification. My 60X 'scope is OK for this.

I've read that cutting hooks to 90 degrees is possible with India & Arkansas stones which have good sharp 90 degree corners - verified with a good square. Not sure how get them to any other angle, other than finding a stone with a corner at the angle you want or having a stone dressed to that angle.

How they do the flats & hooks at the hammer factory? Hm-m-m-m....

[Canuck-IL]

On a mill...?
/B

[Lazarus]

Looks like some thoughts are beginning to emerge now, and that's a good sign. I went back to my earlier post today to clarify the force vector exerted by the cocked hammer, btw.

Before we get sidetracked, I'll just mention that it is of little consequence what the included angle of the hammer hooks happens to be. ***GASP*** I hear it already! Blasphemy! Yes, it can be measured by standard machine shop practices and it can obviously be mill cut so the included angle is 90 degrees. So what! There is a huge thread on THR on cutting hammer hooks so they are exactly 90 degrees. This is all hot air. This method MAY work for some smiths using a certain type of hammer and sear and who want something repeatable that does not require thinking. But for the moment, we are going to require thinking, because, well, it is more interesting than watching TV.

It is the relationship between the hammer and the sear that we must take into account for this discussion. The included angle of the hammer hooks by itself doesn't give us anything to work with. The relationship between the vertical hammer hook face and the size, shape and relative angle of the sear nose is required. But there is even more.

Keeping things simple to start with is a great idea. Niemi suggested a hook height of .025 and that is good. Let's also start with a sear face parallel to the vertical hammer hook, without any secondary or relief cut. Finally, let's refer to the original hammer drawing and look at how the hooks are positioned vs the hammer pin. Specifically, extend a line from the hammer vertical face down through the hammer and note where it falls. I hope Niemi has a hammer drawing handy for reference. Then we can make some guesses as to what is positive and what is negative.

-Lazarus

[gbw]

Before we get sidetracked, I'll just mention that it is of little consequence what the included angle of the hammer hooks happens to be. ***GASP*** I hear it already! Blasphemy! Yes, it can be measured by standard machine shop practices and it can obviously be mill cut so the included angle is 90 degrees. So what! There is a huge thread on THR on cutting hammer hooks so they are exactly 90 degrees. This is all hot air. This method MAY work for some smiths using a certain type of hammer and sear and who want something repeatable that does not require thinking. But for the moment, we are going to require thinking, because, well, it is more interesting than watching TV.

It is the relationship between the hammer and the sear that we must take into account for this discussion. The included angle of the hammer hooks by itself doesn't give us anything to work with. The relationship between the vertical hammer hook face and the size, shape and relative angle of the sear nose is required. But there is even more.


-Lazarus

I don' think I can buy this. Maybe I'm wrong, but I think the hook angle, alone, has to matter. Severe examples: With a parallel sear face, if the hook angle is 20 degrees it will be nearly impossible to pull the trigger. If it is 140 degrees it will be impossible to keep the pistol cocked. So it surely matters. Now where it begins to matter, and by how much, are important questions. 1 degree, 3, 5? What gives the type, weight, consistency for which one is looking. And it also has to last awhile, and absolutely resist unintended release.

And just so's it don't get too simple, spring rates and hammer /sear materials and hardness matter too.

[David Rose]

It appears to me, that you guys are disregarding the hammer hook angle. In a previous thread, we spoke of whether that angle aligned with the center of the hammer pin hole or not. What Niemi has drawn is a positive "point" on the sear, not the hammer hook. Niemi's drawing will drag the sear farther along the hammer hook with the "positive" drawing. But positive engagement, in my definition, would cam the hammer back slightly. That would depend on the hammer hook angle... I'm not talking about the "included angle" on the hammer itself, but the face of the hooks to the pivot pin of the hammer.

I'm still not sure what a "rolling trigger" is. But with Niemi's positive pic, the face of the hammer hooks would determine the smoothness, with length of pull determined by hook depth. With the negative pic, the face of the sear contact vs the very tip of the sear contact would determine smoothness, with the length of the sear face determining length of pull.

David

[Lazarus]

Ok GBW, I think it is a good thing to be sceptical. I'm going to suggest that at the moment you are making assumptions that have no basis as yet. Many smiths also make these assumptions when they start doing the trigger job, and they might even be correct - sometimes.

Think of a hammer all by itself for a moment. Someone has cut a shelf on the hammer. How did that guy know where to put the shelf? Then a 90 degree angle is formed to the shelf, making a set of hooks. Great, now there is a lonely set of hammer hooks at some unknown relationship to the hammer's center of rotation. But, they are square! Ok, big deal! I'm just saying that for the purposes of entertaining and amusing discourse that we hold off on our assumptions about correctness or incorrectness while we ask some questions. And my first question is what do the original hammer drawings show?

Jumping back to Niemi's earlier post, we will make the following statements about engagements. Note that these statements are practical and empirical rather than being technical descriptions of why stuff is the way it is.

Engagement Basics:

Positive Engagement: The hammer will move backward by some amount before falling. This is considered a "safe" engagement.

Neutral Engagement: The hammer remains stationary during trigger pull, then falls. A neutral engagement is "safe" but should be regarded as potentially dangerous. More on that later.

Negative Engagement: The hammer will creep forward by some amount before falling. This engagement is "unsafe" since it relies solely on friction to keep the hammer cocked.

A further note on the above is as follows. It is often difficult to tell what kind of engagement you are working with while the gun is fully assembled. Sometimes the hammer movement just before hammer drop is extremely small. I have found that working with the springs removed is a much easier way to evaluate what is happening.

-Lazarus

[niemi24s]

Maybe the best first sketch should be of the mid-spec parts per the U.S. Army blueprints as initally assembled (without any fitting) including the hammer & sear pins. May as well start from "square one", huh?

Lazarus doesn't think the hooks' included angle matters much and he's probably correct because he's (I think) referring to the angle formed at the intersection of the hooks and the adjacent flat areas. The angle others refer to is either the angle between the hooks & sear nose, the angle between the hooks & the line from the hooks to the hammer pin center, or some other angle.

We need a common visual frame of reference. Otherwise Poster X is going to think Poster Y's dumber'n a mud brick - cuz they're talking about two different things! Take me a few days to get one posted - cut my trigger & drawing finger pretty bad yesterday. Regards

[Iron bottom]

Going from positive to neutral or negative? Rolling like a fifty dollar boat maybe. A little less pressure on the trigger just before sear and hammer disengagment. I believe this could be accomplished by modifying the hammer hooks or the sear or both.... "break corner to obtain required trigger pull"..... I like positive for safety reasons and want no part of any negative going hammer. As NIEMI pointed out, the glass to do a precision job would cost big bucks, and is probably pretty rare in gun shops.

[Lazarus]

Hello Iron, you are getting a little ahead of us, but you bring up some important points. First, a strong magnifier is a real necessity for working on engagements. And, yes, the complete description of a full trigger pull gets complex really quickly. Frankly, I'm not sure that I can specify with complete certainty what is happening once the trigger starts moving.

Having said that, I have some mental contructs that are helpful to me to follow. Naturally our first priority will be safety. And, if that term needs further clarification let's say this:

Safe
An engagement is "safe" if the spring forces work to keep the hammer and sear engaged. We refer to the condition of a fully cocked hammer, in its static condition. In other words, no outside forces are at work.

Later, if interesting to the group, we can talk about whether an engagement remains "safe" during the actual trigger pull. In other words (as Iron Bottom has pointed out) as parts begin to move, their relative positions change, and so may our description of positive, negative and neutral.

-Lazarus

[robot1911]

"We need a common visual frame of reference. Otherwise Poster X is going to think Poster Y's dumber'n a mud brick - cuz they're talking about two different things! Take me a few days to get one posted - cut my trigger & drawing finger pretty bad yesterday. Regards
Lazarus"

I don't know about you guys, but I've never known any shop with the kind of 'glass' that's being discussed here. This discussion is really interesting reading, but from a practical viewpoint, here's what I do when I'm not sure about my hammer/sear engagement, or if I'm seeking a particular relationship: I put the assembled pistol in my vice and setup a dial indicator on the tip of the hammer. It never fails to tell me whether I have +/- or 0. And I sure agree with some of you in that I do not like a negative engagement trigger job. To the best of my knowledge, one has never left my shop since I started doing triggers in 1950. I've always squared the hooks to 90*, set the hook height to either .018 or .020 for NRA match pistols (.025 for duty), and put a slight polished radius on the hammer hooks' leading edge. Over the years I've tried many other combinations but always have returned to the above. Works for me!
BTW, Roll triggers are totally different.

Bob

[1911Tuner]

[quote=robot1911]I've tried many other combinations but always have returned to the above. Works for me!

Works for me too, Bob. ;)

[niemi24s]

These drawings are of an un-fitted mid-spec sear & hammer installed in a mid-spec receiver. Dimensions are in inches (millimeters), rounded to the nearest 0.001 inch. Those with an asterisk (*) are blueprint specs, others were calculated from these.

The first is the whole picture. The angle between the broken (dashed) SL line and the sear's nose is 90 degrees.

http://i129.photobucket.com/albums/p232/niemi24s/P8040001d.jpg

These second is a close-up view of just the hooks & sear nose, showing the 0.002 inch hook "overhang" before fitting and the maximum allowable 0.005 inch radius at the junction of the hooks & flats.

http://i129.photobucket.com/albums/p232/niemi24s/P8040002d.jpg

Except for the "break corner to obtain required trigger pull", referring to the hook tips in the blueprint, this is my composite view of JMB's design as reflected in those blueprints. Don't know how much that corner was "broken", but have a strong hunch it was enough to eliminate the 0.002 inch overhang - but I've been wrong before.

If anyone spots something that's incorrect or just doesn't look right please inform me.

BTW, even though the bench model optical comparitors are big bucks, I got the 60X shop microscope for about $70 on EBay. While it has no protractor reticle, the reticle it does have can measure up to 0.100 inch with graduations of 0.001 inch. Got it for measuring indentation diameters for my Brinell hardness tester. Regards

P.S.: I guess hook angle could be measured (if you really had to or wanted to measure it) with a set of angle gauges (like Starrett's #466, about $100), but I'm pretty sure some high-power magnification would still be needed just to see the fit. Then there's the inevitable radius at the hook/flat junction to contend with! Methinks a magnified eyeball estimate is probably all that's really needed.

[Jammer Six]

I have two questions:

what is the "included angle", and how do you make hooks DEEPER? That is, I've purchased several sets that came at about .020. How would you make them into .025?

[niemi24s]

Hi Jammer Six: In geometry, say of triangles, the angle between (formed by) two sides is called the included angle (between those two sides). The other two angles are the non-included angles (between those same two sides) - which are included between other pairs of sides. Ghastly stuff, huh?

The 0.030 inch hammer hook dimension is the mid-spec U.S.G.I. blueprint value - before any fitting. Many manufacturers offer "prepped" hammers with hooks ranging from 0.019 inch (Les Baer) to 0.022 inch (Ed Brown) according to the Brownells catalog. Maybe that's what you have - prepped hammers.

Deepening their hooks from 0.020 to 0.025 inch would involve, I think, carefully filing & stoning off 0.005 inch of the upper part of the adjacent flats without undercutting the hooks. Notice the "I think", because I've never intentionally done it. Maybe try to find someone with stock USGI hammers and make a trade - then dress them down to 0.025 inch. Are you sure the 0.020 hook hammers won't work for you?

.

[Lazarus]

Niemi, thanks for your drawings. I might just need more coffee this morning, but they are not making sense to me at the moment. Looks like I may have to break out my drawing stuff and find a scanner!

My first area of interest at the moment is a hammer drawing. Relationship to the receiver unimportant. Specifically, I'd like to see the hammer's shape, hammer pin hole and how the location of the hammer hooks is derived relative to the hammer pin.

Here is where I'm going with this thought. I think it will be obvious once we have a simplified sketch of the hammer and sear that there is a triangle of forces at work. This concept can be applied generally to most types of firearms engagements. The same principle is used in structural design with the use of a truss. The triangular shape is the strongest structural shape, next to an equally sized solid, that we know. From geometry, we also know that a triangle will not change shape as long as the points remain intact. Well, one of the points of the structural triangle will correspond to the hammer/sear engagement. The other two points will be the hammer pin and the sear pin. For those of you who are M.E.'s, neither the hammer nor the sear "points" need to be moment resisting joints - that is, they can rotate without affecting the integrity of the triangle.

But, the only time there will be rotation in the hammer and sear points is of course if the engagement point is broken (trigger pulled). In the 1911 the trigger/disconnector apply rotational force to the sear-engagement leg of the triangle. At some point, the engagement is broken, as is the triangle of forces (hammer and sear free to rotate).

As an interesting comparison, the Jewell trigger uses an articulated leg for the sear to hammer side of the triangle. This type of trigger does not depend upon the traditional sear face/hammer hook relationship. Instead, one leg of the triangle is forced to "buckle", which then breaks the engagement point of the triangle as well. But, I digress.

Apologies for my lack of CAD drawing ability - I will try to get something together. For the time being, I wanted to approximate the direction of force exerted on the sear face by the hammer hooks, as well as the relative angles of the two parts. Since the parts are pinned, their movement is rotational, not linear. Hammer/sear relative movement can only be approximately linear if the actual amount of metal in contact is very tiny. We may want to consider the engagement as a point for some discussions, but I think it is understood that with any reasonably safe engagement, relative movement is rotational. I think this will help to develop some more realistic mental constructs on what we are trying to achieve with our stones, jigs, vertical mills, and toothpaste!

-Lazarus

[niemi24s]

In the upper drawing, the force exerted on the sear nose by the hammer hooks is perpendicular to the broken HTR [for Hook Tip Radius}line, or the same as its left hand dimensioning line (touched by the <--- arrow).

It's about 83 degrees to the sear nose surface.

The hammer pin hole's the larger circle on the right, the other circle is the sear pin hole.

P.S.: This drawing replaces the top drawing in Post #34 and hopefully makes it a little easier to see what's what. Remember - these are unfitted mid-spec USGI parts, as they would be pinned in the receiver and placed in the fully cocked position.

http://i129.photobucket.com/albums/p232/niemi24s/P8050001d.jpg

No modifications were made to the second drawing in Post #34 and it is not included here to save space.

The first two fitting actions, as I understand, are usually shortening the hooks to maybe 0.025 inch and dressing the hook/flat angle from 86 to 90 degrees. If so, I'll churn up a close-up drawing of this and see whether we have + or - engagement. If something else is usually done first, please let me know - especially if 0.025 inch hooks are too short to make a "roll trigger" (whatever that is).

[Lazarus]

Yup, the felt marker really helped! This is an excellent drawing. I'm just in the habit of seeing it and drawing it the other way around. Now just let me get my thoughts together so we can talk about this drawing. It is marked "Before any fitting". However this relationship is very close to the way the engagements are currently being cut by Colt on current production Series 70's.

So, while this engagement drawing - if duplicated on real parts - may not yield the most buttery, crisp-breaking trigger. It will be nonetheless be safe and plenty good for Government work (pun intended). But as I said, let me get some thoughts together first. My birds are screaming their brains out at the moment and its hard to think!

-Lazarus

[niemi24s]

While Lazarus is calming his flock, here's the drawing mentioned (threatened?) in Post #38. It's a modification of the close-up of the original un-fitted parted showing the results of shortening the hooks to 0.025 inch and cutting them to 90 degrees to the adjacent flats.

http://i129.photobucket.com/albums/p232/niemi24s/P8060001d.jpg

Because the hammer hooks will fall about 0.001 inch during disengagement (down to the broken red arrow), this engagement is technically, I guess, negative - although not by much.

If all that was done to USGI 1911's was to dress the hook tips "to obtain the required trigger pull", the amount of negative engagement would be the same even with 86 degree hooks.

Neutral engagement will be obtained if the sear nose is dressed down to meet the broken red arrow. Doing so will keep the hook tips from either rising or falling at any time during during disengagement.

Positive engagement will be obtained if the sear nose is dressed down below the broken red arrow at the front (left) of the sear while leaving the rear (right) of the sear at the original length (from the sear pin). Doing so will cause the hook tips to rise and the hammer to cock more during disengagement.

All this stuff prompts some questions:

1. If negative engagement is a bad thing, how come the design calls for a little bit of it? Did USGI factory fitters stone down sears to eliminate it? Or, why weren't sears noses made with an 85 or 86 degree aft corner to provide a little positive engagement with sears hot off the sear making machine?

2. Note there's no breakaway/relief angle cut at the rear (right) edge of the sear nose yet. Is this about the stage where the process of making a roll trigger begins? Do roll triggers have breakaway/relief angles?

3. What's the "point of departure" for the other types of triggers, like carry, bullseye, roll, way-too-light race, etc?

[Jammer Six]

Where did these drawings come from?

How were the measurements taken?

Good thread!

[niemi24s]

These drawings were done on my "drafting table" with rule (1/100 inch graduations), pen, pencil, etc. Scales of the the originals were either 10:1 or 200:1.

There are no measurements, per se, in these drawings. The dimensions in these drawings are either the U.S. Army's blueprint specifications (available in the Technical Issues section of this forum) or calculations based on them. No real-world gun part was measured to obtain any of these dimensions.

[gbw]

[QUOTE=robot1911 .... but from a practical viewpoint, here's what I do when I'm not sure about my hammer/sear engagement, or if I'm seeking a particular relationship: I put the assembled pistol in my vice and setup a dial indicator on the tip of the hammer. It never fails to tell me whether I have +/- or 0. And I sure agree with some of you in that I do not like a negative engagement trigger job. To the best of my knowledge, one has never left my shop since I started doing triggers in 1950. I've always squared the hooks to 90*, set the hook height to either .018 or .020 for NRA match pistols (.025 for duty), and put a slight polished radius on the hammer hooks' leading edge. Over the years I've tried many other combinations but always have returned to the above. Works for me!
BTW, Roll triggers are totally different.

Bob[/QUOTE]

I believe Old Master 1911Robot nailed this one. All of the possible combinations and permutations in geometry are technically interesting, it's true, but they (and their effects) are nearly endless - as are the possibilities for speculation. But at the end of it all, a positive engagement makes me happiest. I do have a couple of questions left:

On match-only pistols, what engagement-type is preferred?

"Roll triggers are totally different" - a quick definition of how?

On positive engagement setups, should it be positive enough to make the hammer/sear re-set themselves to full engagement depth if trigger pressure is released before letoff?

And a biggie - why did the original specify a slight negative? This answer may never be known, I suppose, but I sho' does wonder.

[Lazarus]

http://i129.photobucket.com/albums/p232/niemi24s/P8060001d.jpg


Niemi, I believe you were correct when you said that the drawing above would be negative. I have not personally experimented with parts that are cut like the above, but it makes sense that the tip of the sear nose must be placed within the hammer vertical face. Otherwise you have the tip of the hammer working on an inclined plane (sear nose) and it is clear that the sear would be pushed out of engagement. Practically speaking, I've never seen a sear nose large enough to extend beyond a .025 hammer hook, but that's beside the point.

What I'd like to do is modify the drawing (above) to show a sear nose that fits comfortably inside the hammer hook by at least .005", but keeping the other relationships the same. Then, please add an arc to the drawing that is swung from the sear's center with a radius that is the same as the sear tip. The relationship between the hammer's vertical face and the arc is what we want to consider at the moment.


All this stuff prompts some questions:
1. If negative engagement is a bad thing, how come the design calls for a little bit of it? Did USGI factory fitters stone down sears to eliminate it? Or, why weren't sears noses made with an 85 or 86 degree aft corner to provide a little positive engagement with sears hot off the sear making machine?


I can't say from personal experience, but I doubt if 1911's were intentionally delivered with a negative engagement. I remember reading several accounts noting that the trigger pull was in the area of 7-9 pounds. That kind of pull weight results when the trigger is used to compress the mainspring. And that activity (compressing the mainspring) is an indication of a positive engagement.

What I can say is this: current production Series 70's come from the box with an engagement that is very close to your drawing, except for the detail that the sear tip lies inside the hammer hook rather than outside. These triggers weigh in at about 5-1/2 to 6-1/2 pounds.


2. Note there's no breakaway/relief angle cut at the rear (right) edge of the sear nose yet. Is this about the stage where the process of making a roll trigger begins? Do roll triggers have breakaway/relief angles?


Ok, let's look at it this way. With sear nose contact at least .005" inside the hammer tip, the sear is for the sake of discussion bearing on a single point. The other point of the sear is lying on the hammer flat. The function of this other point is simply to act as a limiter. In other words, the non-bearing point of the sear limits how far into engagement the sear nose will go.

Now, refer to the ammended drawing showing the arc of sear tip movement. As you can see, as soon as the sear tip escapes outside of the hammer's tip, you do, essentially, have a "breakaway" cut if you consider the new relative angles.

As to the question about whether roll triggers have breakaway cuts...well, I'll reserve judgement on this point. I think there is some basic misunderstanding about what the sear secondary angle or "relief cut" actually does. I would be inclined to focus on the mechanics of sear and hammer movement as the trigger is being pulled. An energy diagram is probably necessary to identify the different types of trigger pull. I don't think the average person could make a determination based solely on a blueprint.


3. What's the "point of departure" for the other types of triggers, like carry, bullseye, roll, way-too-light race, etc?

We've chosen to consider only triggers that are "safe". In other words the springs force the hammer and sear more closely into engagement. But within this definition you have a huge selection of possible trigger pull weights. Add to the idea of pull weight some concepts about what the trigger "feels like" as it is being pulled and you have even more possibilities. A description such as "way too light" can easily refer to a "safe" trigger by our definition of safe. Whether you can actually manage an 8 oz. trigger pull in real life is another question and another topic.

I do hope this subject is not becoming a huge snore. I think its pretty interesting myself, and I'm learning a lot by trying to describe some of the variables to consider when working on a trigger engagement.

-Lazarus

[hotbrass]

Esoterica at its finest.

Actually the trigger is right when the shooter declares it so. Angles, cuts, geometric drawings and discussion play no part in the making of a trigger pull, but the pictures are pretty. Its like a mathematician trying to figure out how to recreate La Gioconda, the painting or the opera, take your pick. It is 99.99999% art and a bare hint of science. A process based on experience, or for experience.

Yes, I read every post.

Carry on!

[Iron bottom]

Were the original hammer hooks square? I was under the impression they were a few degrees under square.

[niemi24s]

Hi Iron Bottom: The original (USGI) untinkered-with hooks are at 86 degrees to the adjacent flat areas and provide slightly negative engagement. Dressing them to 90 degrees makes no change in the amount of negative engagement - strange as it seems!

With either 86 or 90 degree flat hooks, the only way to eliminate the little bit of negative engagement is to dress the sear nose down to the line of the broken red arrow in the drawing. This'll give "neutral" engagement - neither negative or positive - and the hammer will neither rise nor fall during disengagement.

All this assumes the hook tips have been dressed down so they don't overhang the forward edge of the sear nose.

[niemi24s]

[QUOTE=Lazarus: "Practically speaking, I've never seen a sear nose large enough to extend beyond a .025 hammer hook, but that's beside the point."]

The spec for the width of the sear nose is 0.030 -0.003 inch, yielding a mid-spec value of 0.0285 inch. Mid-spec hammer hooks are 0.030 inch, so before any fitting is done on either, the hooks must protrude a wee bit beyond the forward edge of the sear nose - about 0.002 inch.

How about a little speculative esoterica? If the hammer hooks do extend forward beyond the sear's nose and:

1. the hooks are significantly harder than the sear, boosting the hammer and/ or continued use might cause the hooks to deform the sear's forward edge (radius it slightly) and smooth out the pull. But; if

2. the sear is significantly harder than the hooks, the same things would cause the sear to form an indentation /crease/groove/deformation (?) across the hook tips and cause a "jerk" in the pull. If so (and if this jerkiness is easily overcome) could this contribute to the feel of the "glass rod breaking" trigger?

If the later situation is descriptive, then (at least as I understand it) it must be avoided to get a "roll trigger". Avoided by either insuring the hooks don't extend beyond the sear or by dressing the forward edge of the sear nose so it cannot cause any deformation to the hook tips that will cause jerkiness.

While I work on the next drawing, ponder this: Can a roll trigger have positive engagement?

[Lazarus]

The spec for the width of the sear nose is 0.030 -0.003 inch, yielding a mid-spec value of 0.0285 inch. Mid-spec hammer hooks are 0.030 inch, so before any fitting is done on either, the hooks must protrude a wee bit beyond the forward edge of the sear nose - about 0.002 inch.


Yes, thanks for reminding me about the original drawings. Just because I have never seen a sear with a .030 nose doesn't mean much. These days it is hard to get a hammer that is much over .020".

That brings up an unrelated beef I have with manufacturing. Even though many of these aftermarket parts are very good quality (not as good as the original pre-1950's Colt parts) they tend to be EDM cut. That seems to be the most economical way to obtain fair precision and repeatability. But, a hammer hook cut with EDM looks like a mine field under a glass, and will feel rough and gritty if it is not smoothed out.

[BEGIN_RANT] A somewhat related rant on smoothing the hammer hooks. If you have a nice machine shop, the hammer can be mounted in the mill and smoothed up that way. Or, if you prefer doing it by hand the hammer can be smoothed up with a good quality stone. In either case, you will be using a tool that has a square corner. It is not impossible to have a milling cutter that is tapered 1/2 degree; nor is it impossible to imagine a rhomboid-shaped stone. But the overwhelming majority of shop tools employ 90 degree angles. Fine, no problem with a square corner. Cut the hammer square to its shelf. Just don't tell me you are performing this work according to a secret family tradition of making outstanding trigger pulls. Squaring the hooks, in my mind, is more correctly called smoothing the hooks. The fact that they come out square is irrelevant until we look at the particular sear that has been chosen to work with this particular hammer.

Granted, someone who always uses the same hammer, the same sear, in the same frame may have a shortcut method that he knows will work - that's great. I think many of the rest of us will be working on a new combination of parts every time, and that's why I'm pointing out the difference.[END_RANT]


How about a little speculative esoterica? If the hammer hooks do extend forward beyond the sear's nose and:

1. the hooks are significantly harder than the sear, boosting the hammer and/ or continued use might cause the hooks to deform the sear's forward edge (radius it slightly) and smooth out the pull. But; if

2. the sear is significantly harder than the hooks, the same things would cause the sear to form an indentation /crease/groove/deformation (?) across the hook tips and cause a "jerk" in the pull. If so (and if this jerkiness is easily overcome) could this contribute to the feel of the "glass rod breaking" trigger?

If the later situation is descriptive, then (at least as I understand it) it must be avoided to get a "roll trigger". Avoided by either insuring the hooks don't extend beyond the sear or by dressing the forward edge of the sear nose so it cannot cause any deformation to the hook tips that will cause jerkiness.


Niemi, you bring up another good point and that has to do with the quality of the materials (hammer and sear). I can't quote any specs on which part will do what. And I also think it would be very difficult to predict the outcome simply by working with the specs and the engagement drawings. All I can contribute on this subject comes from personal observation and guesses as to what might be happening.

One of those observations has to do with materials deformation. As you know, hardness is only one of the qualities that relate to a piece of metal. But whenever the yield point has been exceeded (expressed in pounds per square inch) there will be permanent deformation. That condition will cause your trigger of tomorrow to be different from your trigger of today.

I have noted that one or two of my custom guns' triggers getting increasingly lighter over a period of months. When I had a close look, I saw deformed sear noses and hammer hooks. The original engagements were on the order of .018" hammer hook, with .007" sear nose. Clearly the limits of the metal had been exceeded. So far, I have not noticed this process taking place when the hooks are .025" and the sear face is .015 to .020" with the same aftermarket parts as before.

I don't know exactly where the danger point falls, but a lot of info comes from keeping a watch on the condition of your sear nose. We do know that competition 1 or 2 pound triggers don't last long and have to be re-done every few months. The reason is simply that there is not enough metal in the engagement to handle the forces placed on it.


While I work on the next drawing, ponder this: Can a roll trigger have positive engagement?

Yes. Any type of trigger can be positive. We refer here to the statically cocked condition. Any trigger worth considering must be at least neutral and - more desirable - slightly positive. There is no safety problem with neutral, however you are placing your trigger at the very top of the energy curve where very small amounts of wear will cause big changes, usually pushing the trigger into negative territory.

The words roll trigger, clean breaking trigger, creepy trigger, etc. all refer to the shape of the energy diagram between the statically cocked condition and hammer fall. That's where we end up, if the point is to describe what happens when you start to pull the trigger.

-Lazarus

[niemi24s]

A little armchair 'smithing with pencil & paper did two things to the sear, as shown below:

http://i129.photobucket.com/albums/p232/niemi24s/P8081110d.jpg

1. The nose was dressed down so it forms the arc of a circle, centered on the sear pin. Because all points on the sear nose between A and B are the same distance from the sear's center of rotation, the sear will neither lift the hooks nor allow them to fall while the sear rotates during disengagement.

2. A slight relief/breakaway cut was made at the aft corner of the nose: to bring the forward edge of the nose directly under the hook tips; to reduce the length of the engagement angle; and to prevent any hook/flat junction radius (drawn as the maximum allowable 0.005 inch radius) from camming the sear forward during reset.

Based on what was found in a thread on another 1911 forum, this illustration depicts the essentials of a roll trigger - the hammer stays put during disengagement. This means sear engagement is neutral.

Can anybody see a way to get positive engagement with a roll trigger?

[Iron bottom]

Raising point B on the sear a tad? A tedious undertaking at the very least.

[Jammer Six]

Raising point B on the sear a tad? A tedious undertaking at the very least.
It's not hard at all.

You stone down A, and B comes up relative to A.

It's the first thing I did- I made the primary surface of the sear match the hooks under magnification. It created the worst trigger I've ever felt.

[niemi24s]

Hi Jammer Six: Thanks for the input.

When you dressed the sear nose for maximum contact area on the hooks, any recollection of whether you ended up with a positive engagement?

Did you happen to re-profile that sear's nose for minimum contact area in an effort to improve the trigger's feel?

If so, was this effort successful?

Hi Lazarus: I've a hunch you hit the nail squarely on the head with your comment about 90 versus 86 degree hooks. The shade tree gun plumber has just about got to use the flats as guiding surface for his hook-smoothing tools, and rhomboidal 86/94 degree corner stones would have to be custom dressed. Besides, I don't really see what practical difference this 4 degrees makes - but, somebody must have to arrive at the 86 degree specification.

And that somebody's no doubt a lot smarter than me - mebbe even JMB hisself!

[Jammer Six]

Hi Jammer Six: Thanks for the input.

When you dressed the sear nose for maximum contact area on the hooks, any recollection of whether you ended up with a positive engagement?

Did you happen to re-profile that sear's nose for minimum contact area in an effort to improve the trigger's feel?

If so, was this effort successful?
Yes, I cut secondary angle, and no, it wasn't successful by any standard.

I didn't have a way to measure, at the time, whether it was positive or negative. Now I can measure whether the hammer moves or not.

[gbw]

Niemi, they all look as though they could shift from neg. to positive during the release - as the sear moves throug it's arc. On these drawings, do you have enough room to swing arcs, centered on the sear pin, one touching the forward and one the aft sear corners (both relieved and standard)? I'd be curious to see if there is a change in aspect as the sear moves through its contact with the hammer notch.

I'm also wondering if stoning the sear such that only the aft sear corner ever contacts the hammer would be best.

(Beautiful work)

[niemi24s]

Hi GBW: Based on the consensus definition of positive, neutral and negative engagements, a depiction of an engagement shifting is in Post #40. The broken (dashed) blue hook profile that overhangs the sear nose is the original USGI and it has positive (will lift the hooks) engagement during the first 0.002 inch of travel. As the forward edge of the sear nose emerges from beneath the hooks, the engagement abruptly switches from positive to negative (allowing the hooks to fall until disengagement occurs).

The broken red arrows in both Posts 40 and 50 are arcs of circles centered on the sear pin and, as such, show sear nose profiles which will neither raise nor lower the hooks during disengagement (as long as the hooks don't overhang the forward edge of the sear nose) - providing neutral engagement.

Had to draw these arcs by sliding a French curve along between a series of calculated points on the arc because at a drawing scale of 200:1, the radius of the arc was over 80 inches on the paper!

P.S.: You have a good point about contact only at the aft part of the sear nose. Not sure now what it will or won't do - my little gray cells are (cell is?) all tuckered out at the moment. Cheers.

[Lazarus]

Actually the trigger is right when the shooter declares it so. Angles, cuts, geometric drawings and discussion play no part in the making of a trigger pull.

Hotbrass, this HAS to be the most curmudgeonly remark I've ever seen on a gunsmithing forum. Personally, I was hoping to learn something new from the comments and observations of others. While I do agree that a fine trigger - like fine wine and fine art - "just is", it is certain that an attitude like yours did not build the pyramids or the Grand Coulee Dam. :(

Niemi, thanks for the drawing in which you indicate an arc drawn from the sear center. I have been playing with this idea for some time now, but have not seen a properly dimensioned view of it until now.

There still seems to be some confusion about the terms positive, negative and neutral. So, I'll add a few more comments about the subject. Ignoring friction for the moment, a positive engagement will engage more firmly (sear and hammer are drawn together by mechanical forces). A negative engagement is opposite: mechanical forces push the sear away from the hammer and out of engagement. A neutral engagement is neither positive nor negative. There are no lateral force components, so the sear and hammer are neither drawn together, nor pushed apart. It is convenient to observe the hammer spur movement during the trigger pull. If the static engagement is positive, the hammer spur will move backwards before it falls. And v.v. for negative. With a perfectly neutral engagement, the hammer will not move at all before it falls.

Observing hammer spur movement is empirical. It is a convenient way to evaluate engagements, but it only tells part of the story. The critical thing to remember is that with a negative engagement, the hammer and sear are being forced apart by the mechanics of inclined planes. (There are lateral force vectors). The only way that a negative engagement can remain cocked is if there is enough friction between hammer and sear to counteract the lateral forces of disengagement.

I find that it is helpful to have a pin jig to evaluate hammer/sear engagements. A dangerous trigger can easily be found when there is no sear spring. A light push on the hammer will toss a negative sear out of engagement because the friction component is almost zero. I think this is one of the most helpful tests you can perform on any firearm without destroying or changing anything.

-Lazarus

[niemi24s]

This last (I promise) illustration depicts what may be the three basic forms of a roll trigger:

http://i129.photobucket.com/albums/p232/niemi24s/P8110003d.jpg

The key element in each of these is the broken red line because if a roll trigger doesn't cause the hammer to rise or fall during disengagement then sear/hook contact must be maintained along this red line all during disengagement.

Each shows: 0.025 inch hooks; about 0.020 inch of engagement; neutral engagement.

Fig 1, with square hooks and straight surfaces, might be the easiest to make. But, does it yield a good roll trigger? I don't know

Fig 2 may show Jammer Six's try at a roll trigger. If so, he reported it yielded the worst trigger he'd ever felt!

Figs 2 & 3, in addition to dressing the hooks to about 98 degrees, require dressing the hooks slightly concave (to the broken red line): methinks this (the concave part) would be extraordinarily difficult.

Fig 3 incorporates GBW's suggestion regarding aft edge contact. Would this yield a good roll trigger?

[Jammer Six]

Fig 2 may show Jammer Six's try at a roll trigger. If so, he reported it yielded the worst trigger he'd ever felt!
That's exactly right, that is what I did.

[hotbrass]

Hotbrass, this HAS to be the most curmudgeonly remark I've ever seen on a gunsmithing forum. Personally, I was hoping to learn something new from the comments and observations of others. While I do agree that a fine trigger - like fine wine and fine art - "just is", it is certain that an attitude like yours did not build the pyramids or the Grand Coulee Dam. :(



Oh dry up Laz.

My attitude is fine. I read every post, and it is certain with an attitude like yours the pyramids or the Grand Coulee Dam would never have been built. We would still be trying to figure out how sand is made. ;)

Carry on!

[niemi24s]

Hi Jammer Six: Thanx a bunch for confirming what I wrote. Your inputs have added welcomed substance to this somewhat theoretical discussion.

FWIW, the 0.020 inch long, "curved" engagement surfaces in Figs 2 & 3 depart from a straight line by a mere 0.00012 inch! Not sure I'd even be able to see that with my little 60X shop 'scope. Cheers

[Jammer Six]

You can see it by the "I see light at the back" or "I don't see any light".

[Lazarus]

Jammer, thanks for your input. I was working my way toward some of your conclusions and I'm glad we've been able to use Niemi's drawings to confirm what was found empirically. I remember my first inclination was also to make the sear face match the hammer hooks perfectly. Not hard to do, and - you're correct - the trigger pull is terrible. Very positive and unpleasant. If I remember correctly the pull weight was about 8 or 9 pounds. My reasons for taking the long way around were to establish a basis in mechanics for evauluating the different types of trigger pulls in general (well, the safe ones, at least). I know many people have developed a "method" that works fine, but unfortunately a descriptive method doesn't usually tell us anything fundamental, and often makes unclear or incorrect assumptions at the outset.

Referring to Niemi's drawing #2, it is point B that causes the heavy trigger problem. In other words, point B, whether or not a secondary cut has been made to the sear) will lift the hammer as the trigger is pulled. If you are dealing with very small hammer hooks (.016 - .018), with a 50-50 relief angle on the sear, you can get a reasonable trigger pull. It will be safe (see earlier), but the sear metal will tend to get mashed up fairly quickly. On the other hand, if your hooks are conservative (.025) and 100 % of the sear face is in contact with the hammer, then you will have a pretty hard time pulling that trigger. The trade-off of course, is that in the latter case, your heavy trigger pull will never "wear out" or become unsafe with use.

In my opinion, making the sear face angle resemble Figure 1 is the solution. With the one stipulation: the sear tip "A" is slightly shorter than the hammer hook. In effect, producing the angle in figure 1 prevents point B from lifting the hammer and places most of the stress on "A". Since A is closer to the hammer's tip, the amount of creep in the trigger will be less as well. (More to be said on this a bit later).

Also in the realm of opinion: the trigger at figure 3 can also work, but has a lot of built-in creep (or feel). And, the argument can be made that figure 3 is ideal for building a roll trigger, since a roll trigger is all about "feel". Maybe or maybe not.

Firgure 3 is not necessarily better or worse than figure 2, but I would have to convince myself first that the figure 3 engagement would not "stage". In other words, if the trigger pull stopped with point B halfway toward hammer release, would the hammer and sear remain in this 50% condition?? (i.e. an unsafe and undesireable situation). Avoiding "stage" in a 1911 trigger: how to do it? I know Gbw has got a handle on it.

Some triggers are specifically built to "stage", i.e. a 2-stage rifle trigger. That's another topic and we won't try to go into it now.

This question propels the discussion into yet another mystical arena, but fun nonetheless. It is the question of what happens after the sear starts moving?

I must qualify some earlier statements that were partially incorrect. In previous posts I stated that friction is the only thing that can hold a negative trigger engaged. I was thinking of evaluating the parts outside of the gun, with springs removed. In the real world with a fully assembled gun, a negative trigger is held in engagement by 2 forces: 1) friction and 2) sear spring force. Removing the sear spring to check the engagement will almost always reveal whether you have an unsafe condition. If the engagement is negative (unsafe), pushing the hammer forward will kick the sear out of engagement.

Compare this former arrangement with a positive trigger. A positive engagement is held together by mechanics (inclined planes) resulting from the hammer spring force. Friction and sear spring forces can be totally removed without changing the basic qualities of a positive engagement.

-Lazarus

[niemi24s]

Hi Lazarus: No doubt due to my poor wording, the second sentence in the second paragraph of Post 63 contains an incorrect conclusion: Point B on the sear in Fig 2 of Post 58 will not lift the hammer hooks during disengagement. Point B and all other points on the sear nose (including Point A) are the same distance from the sear pin center - its center of rotation.

That's what the broken red line represents in these three roll trigger versions: It's the line along which the sear nose/hammer hook contact must occur during disengagement so that engagement is always neutral - the defining quantifiable characteristic of a roll trigger.

If engagement goes positive or negative during the disengagement process, then the trigger (by definition) is not a roll trigger. Or, so I think! Cheers

[Lazarus]

Hi Lazarus: No doubt due to my poor wording, the second sentence in the second paragraph of Post 63 contains an incorrect conclusion: Point B on the sear in Fig 2 of Post 58 will not lift the hammer hooks during disengagement. Point B and all other points on the sear nose (including Point A) are the same distance from the sear pin center - its center of rotation.

Ok, thanks. I was just being verbose and general in my comments and did not yet tackle the rounded sear nose issue. Jammer had brought up a point that he had made the sear nose exactly flush with the hammer face, which I also confirmed yields a very unpleasant trigger pull.

That's what the broken red line represents in these three roll trigger versions: It's the line along which the sear nose/hammer hook contact must occur during disengagement so that engagement is always neutral - the defining quantifiable characteristic of a roll trigger.

If engagement goes positive or negative during the disengagement process, then the trigger (by definition) is not a roll trigger. Or, so I think! Cheers

Ok, that is one hypothesis that we can talk about. I won't try to pin a name on what type of pull this would be - but let's say you have created a pull that is statically neutral (full cock) and stays that way during the entire pull. You won't have to deal with the mechanics of inclined planes because there will never be any lateral components working on the sear. Technically, your sear face would then have to be an arc relative to the sear's center. Assume the hammer load on the sear to be a point load for the moment. The only thing you have to consider is friction.

Friction is kind of tricky. There is static friction (sometimes called stiction), and dynamic friction. Things that are statically engaged tend to stay that way because the force required to start things moving is always higher than the force required to keep them moving. In terms of the "feel", a trigger will always require more force (however small) to start the sear movement than it requires to finish the trigger pull. So, there will be an energy bump at the beginning of the pull. A positive trigger will also have an energy bump at the beginning, since you are adding hammer lifting (work) to the job of overcoming static friction. Both the neutral and the positive trigger, then will start the pull in a similar way. OK, so far?

[gbw]

I've been interested in the whole thread, in an ethereal sort of way. Niemis' drawings and calculations are, as always, facinating. I wish we could prevail on him to combine and publish them.

I don't mind a bit of 'creep', if it's smooth and consistent, and results in a positive engagement, however slight. Maybe that is a roll trigger? I sure don't know.

I'm thinking that no trigger setup worth having will re-set itself if pressure is removed - the famous 'click test' for a safety fit would never reveal a mis-fitted safety if re-set occurred.

[Jammer Six]

I can't hear-- the result of a mis-spent youth. So the click test is a theory to me.

I have to use that round gauge dingus that I have on the table saw, and clamp the weapon to the saw, pull the trigger, and see if the hammer moves.

This would be a lot clearer if I knew what that thing is called...

The bottom line is my checks have to be visual, accoustic stuff just doesn't work. I'll never be able to work as a sonar operator.

[Canuck-IL]

I have to use that round gauge dingus that I have on the table saw ... This would be a lot clearer if I knew what that thing is called...

Do you mean a protractor? A usually semi-circular plastic 'ruler' laid out in degrees around its perimeter.
/Bryan

[Lazarus]

Jammer means a dial indicator. Or if he has the updated version it could be a digitial readout indicator.. Anyway, this is an acceptable way to judge the condition of your engagement. I haven't gone as far as Jammer with the dial indicator because I get enough information from the operation of the parts on a pin jig. I go for feel, but only after I determine that the engagement is not negative.

Gbw, I usually reserve the word creep to mean rough and unpredictable jerking motion during the trigger pull. If the felt movement is smooth, it is not a problem for the average shooter. In fact, many bullseye shooters prefer a trigger with creep as long as it is smooth and predictable. So there. One part of the definition of a roll trigger is a trigger with smooth and predictable creep.

That kind of movement can be achieved by making sure that your mating surfaces are smooth. Be aware that EDM cut parts are going to need some serious stoning to eliminate those nasty ridges. But how smooth should you go? Hmmm. Off on another tangent, I believe there is something to be learned by considering the surface finish (smoothness) of mating parts. Mirror polish? I'm not so sure. Think about pressing 2 wet glass plates together and trying to get them to slide.

There is always more. How inconvenient!

-Lazarus

[Jammer Six]

Yup, Dial indicator! :D

How on earth did you know? That was scary... :scared:

[niemi24s]

Could it be that the smoothness of a well-done roll trigger is due a lot to:

1. Roll trigger = neutral engagement
2. Neutral engagement = no further hammer cocking
3. No further hammer cocking = no further mainspring compression
4. No further mainspring compression = No added trigger jerkiness getting the mainspring and mainspring plunger a wee bit further down into the MSH

Yes Lazarus, there does always seem to be more. How terribly inconvenient!

[gbw]

On a gun with neutral or near neutral engagement, there will be no measurable hammer movement even if the safety is mis-fitted and the sear partially disengages. As the test is performed with a fairly hard pull on the trigger, to measure accurately the pistol must be very solidly mounted, or the dial base attached to the pistol, to have any chance of measuring hammer movement even if there is any. And then it may just be the parts shifting slightly on the pins, or the pins in the bosses. I'm not sure the 'click', or it's absence, is not a more reliable indicator.

[Lazarus]

Glbw, the thumb safety test is a back-door way of getting at the next point in evaluating trigger pulls. The thumb safety test will not work correctly unless the sear "stages" itself at a point outside of its statically cocked position.


I'm thinking that no trigger setup worth having will re-set itself if pressure is removed - the famous 'click test' for a safety fit would never reveal a mis-fitted safety if re-set occurred.

Ok, the part about the thumb safety test not working is true. But I'm not recommending that we rely on that test to give us information about trigger condition. The safety test "allows" a given trigger setup to assume a condition that cannot be duplicated by pulling the trigger only. (Hint, hint). Besides, the whole point of thumb safety adjustment is to prevent any sear movement in the first place. The clicking sound tells you only that the trigger has moved the sear with the safety applied, so you screwed up.

About the first part of your comment - no trigger setup worth having will reset itself - I'd reserve judgement on that one for the time being. If any trigger returns to its statically cocked position from a partial pull, the only fact we know is that the engagement is positive. And, a positive trigger is a safe trigger. Isn't that what we want?

I do not mean to say that all positive triggers will return in this way because it would depend upon the component of friction. Mentally remove friction - then you can say that any positive trigger will return to statically cocked position from a partial pull.

But in any case, let's look at how friction affects the actual pulling of the trigger. Is friction always a bad thing? Isn't friction what makes a heavy trigger pull heavy? Maybe we should bag the whole thing and convert to electric triggers. There's a thought.

-Lazarus

[niemi24s]

Hi Hotbrass: Curious to find out whether you attempted to create a roll trigger and, if so, how it came out - good or bad. Any instructive input will be welcomed, as I'm not sure (at least right now) if I'd ever want to try to make one. Regards.

[hotbrass]

Sorry niemi24s, but I have been on the road and have been in New Mexico for a week. I am shooting the Cowboy Rifle Silhouette National Championship this week and will be back home on Saturday.

I started work on one and it feels good. It is basically a long smooth pull with no hint of letoff. It is just a straight long trigger pull with no drag. My only task now is getting it back up to BE legal weight which wont be too hard. I just havent done it yet.

It simply involved a lot of polishing. Dont ask me about angles or any of that stuff, it is just smooth as butter with no hesitation from start to letoff.

Carry on!

[niemi24s]

Glad to hear it came out the way you wanted. Best of luck at the meet.

Carrying on!

[Lazarus]

Let me mention a couple more ideas as a wrap-up. I'm concerned that others might be asleep by now and find this approach boring. It was not my intention to do a manual on "How to make a Roll Trigger"; but merely to introduce some of the concepts that are at work in the trigger mechanism of any kind of firearm. My generalized approach seems warranted because the overwhelming number of posts asking about trigger work show us that a great void of understanding exists, especially among "do it yourself" gunsmiths. What is also amazing to me is that we can be discussing trigger basics in one thread, and receive several other general questions on trigger operation right next door. I suppose this says more about attention spans than anything else.

I have referred to trigger energy diagrams previously but we haven't drawn them. For reference purposes, here are a few diagrams of various triggers, in this case on a Savage rifle.

Trigger Energy Diagrams ( http://www.shootingtimes.com/longgun_reviews/STsavage_0813E.gif)

These diagrams show trigger pull weight along the Y axis and trigger movement (or creep) along the X axis. They are interesting to us because they give us a way to refer to various types of trigger pulls. Obviously the last diagram is going to show us the idealized "clean break" or glass rod break. Trigger pressure increases steadily with very little trigger movement, then breaks abruptly.

Diagram 4 would be an example of a smooth creep trigger. There is "feel" as the trigger is moving to the rear and the pressure on the trigger must steadily increase after the pull has been started (static friction is broken). This trigger may in fact reset itself if pressure is removed during the pull. This is the graph of a positive (and safe) trigger. Note that one of the qualities of this trigger is that when the apex is reached, there is a clean break as seen by the almost vertical drop-off.

Diagram 5 is interesting because it represents a mostly negative engagement trigger. After static friction is broken, there is a sloping section. The trigger must move further backwards, but the required force is actually diminishing during this part of the pull. In order for trigger force to diminish in this way, the trigger engagement (before hammer drop) must be negative. Another way to put it is to say that in the negative pull area, the hammer spring force "helps" the trigger pull because of the mechanics of inclined planes. There is a very small positive bump just before the trigger falls that saves this trigger from being technically unsafe.

Diagram 1 comes closest to what I would call an etheric roll trigger shape. Once static friction is overcome, there is a plateau region where there is trigger movement to the rear, but the force required to keep it moving remains constant. It is not known whether this type of trigger will stage halfway along this plateau. But there is the required "feel" with none of the ill effects of a negative trigger pull.

This particular concept - staging - is usually not a problem with 1911 triggers because of the fact of static friction. Because it takes more force to start the trigger pull than it takes to keep the parts moving, the first part of a real world trigger pull will actually be felt as small jump when the sear begins to move. Crisp breaking triggers are cut to insure that the sear will either jump completely outside of the hammer hooks on the initial stiction break, or the engagement will change to negative after the sear jump and the hammer force itself will complete the trigger pull.

Smooth creep and roll creep triggers try to minimize the feel of the sear jump and provide some predictable "feel" to the trigger pull - beyond the initial static friction break. Remember mention of surface finish? Judicious choice of finish can minimize the energy peak that is realized during the initial static friction break. I'll just suggest that mirror polishing the parts can actually cause that energy peak to be more pronounced, not less. Something to ponder in any case.

Finally, thanks already to gbw for these ideas, the mechanical attributes of the engagement can change during a trigger pull. Positive or neutral static engagement is desired, however after the initial sear movement, the engagement angles change and if they change to negative you will have a smooth breaking trigger, though not necessarily a crisp "glass rod" break. This type of trigger is perfectly safe because it is positive or neutral in the initial statically cocked position.

While a neutral engagement is techncially "safe", this condition bears close watching. Neutral engagement exists in a precarious balancing act between positive and negative. Wear between the parts always tends to move a neutral trigger towards negative - entropy at work. Thus a neutral trigger should be regarded with care and checked often. Having said that, I have noted that the great majority of custom 1911 triggers are neutral. It is otherwise difficult to get below 6 or 7 pounds. Jammer can add a bit more here, because he checks the triggers with a dial gauge.

So, for those who want some ideas before they hack away at expensive parts, I think we've touched on a few good ones. For those who prefer to just start making the pizza, you can still have a good time, especially if you accidentally produce a great trigger pull. Accidents do happen, and we can learn a lot from them, to be sure.

-Lazarus

[berkbw]

Personally, I don't think so.

I still don't think anyone has taken a stab at describing what a roll trigger really is. So, unless we have a definition, we won't know if we have one....

Now, safety is primary as it should be with any trigger work. That means that the hammer will stay statically cocked and will not fall if the gun is bumped. That also means that in the statically cocked position, the engagement is positive. That's a technical term, by the way...positive.

But what happens when the trigger is being pulled? That is, the sear is moving, but the hammer has not been released. We do not want the trigger to stage. In other words we don't want it to halt mid-way along the hammer hooks while we reconsider the meaning of life and the validity of our sight picture. On the other hand, we want some "feel" to the trigger pull, not just a sudden and abrupt hammer fall, without any percieved movement in the trigger.

So, what is it that we are trying for...? Some might call the rolling break just another term for trigger creep. And they would be correct, mostly. But creep is usually a coarse and unpredictable jerking movement as the trigger is being pulled. Nonetheless, there is still a perceived movement between hammer and sear during the trigger pull...but it must be made smooth. There is more to the story. Anyone care to elaborate?

-Lazarus

Sir - I read a post above, and followed the links in the linls, and ended up at Brian Enos's site. There is a thread there which "should" define things for you, with several pros chiming in.

Now, actually, I could explain to anyone my understanding of a roll or rolling trigger, fit and function. You would be better served, I believe, to read the thread yourself, as my interpretations and yours would no doubt diverge.

Best Regards
b-

[berkbw]

A "Roll" trigger simply means that the sear angle is rounded at its tip. Properly done, there is no cocking or decocking of the hammer during trigger pull. It yields a VERY soft break.

Read the thread on BE's forum, it is pretty good.

(OOPS!) BE=brian enos googleable.
b-

[hotbrass]

I thought this thread had ended when old Laz wore his fingers out trying to type his way to first base.

Roll triggers are great! I just decided I dont like them. I prefer a crisp glass-breaking trigger. And I didnt have to puke up my physics and geometry lessons to figure it out.

Carry on! :dead_hors Again!

Best regards Lazarus!

[Jammer Six]

So, how do you make a roll trigger?
:dead_hors