Lower Link Hole Clearance

[Semi-manual]

How much clearance should there be between the slide stop pin and the lower link hole? Mine seems awfully sloppy; I can see daylight when the pin is inserted in the link (barrel out of the gun, of course). I know that this can cause timing problems if excessive, but how can you tell and what is excessive?

[niemi24s]

Play between the pins and their holes are required for proper linkdown timing as shown here: http://i129.photobucket.com/albums/p232/niemi24s/scan0003atxtc.jpg Some manufacturers of longer-than-normal and shorter-than-normal links make the slide stop pin hole (the larger one) a bit larger than normal, but I don't know how lmuch larger.

[Semi-manual]

niemi24s: Thanks for the drawing. I took my link and measured it and found the large hole to be elongated .221 dia. along the axis between holes and .219 perpendicular to the axis. The small hole maesured .158 dia. Calculating the center distance between holes put it at .285 (.475 across both holes). I decided to make a new link and used the drawing you provided. I made it from 4140, hardened it and it's now in the oven being drawn back to about Rc 40-45. Is that what they are made of??

[niemi24s]

I decided to make a new link . . . Now that's the sign of a true 1911 afficiando - makes his own link! :appld: I made it from 4140, hardened it and it's now in the oven being drawn back to about Rc 40-45. Is that what they are made of??The blueprint in our Tech Issues sections says 1075 through 1085, and the most current one says 1075, ASTM A684. Both say Austenitic grain size 7 or finer. The most recent print says RHC 39.5 to 46.

You should be aware of the possibility the original link in this gun was either a non-standard length to begin with or someone had fiddled with the holes to get it work in the gun. There are lots and lots of links longer or shorter than the standard 278 link in the pic. Just make sure the link you're making is indeed the correct one for your gun.

[Semi-manual]

niemi24s: I have the article by Schuemann Barrels on how to test the timing but I have not been able to come up with the drawing for their tool which replaces the spring in the test kit. They said the tool is described in the barrel installation instructions but I haven't been able to get a copy and I don't want to buy a barrel right now. Any help you can provide would be appreciated. Thanks again.

[niemi24s]

The barrel positioning tool is described in the Schuemann barrel fitting instructions thusly: ". . .wrap tape around a long steel rod with a diameter slightly smaller than the bore of the barrel. The tape is to avoid scratching the bore with the rod."

I just use a wooden dowel with a diameter slightly smaller than the bore.

[Semi-manual]

niemi24s: Thanks; I kind of figured it was going to be something like that. One more question and I'll stop (try to stop) being a pest. Why can't the relationship of the lower lug to the frame stop surface be checked without the barrel being in the slide? With the link in place and and the slide stop pin engaged, it is really easy to "see" if the lugs reach the frame. Also, you can physically detect any rearward motion and resistance by trying to turn the SS when pressing the barrel rearward. If you can get the pin in and out of the link while pushing back on the barrel, then the lugs must be against the frame. Am I over-simplifying things?

[log man]

niemi24s: Thanks; I kind of figured it was going to be something like that. One more question and I'll stop (try to stop) being a pest. Why can't the relationship of the lower lug to the frame stop surface be checked without the barrel being in the slide? With the link in place and and the slide stop pin engaged, it is really easy to "see" if the lugs reach the frame. Also, you can physically detect any rearward motion and resistance by trying to turn the SS when pressing the barrel rearward. If you can get the pin in and out of the link while pushing back on the barrel, then the lugs must be against the frame. Am I over-simplifying things?

No, you're right on. And this should be checked with the barrel in the slide. Checking without the slide will give you an idea of bottom of barrel to bed at link down clearance as you can see that clearance. And there are other ways of checking this.

A word about the link. The sole purpose of the link (if accuracy is a goal) is to pull the barrel down out of upper lug engagement before the lower lug hits the VIS. It must be loose enough so that in battery it doesn't contact the pin on the top or hinder it from going fully into battery. Nor should it hold the pin away from the lower lug cam surface. In other words the only time the link should bear any pressure on the pin is at link-down. Bar-Sto actually mills the hole into an oval to make sure the lower feet sit on the pin in battery.

LOG

[Dave Berryhill]

...A word about the link. The sole purpose of the link (if accuracy is a goal) is to pull the barrel down out of upper lug engagement before the lower lug hits the VIS. It must be loose enough so that in battery it doesn't contact the pin on the top or hinder it from going fully into battery. Nor should it hold the pin away from the lower lug cam surface. In other words the only time the link should bear any pressure on the pin is at link-down. Bar-Sto actually mills the hole into an oval to make sure the lower feet sit on the pin in battery.

LOG

Evidently most of the companies that make 1911s didn't get that memo! :D

Of course you are correct for an accurate, optimally functioning 1911.

[niemi24s]

Why can't the relationship of the lower lug to the frame stop surface be checked without the barrel being in the slide?Not sure if I fully understand the question, but maybe this'll help us understand each other.

The primary purpose of the tool in the barrel is to put the link in tension with the lower standing lugs against the VIS. This is the condition the barrel will be in during the linkdown sequence just as the barrel hits the VIS and the VIS halts the barrel's aftward motion. It is absolutely imperative that the radial locking lugs of the slide and barrel be fully disengaged (vertically) at this time because if they're not, the barrel (no longer going aftward) will try to stop the slide from going aftward. If this occurs, the lugs will "crash" and be damaged.

It is also absolutely imperative that barrel make its first contact with the frame at the VIS - not the bed. The only two things the barrel can contact in the frame are the VIS and the bed. If the barrel makes first contact with the bed its downward motion will be halted but this contact will not relieve the tension in link. Its aftward motion (remember, the back of the barrel is moving back and down in an arc because of the link) will be stopped at the same instant by the link. This will eventually break the link.

If you try to check for all this without the slide and just the barrel linked to the frame, there's no slide & bushing to support the front of the barrel and orient it properly with respect to the frame. This is because the back of the barrel slopes up almost 1° in battery and is essentially at 0° when fully linked down. When first contact is made with the VIS, the barrel's somewhere in between those two angles. In addition, with no slide the clearance between the top of the barrel and its bore in the slide can't be checked.

When the barrel makes first contact with the VIS it is not yet fully linked down. VIS contact immediately relieves the tension in the link and then the barrel's downward inertia and gravity cause its aft end to either fall to the bed or fall until the link goes into compression.

Schuemann calls for the link to halt the barrel 0.005" above the bed by going into compression. I, personally, see nothing wrong with the barrel falling all the way to the bed with the link loose (not in compression or tension).

Anyway, is the answer to your question somewhere in that - or in what Log Man posted?

[log man]

Schuemann calls for the link to halt the barrel 0.005" above the bed by going into compression. I, personally, see nothing wrong with the barrel falling all the way to the bed with the link loose (not in compression or tension).

Anyway, is the answer to your question somewhere in that - or in what Log Man posted?
Niemi, Schuemann does not say that and it is impossible for a barrel link combination that allows the lower lug to ride the slide stop pin to ever put the link in actual compression. As the lug side of the hole is always just below the lug cam surface. That can only occur when the barrel rides the link to begin with. When however you push the barrel back by the muzzle and the lower lug hits the VIS the link is in extension as it has just pulled the barrel down from the engagement with the upper lugs in the slide, at that position optimally there would be .005" between the barrel and bed.

LOG

[Semi-manual]

niemi24s (and Log Man): I think I finally have the whole picture. Thanks again.

[niemi24s]

Niemi, Schuemann does not say that . . . This from the Schuemann Timing Test Kit instractions on his website (our Tech Issues section), Test 3, paragraph 2, no test kit spring installed: "If the gun passes this test there is a minimum of 0.005 inch between the bottom of the barrel, in it's fully linked down position, and the top of the frame and the inside of the slide". [the underscore is mine] I think the "top of the frame" has got to be what's also known as the "barrel bed".

These instructions go on to say remove material from either the inside of the slide or the top of the frame until the gun passes Test 3. Test 3 concludes with "The rearward motion of the barrel will have been stopped by the barrel's lower lugs hitting the frame impact surface and the downward motion will have been stopped by the link in compression". [the underscore is mine]

Putting that all together means, to me at least, Schuemann wants his barrel stopped 0.005 inch above the bed by the link in compression when the Timing Test Kit instructions are followed. I find it odd that in the barrel fitting instructions you sent me there's no mention of this, except in a roundabout way when it says follow the Timing Test kit instruction - if you have them!

. . .and it is impossible for a barrel link combination that allows the lower lug to ride the slide stop pin to ever put the link in actual compression. As the lug side of the hole is always just below the lug cam surface. That can only occur when the barrel rides the link to begin with. It's possible if the lug side of the hole is exposed above the lug when the barrel's linked down. Kinda like a "partial link rider" - ride the link initially, then the lugs take over by obscuring a bit of the pin hole and then support the barrel in battery.When however you push the barrel back by the muzzle and the lower lug hits the VIS the link is in extension as it has just pulled the barrel down from the engagement with the upper lugs in the slide, at that position optimally there would be .005" between the barrel and bed.That makes good sense, giving plenty of assurance the barrel can never hit the bed first and break the link.

Seems we had the same sort of discussion a few months ago and I was going to contact Schuemann to see if the Timing Test Kit instructions posted on his website were outdated. Never did. Maybe I should.

Cheers

[niemi24s]

FWIW, I tried ordering a Schuemann timing test kit from them (just to get the written instructions to compare with that's on their website, http://schuemann.com/ ) and was told they ran out of the kits last year and do not plan to make up any more of them.

The person I talked to did say the website instructions were up to date, however. I'd sure like to verify that, so . . .

. . . If anybody has a Schuemann Timing Test Kit instruction sheet I'd much appreciate a copy of it. Just PM me and I'll respond with my mailing address.

Cheers & Thanx In Advance

[Semi-manual]

niemi24s The instructions I downloaded off the web still talk about using the "spring" so they can't be up to date as the spring has been replace by the "steel rod wrapped in tape" per what you have stated above.

[niemi24s]

Yeah, it is a little confusing.

The spring was part of the Timing Test Kit (no barrel included). The tape-wrapped steel rod is mentioned as a substitute for the spring in the fitting instructions that come with the barrel (no timing test kit included).

Clear as mud?

Cheers