S&W crane endshake

[Daizee]

I recently noticed a little bit of endshake in my Model-10.
Unlikely that it's the result of a box of too-hot handloads, but I didn't notice it 'til last week.

The movement is small. I'd estimate 0.001 (no feeler gauges), but irritating. The crane moves forward and back in its channel.Is there anything to to be done about it short of sending it to S&W, whom I assume will say that it's in-spec? Does one replace the crane? Isn't that a hand-fit part? Are there standard shims? A fatter cylinder retention screw?

The lockup looks fine otherwise, and the crane does not appear to be bent.
I intend to shoot this gun a lot in IDPA club matches, and I can feel the *clack* of the endshake when re-holstering as the leather grabs the cylinder.

I love this gun, and want it to live forever like it should. :-(

Thanks for any advice.

-Daizee

 

[Sylvan-Forge]

According to "The S&W Revolver - A Shop Manual" by Jerry Kuhnhausen, a quick repair for closed-yoke endshake can be made by replacing the yoke screw with a larger #2 yoke retaining screw. He advises an alternative "better way" is to install yoke bearing washer(s) which can be had in 0.002" thickness and are to be tested one at a time until yoke endshake/endplay is eliminated. He notes that these bearings should be kept lightly oiled.

.

 

[Daizee]

Excellent, thanks Sylvan!

Obviously I need this book.
He doesn't explain how one finds a "larger #2 yoke retaining screw", does he? Presumably it's written for a proper gunsmith shop which would have piles of parts around.

-Daizee

 

[machinisttx]

I have yet to see a #2 yoke screw offered by any parts supplier. I'm going to guess that they are only available to folks who have been through S&W's "armorer school".

You might try having a look at this thread that I wrote up on another forum. It's not perfect, but it should give you an idea of what needs to be done.

 

[Sylvan-Forge]

You're most welcome, Daizee.

Aye, it's a fine book. No, unfortunately I don't think he describes where to find those screws.

That's an excellent thread, machinisttx!
Gonna have to copy that.

EDIT:
Just called S&W and they have "oversized" yoke screws for blued k/l frames. No stainless.
I ordered up 3 for a rainy day.

.

 

[Daizee]

Machinist, that's a fantastic photo lesson. I had no idea that the .002 shims went *inside* the cylinder. You have removed a lot of mystery.

Can you solve late carry-up by peening out the hand in the same way? (obviously this would adjust it for all chambers, and fortunately my gun doesn't have this problem)

-Daizee

 

[Daizee]

Sylvan, can you mic the end of those screws when they arrive? I'd like to compare the retaining area diameter to my current screw. I'll probably check tonight with the screw and yoke off the gun to see if the fit is sloppy.

I think I'd like to try a reversible fix like that before I try peening the yoke. No lead bar here to use yet.

-Daizee

 

[Sylvan-Forge]

Sure Daizee, though I don't have a mic. I should be able to get a working measurement with a dial caliper.

The crane moves forward and back in its channel.

The bearings I was referring to go on the Yoke Stud, not in the cylinder.
They bear against the yoke body and the frame.

I'll write a more detailed descript later t'night if possible.

.

 

[earplug]

I was taught at my gunsmithing class to fix a loose crane by lightly tapping the crane with a hammer. You place the forward part of the crane on a babbit bar, or ingot of lead, and strike the rear most area of the crane where the screw engages. This will pean/tighten the screw slot up. Go slow and easy or you will have to remove metal to get the screw to fit.
Look at the relationship of the crane screw and the notch on the crane and you will find the best spot to strike with your hammer.

 

[Jim K]

If your revolver is one of the older ones that has the front sideplate screw (yoke retaining screw) and the lower sideplate screw identical, just try swapping screws.

Jim

 

[machinisttx]

Machinist, that's a fantastic photo lesson. I had no idea that the .002 shims went *inside* the cylinder. You have removed a lot of mystery.

Can you solve late carry-up by peening out the hand in the same way? (obviously this would adjust it for all chambers, and fortunately my gun doesn't have this problem)

-Daizee

Yes, the hand can be peened. Personally, I'd only do that as an absolute last resort or as a field expedient repair until I could find a proper replacement part.

ETA---The cylinder bearings come in two thicknesses, .002" and .004". I would use a .004" if endshake was truly excessive.

Thanks for the compliment.

 

[machinisttx]

EDIT:
Just called S&W and they have "oversized" yoke screws for blued k/l frames. No stainless.
I ordered up 3 for a rainy day.

Ooooo....I did not know this. I suppose I should order a few myself. Be aware that you will likely have to fit the screw slot in the yoke for proper function.

 

[machinisttx]

The bearings I was referring to go on the Yoke Stud, not in the cylinder.
They bear against the yoke body and the frame.

I'll write a more detailed descript later t'night if possible.

If you use a yoke bearing, you will have cylinder endshake afterwards. It's likely that you already have cylinder endshake, but you do need to fix the yoke endshake before addressing it.

 

[Daizee]

Ok, so this was instructive.

My gun is a 10-8 with identical (to my eye) front and bottom sideplate screws.
I swapped them and had the same endshake.
Then I took the calipers to them - identical.
So then I looked at the slot in the yoke where the screw tip retains it.

Aha! after a bunch of measuring and then some better light, I found a slight divot of about 0.004 in the retaining surface (rearmost) of the yoke, right where the screw contacts the cylinder when closed. Is this normal? It looks like someone (maybe me??) tightened the screw with the cylinder not all the way in (tho how would that be).

I should take a pic of this.
Peening the yoke won't work as I'd have to dent the thing way out of place to get the closed position to fit. Then the thing wouldn't open. Interestingly, the yoke opens smoothly and does NOT appear to exhibit any shake while open.

An oversize screw will cause the same problem as peening the crane (tho less destructively).
It seems a yoke replacement would be the best option, but I bet that's a fitting nightmare. A possible alternative might be to fill the divot with some thin filler like JBWeld and then smooth it out.

Is that a stupid idea?

-Daizee

 

[Sylvan-Forge]

Aye, a pic would be helpful

This divot you speak of, it is in the Yoke Screw Slot?
It does not appear to be normal wear, but damage from having tightened the yoke screw while the yoke was out of the frame just a tiny bit?

No shake when open. Hmm, when the yoke is closed and fired there would eventually be wear on the screw slot. When the yoke opened, the worn (or damaged) spot is rotated away from the yoke screw and the relatively unworn portion of the screw slot surface is now in contact, tightening the yoke, hence no discernable endshake when open.

Yoke endshake must be tested with the yoke closed.

Just to be clear, there is two basic kinds of endshake or endplay:
Yoke-to-Frame and Yoke-to-Cylinder.

Also to be clear, I'm no smith or machinist, I just got this here book

Here's a paint pic:

.

 

[Master Blaster]

The movement is small. I'd estimate 0.001 (no feeler gauges), but irritating

First you need gauges, Any gunsmith's ability to percisely measure 1/100 by guestimation is suspect let alone 1/1000. Its why gunsmiths use gauges. Kuhnhausen in his shop manual says that the design needs a tiny bit of end shake 1/1000 or so to work or you won't be able to close or open the cylinder easily, and will cause excessive wear.

Second other than your annoyance, is the gun exhibiting any symptoms of end shake? Like failure to carry up/timing, spitiing lead? cylinder hitting the barrel on a couple chambers???

If the answer to any of these questions is no, I would stop inspecting the gun and put another 20,000 or so rounds through it before you worry about endshake. You may just find it shoots very well, and continued attempts to fix a problem that doesn't exist may cause real damage to your gun.

JMHO YMMV

 

[Sylvan-Forge]

Indeed, a set of feeler gauges will be needed to accurately check cylinder endshake, barrel gap and headspace (rear gauge).

A small amount of yoke endshake isn't the end of the world but would accelerate wear. He did say he intends to shoot it a lot and wants it to live a long time.

JK (and machinisttx) says to eliminate yoke endshake before checking cylinder endshake.
The cylinder endshake should be ~0.001"

JK differentiates between fine endshake and gross endshake.

For fine yoke endshake: screw and/or bearing(s).

For gross yoke endshake: is endshake that cannot be corrected by 1 or 2 0.002" bearings and an oversized (#2) yoke screw.
Req: 45deg. peening yoke button, retrue slot to standard yoke screw, final fit+polish.

Note: regardless of fine or gross correction, one should ensure that the yoke flange swings into proper contact with the frame on closing. (Firm but light are the words used).

If yoke endshake is as small as he thinks it is (and there is no damage), the oversized screw and/or washer should be all that is needed to eliminate yoke endshake (as well as being easily reversed). A set of feeler gauges for other important measurements would certainly be prudent. A couple extra bearing washers for the cylinder in case of minor/fine cylinder endshake.

.

 

[1KPerDay]

What's the price I could expect to pay someone to correct yoke/cylinder endshake (where the barrel/cyl gap is too tight)?

 

[Steve C]

There is an allow and normal amount of end shake, can't remember the numbers right now but I'm sure that someone will post them. Don't fix what isn't broken.

 

[Sylvan-Forge]

I don't know what is considered allowable.
Optimum measurements according to JK, in order:

1. Closed Yoke Endshake: Eliminate. (as in 0 I reckon )
2. Verify yoke alignment, smooth operation and proper yoke-flange to frame contact.
3. Cylinder Endshake: 0.001".
4. Cylinder Gauge Check: Barrel-Cylinder Gap: 0.004 - 0.006" (I believe S&W says up to 0.009"). Verify barrel face is square to cylinder. Verify headspace (rear gauge).

.

I seem to recall reading somewhere of a setup using a 0.002 Barrel-Cylinder gap in conjunction with a specific forcing-cone angle-cut to be used with a certain type of bullet (lead?). I think it might have been Linebaugh Custom Sixguns.

.

 

[machinisttx]

There is an allow and normal amount of end shake, can't remember the numbers right now but I'm sure that someone will post them. Don't fix what isn't broken.

Yoke endshake is bad. Zero is the amount of movement that is acceptable.

Cylinder endshake is just about perfect at .001".

More endshake = more develops at a faster rate. The gun eventually beats itself to death if it isn't corrected.

 

[machinisttx]

Ok, so this was instructive.

My gun is a 10-8 with identical (to my eye) front and bottom sideplate screws.
I swapped them and had the same endshake.
Then I took the calipers to them - identical.
So then I looked at the slot in the yoke where the screw tip retains it.

Aha! after a bunch of measuring and then some better light, I found a slight divot of about 0.004 in the retaining surface (rearmost) of the yoke, right where the screw contacts the cylinder when closed. Is this normal? It looks like someone (maybe me??) tightened the screw with the cylinder not all the way in (tho how would that be).

I should take a pic of this.
Peening the yoke won't work as I'd have to dent the thing way out of place to get the closed position to fit. Then the thing wouldn't open. Interestingly, the yoke opens smoothly and does NOT appear to exhibit any shake while open.

An oversize screw will cause the same problem as peening the crane (tho less destructively).
It seems a yoke replacement would be the best option, but I bet that's a fitting nightmare. A possible alternative might be to fill the divot with some thin filler like JBWeld and then smooth it out.

Is that a stupid idea?

-Daizee

It actually doesn't take much peening to correct the divot. You'll have to refit the slot to the screw after doing so by filing---use swiss type needle files with a safe edge for this.

S&W will not sell you a yoke(they will fit a new one for you though). You MAY be able to find one through somewhere like Numrich---but your suspicion is correct, it would have to be fitted to the gun.

IMO, JB weld would be a bad idea...... If I were going to try to fill in such a divot, I'd use a tig welder....of course, that would require rebluing the yoke and then it probably wouldn't match the rest of the gun....

 

[machinisttx]

If yoke endshake is as small as he thinks it is (and there is no damage), the oversized screw and/or washer should be all that is needed to eliminate yoke endshake (as well as being easily reversed). A set of feeler gauges for other important measurements would certainly be prudent. A couple extra bearing washers for the cylinder in case of minor/fine cylinder endshake.

Arrr...

Installing a yoke bearing WILL create cylinder endshake. If yoke endshake is present, I would say it is likely that cylinder endshake is already present--so you'd only be adding to the problem.

Depending on the diameter of the bearing surface(the part that rides in the retention slot on the yoke) on the #2 screw, the bearing surface on the yoke button will likely require refitting as well. It might screw in just fine with the yoke closed, but then it would be impossible to open the gun with normal pressure--which would require filing the slot to obtain proper fit.

 

[Daizee]

Here's a picture.

The left-most arrow points to the divot, which I had thought was under the cylinder retention screw.

The right-most arrow points to what I thought would be the end of the contact area, given the wear in the bluing.



-Daizee

 

[Daizee]

new theory - plausible?:

I had an oops in a match a few weeks ago. Unburnt powder under the ejector star prevented the cylinder from closing. Unfamiliar with the problem, befuddled, and on the clock, I tried to close it pretty firmly (by hand!) a number of times. The cylinder hung up where the ratchets contacted the recoil shield. This *could* have peened the stop screw slot against the stop screw somewhere partly between the open and closed position, resulting in that divot. The screw itself might be peened forward a bit and not entirely straight at the tip, or flattened imperceptibly.

If this were the case I'd expect swapping the two frame screws to show some sort of difference, but it didn't. Maybe the screw itself is ok.

-Daizee