More Measuring

[gbw]

Too much spare time today…and, since 1911Tuner and Nieme24s solved the unsupported brass problem so efficiently, I thought I'd pose another. May be useful for all of us hobby builders out there.

I want a method and formula to time a 1911.

That is, I'm scratching my head to find a reliable way to know the MINIMUM distance down the barrel must have moved when it hits the VIS in any pistol.

AND I'd like to know how far the rear the barrel must move to get it down a specified distance (for example, [(lug engagement depth) + .008]).

The Schuemann method to measure minimum drop should work, but for me has not been that reliable, especially if the slide has any play. If there is a better way to directly measure this minimum drop, i.e. with all link slack pulled out in the tension direction, then we don't need to calculate it and we can happily blow off and forget everything below. If not (and maybe I’m making this harder than it is??)………


If we know both how far the barrel has moved back at VIS impact (this is measurable), and how far it must move to get to a given downward distance, then we know whether or not the VIS must be moved rearward, and how far, to avoid a crash plus give a bit of clearance.

[N.B. If the VIS is already too far to the rear then there is no VIS impact. In that case 1911Tuner says something will break, so count on it. So the frame bridge and rails must be lowered, and/or other downward barrel obstructions removed in the slide and/or barrel feet, until VIS impact is achieved.]

We know the following (and let's assume a hard-fit barrel):
a) the horizontal distance from the slide stop to the VIS
b) the maximum distance (including clearance) between centers of the link - this is fairly easily measured.
c) the depth of lug engagement at full lockup.
d) we can measure fairly well (?) the horizontal distance from the link hole to the rear of the lower lug.
e) we can measure, although it's not too easy, how far to the rear the barrel moves to VIS impact.
f) do we know the nominal angle past vertical for the link in a spec gun? Is it even significant?

Which brings us to...........

Things we don't know:
a) the exact position of the link in any specific gun at full lockup - at least I don't think we do. Without knowing that we can’t calculate the downward movement before VIS impact. In most drawings I've seen it's slightly past vertical.

b) We also don't know the position of the link within it's range of motion between the pins, because of a).

If there was a good way to get both of these values, it's simple – first figure how far back past vertical to remove slack, then how much farther to be pulled down a given distance. But I can’t think of a way to find those values. Maybe the best I can hope for is to use a reasonable ‘worst case’ and work from there.

Sad to say no one has ever published a set of tables for the various link angles past vertical, link lengths, and ss-vis distances, and showing downward movement! If any of you programmers out there need a project…

[niemi24s]

Hi GBW: Have you ever built a really big "stick and paper" model airplane from a kit? Amazing how the days turn into weeks with one!

:lm:

[gbw]

Nah. I've been threatening this for years, once I get these goofy guns figgered out I'm gonna build a real airplane from a kit (probably Europa). And fly it!

[Iron bottom]

I'm no math wizard like niemi, but you know the radius of the arc of the link. I'm sure there is a computer program that will do the math for you. John Browning found this out somehow. The figure accepted for the slide movement before the barrel begins to unlock from the slide is .010, but I could find no info on the drawings I have. If I'm not confused the slide must move this distance past the links vertical position after going to battery. Slop in the link will likely alter this some. I just stick a piece of tape on the slide and eye ball the the link pin hole in the barrel's lower lugs, mark it on the slide, and compare it to the slide stop pin, also checking the thumb safety as the lugs are cut. Crude...Yes, but will get you close. On a really tightly fitted pistol such as a Les Baer I believe this (the link going vertical and binding a little before heading down hill as it passes vertical) is the cause of the slide hesitating right before going fully to battery. That would be some nice info to have.

[niemi24s]

I think the dimension given as ".010" in the second line of Post #4 should be ".10" [doggone decimal points!]. Anyway, the only readily available data I've brewed up pertains (sort of) to gbw's "things we don't know a)", link position at battery.

Based on RIA blueprints, a mid-spec USGI 1911's standard 278 link will be in compression at battery and its hole-to-hole centerline axis tilted about 8.7 degrees past the vertical.

However, gbw was pursuing this for a gun with a hard fit barrel, and that changes everything with the introduction of different link lengths and the gun-specific distance from the slide stop pin to the barrel link pin (after the feet are trimmed for a tight riding-the-pin lockup).

Then there's the question of "Exactly how loose is the link in battery in a specific gun with a hard fit barrel?" Not to mention how to measure any of this. Food for thought, but my head hurts.

[Iron bottom]

Caught me, niemi. :D

[niemi24s]

Glad to oblige, Iron bottom. I used to make lots of these same kinds of goofs until someone suggested (for quantities less that 1) to always place a zero to the left of the decimal point. Got absolutely no idea why it helped. But, I make a lot less of these errors since starting to write 0.0123 instead of .123 (oops) .0123. Dang! Did it again!! Cheers. :)

[niemi24s]

I couldn't find a stick and paper model airplane kit to keep me occupied either, so here's one way find the "link" position in full lockup for a specific gun, as in gbw's "Things we don't Know, a)". I put link in quote marks cuz this procedure finds the position of the barrel link pin in relation to the slide stop pin, and the angle. With a hard fit barrel, the link is (or should be) a little loose in full lock-up anyway, so the pins that restrain its movement are the only things with fixed positions.

To make the measurements you'll need a slide caliper with OD jaws thin enough to fit into the link slot between the barrel feet, plus a set of numbered drills (or a pin gauge set).

1. Remove the barrel from the gun, remove the link pin and link.
2. Measure the OD of the barrel link pin and reinsert it (no link) in its hole. This is measurement D, as shown below.
3. Take the rest of the measurements, then do the calculations shown.

http://i129.photobucket.com/albums/p232/niemi24s/P3310002a.jpg

Some of these measurements require a considerable amount of finesse, such as A and B. You'll need the numbered drill or pin gauge set for E.

Even with good measurement techniques, the measurements and the quantities derived from them will, I suspect, have rather large uncertainties. F'rinstance, if G is off by 0.001 inch, the angle will be off by 0.2 degree. I'd estimate the angle's uncertainty at about +/- 0.4 degree - even with the very best measurement techniques!

[Edited: Also, the calculated angle is referenced to the barrel axis. If you want to find the angle referenced to the top of the receiver you'll have to add the angle between the barrel axis and receiver top when in the battery position.]

[Lazarus]

Thanks for digging out dimensions and numbers, because I think that referring to the original ideas is a great help in understanding. They serve as a reference point for doing the real work, which is actually magic, not measurement.

I have found that correct numbers and careful measurements will get you about half way there. The real work is in the areas that are not readily measurable, and you have to rely upon feel, sound, and experience. Hmmm, you say! ...these methods don't seem very scientific to me.

A quick example: a well-known 'smith fitted a Kart NM barrel to a Vermont slide for me some years ago. Examination now reveals that there was little attempt to optimize the upper lug engagement, causing the barrel to sit rather low when in battery. No problem! A Wilson lug cutter trimmed the barrel feet off very near to the link pin hole, making the bottom lug almost square in shape. No problem! Simply open up the slide stop hole in the link pin about .020" to allow the slide stop to maneuver around the square corner of the lower lugs. And the story goes downhill from this point. Sadly, this is how a lot of guns get made. How will these builders improve, even if they have a valid set of dimensions? My answer: by magic.

Niemi, I wonder if you have seen a drawing - similar to the one you just posted - that shows the arc of the barrel lug swung from a point slightly removed from the center of the link pin? This is an attempt to explain how a hard lockup can co-exist with the idea of a smooth link-down. The center of the lug's arc is placed about .010" away (choose your direction) from the center of the link pin. Even if this method seems to make sense, I challenge someone to somehow prove that he has fit the parts with this amount of measured precision. The difference between an acceptable fit and a great fit is about one filestroke - usually. That's what I'm trying to say.

-Lazarus

[niemi24s]

Hi Lazarus: No, I haven't seen the drawing you mention in para. 3., but sure would like to. Big ++ on your para. 2 comment: the calliper and micrometer can get you fairly close to what's needed, but relying on them for the final strokes of the file is asking for problems.

Guess the reason for doodling like this is I'm still trying to learn how this thing works, and these sorts of visual aids have really helped. They're the next-best thing to a large scale mockup, IMHO. Cheers.

[Iron bottom]

Nice work, niemi. The only way I see to get a smooth lock up is to fit a link that is perfectly tensioned in lock up, and enlongating the link pin and slide stop drillings toward the center of the link to allow the barrel to move rearward without lifting and binding the pistol up. However, there is some clearence built in the link, and this may suffice. The trouble with links is that you can never find one that fits properly. I suspect you may want to locate your VIS torturing tools and some packing materials before fitting a long link. :D I do think this is possible, but not a kitchen table job. Lowering the slide and frame bed may also be required. And possibly working on the barrel ramp.

[Lazarus]

Niemi, I'm looking at a drawing that is part of Ed Brown's 1911 handbook. He locates the center of the arc of the barrel lugs .010" toward the rear of the link pin center (rear of the gun). A .183" - .193" radius is swung from this point. Now draw in the arc that represents the inner-most surface of the slide stop hole in the link.

You can see that, theoretically, the slide stop will wedge into the barrel lug as it approaches full battery. But putting it another way - if you could actually cut it this accurately - the slide stop would be riding the link everywhere except where the link is nearly vertical. I'm not a fan of this type of imaginative engineering, but it is interesting to consider Ed's idea. Ed says he cuts all his barrels this way. Perhaps if you machined your own barrels, slides and frames (like he did) it would be possible to keep most of the variables at a minimum and actually produce a working barrel "fit" using a rotary table and a mill. I don't think you and I will be cutting our barrel lugs that way, however.

-Lazarus

[niemi24s]

Hi Iron bottom: The slop between each hole and its pin (mid-spec) adds up to about 0.0075 to 0.0080 inch. Over- and under-sized links by Marvel are available in increments of 0.003 to 0.004 inch, but I suppose even if you had an assortment of all of them one might a bit too short and the next-longest a bit too long. 1911 Tuner posted some hole elongation limits he uses, but I can't recall what they are.

In regard to moving a VIS back, I'd never do it unless it was out of spec. To me the receiver IS the gun, and if a barrel's feet contacted the VIS too soon, I'd not hesitate to file down the aft surface of the feet - in spite of what Schuemann says. But, I've never run into a can of worms like this, so I'm not speaking from experience - just my gut feeling.

[niemi24s]

Hi Lazarus: Guess the Ed Brown way is one way to do it. I might be wrong, but had always thought the best foot profile allowed the slide stop pin to support the barrel until just before the link went into tension to pull the barrel down. This means the flat area on the feet would extend about 0.040 inch forward of the link pin hole centerline. Maybe this is good in theory, but unworkable in practice because . .

. . . then the barrel top/slide clearance issue and all the other post-barrel unlocking issues come into play. All this, I guess, mandates an inevitable compromise somwhere to get the gun to work.

Thanks for the Ed Brown data. Will noodle with it a bit later on. Cheers.

[Lazarus]

I'll just note that if you look carefully in J.K. volume II, there are a number of drawings that indicate something similar to what Ed Brown was explaining. Sometimes you will see an added center point without dimensions. The position of the offset center seems to vary, if present at all. Lots of dreaming going on, I think.

As far as the comment about adjusting the VIS, let's make something clear right now. There is no ONE thing that can be "out of spec", with all others being "in spec". Normally, you must identify a functional problem, such as: stem binding when feeding ball ammo. Then, you might have half dozen individual dimensions that could contribute to that problem. The solution is usually non-specific. Deep meditation, luck and magic are all involved.

-Lazarus

[gbw]

Hi Iron bottom: The slop between each hole and its pin (mid-spec) adds up to about 0.0075 to 0.0080 inch. Over- and under-sized links by Marvel are available in increments of 0.003 to 0.004 inch, but I suppose even if you had an assortment of all of them one might a bit too short and the next-longest a bit too long.

And I've found this to be true. So I use IB's method of finding a link that works for full battery (you can feel the snap as it passes through vertical), and elongating the link pin hole toward the center - only .001 - .003 needed. Since we prefer not to ride the link into battery the elongation is no issue.


In regard to moving a VIS back, I'd never do it unless it was out of spec. To me the receiver IS the gun, and if a barrel's feet contacted the VIS too soon, I'd not hesitate to file down the aft surface of the feet - in spite of what Schuemann says. But, I've never run into a can of worms like this, so I'm not speaking from experience - just my gut feeling.

I've done, or tried, both. VERY hard to move the VIS back. You can remove the bow-tie with files, which buys .003 - .005 horzontal at best, or .002 - .0035 in vertical clearance. After that, a mill and expert experience is needed, neither of which can be found at my place. So I then trim the rear of the lug - you can put the barrel in a lathe and cut it back very accurately, even a small hobby lathe, which I do have. I also limit this to .006 or so. Between the two, I get link down adequate clearance. I also put the Schuemann relief on the bottom half of the feet to prevent them from impacting in that area, and then must to re-do the gusset so stress risers are not created. I have ended up with barrel feet at .090 or thereabouts at the narrowest point, but this has not created any problems so far.

[niemi24s]

Digested what Iron Bottom and Lazarus said in their posts #11 & 12. It seems my previous concept of having the feet bear on the slide stop pin for about 0.040 inch beyond (forward of) when the link is vertical is impossible in reality.

Wish I had some junk/beater 1911's to experiment with, cuz it's been decades since I hard fitted a barrel. Did it with little knowledge of how the 1911 worked, and did it without the benefit of a "lug" cutter and all the mikes and calipers I currently have. Paid $10 for a NM barrel & bushing and just kept filing on various things until the gun functioned and locked up nice & tight. Luck was on my side.

Anyway, I'm still in the process of trying to figure out how long the flat spot on the feet can be - in theory. My NM barrel doesn't look like it has a flat spot at all, so it's no doubt closer to Ed Brown's way than my initial pipe dream.

Thanks, Iron Bottom & Lazarus, for getting me thinking on this - again. Cheers.

[Iron bottom]

Well, Niemi, I haven't seen a factory colt that even had the lower barrel lug sitting on the slide stop pin. I don't really see why it is necessary to have much of a flat spot since the barrel and slide are locked together until the bullet leaves the barrel. You can drive the link pin partially into the bottom barrel lug and place the link on the outside of the lug, Dykem the lug and use the link as a "compass" to swing and scribe the arc of the link on the lug and remove the excess. Do both sides, of course. Gets one fairly close. I'm beginning to think like you, Niemi. If you have a good frame and slide, keep them tools in the drawer. Getting these two items is 99% of the ball game.

[niemi24s]

All this stuff was based on gbw's Post #1 in which he talked about a hard fit barrel. I assumed he meant one supported in battery by the feet instead of the link, like a mid-spec USGI 1911.

Don't know if the feet really "need" to have any flat spot on which to ride the slide stop pin out of battery. As you said, internal pressure's supposed to lock the barrel & slide together until the bullet's gone. However, I think if you use one of those little hand-cranked lug cutters Brownell's sells, the feet will end up being cut with a flat spot. And, depending on how much extra metal was in the feet, this flat spot might extend forward of the link pin hole centerline. If it extends too far forward, the link would start to pull down the barrel, but the barrel couldn't be pulled down - binding it up.

Just completed noodling with sketches & the calculator. Found for a standard 278 link that's just on the verge of compression when vertical, the barrel (and slide) can travel aft about another 0.052 inch before the link comes under tension (due to an excessively long flat spot) and binds the slide stop pin up against the feet. Combined with the about 0.041 inch of travel between between battery and the link being vertical gives a total travel of about 0.093 inch from battery before barrel pull-down will start.

This (barring math error) is the theoretical limit for barrel support by the slide stop pin - with a 278 link on the verge of compression when vertical. Does it need all 0.093 inch of it? Does it need any of it? [does Howdy Doody have a wooden leg?] Regards.

[Edited: If the locking surfaces of the barrel and slide weren't nice and vertical, but were tilted back at their tops slightly, it seems to me internal pressure would tend to "cam" the barrel downward after firing. If so, wouldn't the longest possible flat spot on the feet help keep the barrel up against the slide? I know they're supposed to be vertical, but what if they're not - perhaps due to a poor job of filing the barrel lugs?]

[gbw]

This is, I think, 1911Tuner's famous .100 slide movement before linkdown barrel drop begins. It seems to be important in order to get the bullet out of the barrel, and hence allow pressure to drop away, before extraction begins. If there is a max / min specification for this travel I've no idea - there must be a minimum, and actually I can't think of a reason for a max.

Conventional wisdom says to leave the lower lug 'flat' as long as possible. Of course the flat can only exist at all if there is link slop. And, I suppose vertical slide / frame clearance, which wouldn't help accuracy. Anyhow, sometimes conventional wisdom is wise, sometimes just conventional. To the extent that the barrel really is locked to the slide via opposing forces through the lugs, I can't see where the flat would matter much.

[BTW - All of the stuff in the first post is indeed assuming a hard-fit barrel. To me that means, in battery, no clearances. A contact fit between the barrel lower lugs and slidestop pin, and between the barrel first lug recess and the first slide lug. With Schemann barrels this upper contact seems to be a continuous area from about 10 to 2 o'clock. (Schuemanns also need a #5 link with Caspian ss frame / slide!! .291, I think, and very very little linkdown clearance.) With Kart NM barrels, it's a sort of a contact pad at 10 and 2.]

Thanks, guys. I'm enjoying this thread also.

[niemi24s]

The 0.052 inch mentioned in para. 3 of Post #19 is the practical limit for this segment of the flat spot. With a really long flat spot, the slide stop pin will contact it and bind 0.067 inch past the link-vertical point (or 0.108 inch from battery). However, the transition between the flat spot and the curved front section of feet needs to start before this binding point because the link is rotating beyond vertical and its motion is not tangential to the flat spot (is headed up about 22 degrees from the flat spot).

Anyway, I reduced the 0.067 by the length of the transition needed, estimated from my large-scale drawing to be 0.015 inch. Hence the .052 inch posted.

[Edited: Here's a sketch illustrating my gibberish. Note that this is nothing more than a analysis of what's possible under the stated conditions. It's not how my gun is or how anyone else's gun should be, ought to be or needs to be!]

http://i129.photobucket.com/albums/p232/niemi24s/P4030004d.jpg

[Iron bottom]

Yep, Niemi,the barrel is held in full lock up while the lugs are cut with this particular tool. But with the cutter being only .196 there is still some hand fitting required to fit the link. Namely getting the slide stop pin to turn the corner. I can see where a bottom barrel lug not sitting on the slide stop pin with the link in tension would tend not to stop at the same precise height each time. I do get some vertical stringing on some of the guns I have and believe that the lugs not sitting on the slide stop pin contribute to this stringing. But maybe not. Nice work, BTW.

[niemi24s]

Under the conditions of this analysis, with the 278 link on the verge of compression when vertical, the link is loose in battery. With the dimensions shown in the sketch, a 273 (or -5) link would be needed to be on the verge of tension in battery.

Is the link supposed to be in tension in battery?

[gbw]

Very light tension would be prefect - it allows smooth unlocking, and true hard fit through the slidestop pin-barrel-slide, and still gives the earliest possible linkdown, so the barrel-slide clearance is maxed before vis impact. Provided, of course, that there is adequate rearward movement before linkdown begins. .090 - .110" I think is what Tuner recommends.

Light compression would be helpful in the case where the VIS was slightly too far to the rear. A better solution in that case would probably to lower the frame bridge a bit.

[Actually I hope 1911Tuner is following this so he can correct us if / when we get off track.]

[niemi24s]

If 1911 Tuner gives a figure of 0.090 to 0.110 inch of travel before link-down begins then I must not have made any math errors - at least big ones. The position labeled "bind" in the sketch is where the link just comes under tension (and linkdown thus must begin). The 0.108 inch dimension is the theoretical slide travel from battery to binding, so I guess it's in the ballpark.

My next quest is a simple method to lock the barrel quite forcibly up against the slide so this distance can be measured with some reasonable degree of precision. Tried it with a rod down the barrel (like in the Schuemann tests) but that darn little link exerts too much downward force to resist by hand - and still be able to take the measurement.

Thanks for the info. Regards

[Lazarus]

I'd like to suggest that the concept of a "flat spot" on the lower lugs may just be hyperbole. When looking at a nice big drawing of the link and lower lugs, then it seems more logical to talk about flat spots. Especially true if the barrel lug radius is cut on the same center as the link pin. But, using the concept of 2 different radii, then our drawing changes to something like a wedge instead of a flat. Conceptually, image of a wedge is more attractive.

Perhaps the idea of a flat popped up about the same time that lug cutters came into fashion. The lug cutter will in fact cut a flat onto the barrel lug. Even though this tool can be a time saver, it can also be abused if you don't understand what you are trying to do. If any type of tool - other than files and scrapers that is - is going to be useful it will be a rotary table mounted on a vertical mill. Then, you will get a radius and not a flat.

I think we all agree that the barrel feet should stand on the slide stop pin in battery. A number of things have to co-operate at that exact point which would include link tolerance, slide stop tolerance, and the final 'hard fit' of the upper lugs into the slide. The upper lugs may equalize a little, or seat a bit differently after firing, and that tiny bit of change will throw off your most precisely orchestrated 'flat' fit at the lower lugs.

-Lazarus

[niemi24s]

Thanks Lazarus - more food for thought. As Iron Bottom mentioned, the lug cutter has a 0.196 inch diameter. Never used one, but can see the final trimming of the cutter's flat spot (to accept a slide stop pin about 0.004 inch larger) would probably end up turning the flat into some radius. At least it would for me when doing it by hand. Never could keep anything flat with a file! Cheers.

[Iron bottom]

That extra bit of metal the cutter leaves may come in handy. A slide stop pin that is a little under spec may fit very well. Plus you may experiment with a longer link since you can always go to a shorter link . Dawson Precision has links in 0.0015 increments instead of the normal 0.003 if I remember correctly. These can save a lot of work in some situations.

[niemi24s]

Thanx Iron Bottom - Dawson's now in my Favorites folder.

[auto45]

I enjoy reading threads like this, learn a lot.

I'm also glad the design works with less than ideal barrel fits, because this type of precision will never be seen in production guns. :D

[gbw]

That the truth! A lot of hand fitting, plus a little luck. Anyhow...

Using the .196 lug cutter (until the disconnector works) leaves nominally .002" to remove with a .200 slidestop. My experience with the cutter is that it leaves a bit less. At that point filing is out, and I use 400 sandpaper (single layer) around a .195 brass rod. Rub over the flat til you can force the gun into battery - it doesn't take much. THen the last part of the fitting is done with a .200 piece of brass, with a recess machined the width of the barrel lugs and just slightly thicker than the paper. (The only machine tool I have is a small hobby lathe, used to make the tool). Using this tool is a major pia - cut 400 paper to the same width as the recess, and just long enough to wrap around it once. Super-glue in place. Put barrel in slide, slide on frame. Insert the tool and twirl it to 'seat' the barrel on the 'pin' (tool). It normally takes 5 or 6 paper replacements, each time cutting and gluing the paper on the rod. This also cleans up the radius to match the slidestop. If everything is done right, including the upper lug fitting and engagement which comes before all of this, the result is a very tight but smooth lockup, and a pretty accurate gun.

Then it's time to time, which is where we came in....my exp. with match barrels is that there is usually not enough link-down clearance, but I'm a hobbyist and maybe I've missed something. But the ideas and calculations from this thread will be a big help!

If someone has a better way to final fit, without a milling machine and the skill to use it, I'd sure love to hear about it.

[Lazarus]

I know this is obvious, but... the lug cutting tool has 2 sizes of cutters, a .196 and .198. These sizes bear no relationship to the theoretical shape of the lugs, aside from the fact that the slide stop pin must fit into the gun. .198" cutter is about as large as the tool can be without chewing up your slide stop pin hole in the frame.

Any sized cutter will still cut a flat onto the lugs; technically, that is the only possible outcome. But even after using the cutter, you have to shape the lug radius. Look back into the barrel fitting stickies. It makes loads of sense to read about using precision pin stock with a little lapping compound to help in the final seating process. This method is a fine tuning procedure that is limited to the fully in-battery position of the slide. You are creating a nice snug fit at the in-battery radius of the lugs. Whereas, whith the lug cutter procedure, you are making a gross or coarse fitting step requiring more work to clean up the mess that you just made.

So, since most of us are interested in doing things the right way - not just the quickest way - I would say that selling the lug cutter on Ebay, and practicing a little extra scraping and filing technique would be a good thing.

-Lazarus

[gbw]

I don't know, Laz. For me the lug cutter, it comes in .186 and .195, gets you close without going over. (I only have the .195, and I had to insert a roll of .001 shimstock into off-side bearing to get rid of some slop.) It also does cut the preliminary flat and radius. Still handwork to do to finish fitting, but it saves time and reduces the probability of gross error, in my case a consummation devoutly to be wished. Of course you must lock the barrel tightly into the slide, perfectly centered, before using it. I made gizmos to both lock the barrel in and center the lower lugs.

[niemi24s]

As long as you two gents are discussing lug cutters, perhaps you could satisfy my curiosity. The one in the Brownell's catalog comes in two sizes, 0.186 and 0.195 inch diameters. The Brownell's description sez use the 0.186 first, then the 0.195 cutter "if more material needs to be removed."

After using the 0.186, how can more material NOT need to be removed?

[gbw]

In their instructions with the cutter they say that in some cases the .195 cutter is too large, and the smaller cutter should be used first. How this can be so with a slidestop of .198 or larger, they don't say and I don't understand either. That's why I have only the .195 cutter.

[BTW - in their catalog they also have a method for making springs. Last step is to set the spring on a dented-in can, cover with motor oil, and then set the oil on fire and let it burn off for final tempering.

Try it. Then let me know HOW to set the oil on fire, cause I'm not sure it's possible.]

[niemi24s]

Thanks for the info, gbw. Perhaps the 0.186 cutter is for those new-fangled "undersized tactical titanium tritium slide stops" (for easy reassembly in the dark) some yokels were talking about at the range last week.

:lm:

Never tried making a spring myself, but recall reading about this same sort of thing years ago. The author said to light the oil with an acetylene torch. I think maybe a propane torch might do if the quantity of oil wasn't too great. Sounds like an outdoor, downwind job, huh? Cheers.

[gbw]

Thanks for the info, gbw. Perhaps the 0.186 cutter is for those new-fangled "undersized tactical titanium tritium slide stops" (for easy reassembly in the dark) some yokels were talking about at the range last week.
Cheers.

Too hi-tech for me. Now when they get one that assembles itself, I'm in.

One long cold winter day years ago I DID try lighting the motor oil with acetylene. Did not work. Smokes, but does not ignite. Melts can, makes mess.

[niemi24s]

Hmmm-m-m-m ...... Only other thing I can think of is maybe a little tuft of oil-soaked rag to act as a wick. But, it'd probably just sit there and smoke like crazy for a few hours without lighting the main pool of oil. Maybe thinning the motor oil with fuel oil (kerosene or diesel) would help get it started.

Interesting problem. After the snowstorm quits, maybe I'll give it a whirl. Let's see ... thermite is what part aluminum to - no, burn hole in can. How about some Bullseye? Nah, burn too fast. Hmmm-m-m-m.... Cheers