Endshake on 29-2

[deuterij]

I have an old model 29-2 purchased months ago from another forum member. It is a beautiful gun, but has a bit more endshake than I am used to seeing. After reading Magnum 500 Nut's FAQ thread, I measured the endshake (in other machines I've heard this type of measurement referred to as axial endplay) using a metal feeler gauge. I hope this feeler gauge was OK to use because I did not want to damage the gun (are plastic thickness gauges available?).

I measured 0.002" with cylinder pushed forward, 0.008" with cylinder pushed back. It is a difficult measurement to make because it seems like the breech face of the barrel (the flat adjacent to the front of the cylinder) was factory-trimmed using a large diameter grinding wheel, so it does not have a perfectly flat surface. So the feeler gauge slides part way in, then hangs up on raised portion of the breech face. Anyway I sort of took the average reading when the feeler blade slid most of the way in with light resistance.

Anyway, is 0.006" of cylinder endplay excessive? I read that the standard is 0.002" I can picture the cylinder/ratchet moving backwards under firing pressure and hammering against the recoil plate, possibly peening the surfaces and leading to larger endplay. I would be shooting 44 Specials, not Magnums in this gun.

I want to take it to range soon but wanted the opinions of some forum members first. If the consensus it that this endshake is excessive, I will undertake the endshake repair posted in Magnum 500 Nut's FAQ.

Thanks,

-E

 

[bgrafsr]

I believe that .010 thousandths is acceptable by S&W standards, so you are okay. If it was mine however, I would either stretch the yoke or install an endshake bearing to open the barrel/cylinder gap to about .004 to .006 thousandths.

 

[dfariswheel]

0.006" is RIGHT on the edge of what's permissible in the S&W.
I'd be looking at a repair before shooting too much more.

 

[bountyhunter]

I believe that .010 thousandths is acceptable by S&W standards, so you are okay.

According to Kuhnhausen, .010" is acceptable for barrel cylinder gap, certainly not for end shake. The official spec on end shake is .000 - .001", which is why the end shake washers are .002" thick: when the end shake is .002", you put in a washer.

.006" end shake is bad, I would fix before shooting.

 

[deuterij]

Thanks so far. In wiping down the gun since originally posting, I noticed something else. When I push in on the yoke, it moves a bit. The cylinder bolt spring normally pushes the cylinder forward, towards the barrel breech. On mine it seems to push the entire yoke forward too. I think most of that 0.006" play I am feeling is because the entire yoke/cylinder assembly is moving.

I remember reading somewhere about tightening up the yoke. Tomorrow I will try removing that yoke-retaining sideplate screw and pulling out the yoke. I am thinking that the only thing holding the yoke against forward motion is that retaining screw. If I can reduce the gap there, maybe I can cure the endplay.

 

[500 Magnum Nut]

Try switching the bottom 2 screws. If that won't do it. I have the method in the faq. It's easy to do.

Endshake over .003 is bad and should be corrected asap. The larger the shake, the faster it grows.

 

[bountyhunter]

Thanks so far. In wiping down the gun since originally posting, I noticed something else. When I push in on the yoke, it moves a bit. The cylinder bolt spring normally pushes the cylinder forward, towards the barrel breech. On mine it seems to push the entire yoke forward too. I think most of that 0.006" play I am feeling is because the entire yoke/cylinder assembly is moving.

I remember reading somewhere about tightening up the yoke. Tomorrow I will try removing that yoke-retaining sideplate screw and pulling out the yoke. I am thinking that the only thing holding the yoke against forward motion is that retaining screw. If I can reduce the gap there, maybe I can cure the endplay.

Notice there are actually two parts to what is normally called "endshake" (cylinder fore aft movement) and one is the yokes play which in most guns is negligible.

To get the true endshake, you measure the yoke end play, then mesaure the total cylinder end play. The cylinder endshake is the difference. If your yoke has a lot of play, fix that first then remeasure end shake.

 

[deuterij]

I gotcha. It seems I have the yoke play problem. I will try the screw swapping method, then the yoke shaft button peening method.

Thanks all.

 

[S&W revolverman]

Endshake problems

I've stated this before and I'll state it again. And, I feel strongly for this.

BEFORE, you do ANY work to your S&W revolver, make sure it is positively clean - inside and out. There are tolerance differences with each older gun. Hand fit or not, it is just a fact of life. So, you need know how to dissamble the revolver. Then, if the problem you think is still aparent, then work on that.

I read guys that state : I have end shake, I have blow by, I have shaved lead, etc. Clean your revolver inside and out thoroughly. I mean take the internals apart piece by piece and cleaning them. Then go with the problem as stated. Otherwise , you maybe chasing the problem, instead of fixing it.

Hope this helps
chris

 

[tomcatt51]

I gotcha. It seems I have the yoke play problem. I will try the screw swapping method, then the yoke shaft button peening method.

Thanks all.

I've always questioned the wisdom of doing the button peen vs shimming the yoke. There is a thrust surface on the yoke that should be in contact with the frame when the cylinder is closed. The yoke screw holds the cylinder back so it will open and close properly. On older guns if the screw/yoke button are fitted to control yoke endplay instead of the frame/yoke being in contact, the screw peens into the button until the suraces do contact. The screw/button is a lousy thrust surface compared to the frame/yoke surfaces.

Shimming the yoke/frame endplay seems like the way to go from a mechanical standpoint. When you take out the yoke endplay by the button peening method you pull the yoke back out of contact with the frame/yoke thrust surface and the screw/button absorbs the thrust and the screw beats a dinger in the button and your cylinder opens funny and your yoke endplay (and cylinder endplay/endshake) is back.

I can see where cosmetically the button peen may be more desireable because the yoke/frame will be aligned in the position it was finished in and for a fairly low round count gun it will stay adjusted for a while. For high round count and heavy recoiling guns the shims seem to hold things in tolerance better.

If you shim the yoke you will need to adjust your cylinder endshake because the shims move the yoke forward increasing cylinder endshake/endplay. Just my 2 cents.

 

[ViperR]

I agree with tomcatt51. All the yoke/side plate screw is for is to keep the yoke/cyl assembly from falling out when you open the cylinder. it is not to hold the yoke when the cyl is closed. The frame is for that and as said above, you start by shimming the yoke, then correct the end shake. Power Custom sells shims for both yoke & end shake.
BTW, you might have to re-fit the yoke screw after adding a yoke shim. I believe PC makes shims very thin (which is needed), compared to end shake shims. You would also be smart to ream the inside of the cyl flush of the peening groove that has been created.

 

[500 Magnum Nut]

If the button is peened, the yoke is pulled tighter to the frame. It looks nice, no extra slop and the shims are not needed.

That's why you can try the swapping the screw trick, as sometimes the screw gets dinged up or gets rubbed down.

 

[S&W revolverman]

That's why you can try the swapping the screw trick, as sometimes the screw gets dinged up or gets rubbed down.

I don't believe the yoke screw gets dinged up or rubbed down, it is the button of the yoke which may be softer then the yoke screw that wears. The yoke screw may be fitted too tightly in the beginning, then in wears into the button of the yoke which is perfect, then gets too much wear over time with shooting with the yoke bouncing back and forth with shooting. Especially with magnum loads, and not so much with target loads.

I always fit the yoke screw a liitle tight in the beginning, which makes the cylinder only a tad bit hard to open, but the yoke screw will wear in to the yoke button easily, then a perfect fit.
Always a drop of oil helps at this juncture too.

But, now, I am in agreement with swapping the original yoke srew with the other sideplate screw if there is a yoke end shake problem. Just because the other sideplate screw might be a little bit longer so as to fit more properly. Or, to make fit more properly. If this swapping does not work OK, then an oversized yoke screw may be necesssary, notwithstanding, the peening of the yoke, etc.
Now, all of this does not apply to newer yoke screws which are spring loaded. I really haven't see any yoke endshake problems with these newer spring loaded screws. If there is a yoke endshake problem with a newer revolver. Then, then the fix for this is just to install a new spring loaded yoke screw.

Hope this helps
chris

 

[deuterij]

What I did

Thanks everybody for the helpful comments. I finally got around to working on this 29-2 with yoke shake, What I ended up doing was fashioning a tiny shim washer out of 0.005" thick brass. I had to skive cut it to get it around the reduced diameter portion of the yoke shaft. I was careful to see that it rested in the correct position by peering into the sideplate screw hole, then I put in the screw. I felt slight resistance as the screw reached bottom. Also the yoke gets tight as it swings out (which makes sense given the below-described filing that somebody did), but overall it feels better. I am now measuring b/c gap of 0.008" with cylinder back and 0.005" with cylinder forward. This means 0.003" of endplay which I think I can live with.

I had first tried peening the yoke button but it did not feel right and it started looking like the entire button was bending over rather than peening down. It also appeared that somebody had filed the inside edge of the button where the sideplate screw would normally touch, perhaps in an attempt to eliminate interference. They had removed too much material so that the groove width went from 0.110" at its bottom to 0.120" near the edge. I would have had to peen the heck out of it get that 0.010" back. I guess that this groove might be factory cut with a bit of angle on its sides, in order to get adjustability with varying sideplate screw length, but the obvious filing had greatly increased this angle in one region of the circumference.

I had also tried swapping the 2 sideplate screws but that had no effect. I remember reading once that swapping sideplate screws is a no-no, because they are fitted screws. Is this not true?

Regarding the frame acting as a forward yoke stop with the cylinder closed, I do not see that happening on my gun. No part of my frame seemed to stop the yoke's forward motion. There is a bit of the barrel lug that sits in front of the yoke, but there was plenty of air gap there when I sighted on it with backlight, even with the yoke pushed fully forward. I cannot imagine much forward loading on the cylinder during firing, only rearward loading caused by high pressure at the barrel/cylinder area.

 

[ViperR]

Both my revolvers rely on the lower barrel lug as a locking possition for the yoke. You want that and that is what a yoke shim does. I positions the yoke more forward to mate up with the lug for an exact fit. Then you tackle endshake via the cylinder yoke tube area.
I have thinner brass & steel stock (I mean real thin) and I can mail you some if your .005" is too thick. Shoot me a PM.

 

[deuterij]

Well it seems Tomcatt51 and ViperR had some insight. My fix failed after a visit to the range. After about 75 of 44 Special rounds, the endshake was back.

Upon closer inspection, I did see a tiny bearing surface on the frame. It goes about 1/4 of the way around, just forward of the gas ring area. The next thing I will try is the regular endshake shims. It seems that will push the yoke forward so it stands a bit proud of the frame, but I'd rather fix the endshake.

In trying to peen yoke buttons on 2 different guns, I noticed that a tiny divot forms in the groove, just where the screw tip would contact it with the cylinder closed. This makes it difficult to keep the yoke's axial play down.

Thanks again for helpful comments. This has been a learning experience for me.