Yoke button wear/endshake, how should I fix it?

[sza]

This is the yoke button on my model 19-2:

The gun has obviously seen some use. It has a noticable amount of yoke endshake.

Kunhausen mentions a few different ways to fix yoke endshake.

1. Installation of a .002" yoke bearing
2. Installation of a "#2 Endshake Screw"
3. Peening the yoke button, then fitting it to a standard endshake screw
4. Various combinations of the above

What are the pros and cons of the various repair methods?

I have yoke and cylinder endshake bearings on hand, so it'd be fairly simple to try a yoke bearing. I assume I'd also want to stone or lightly file the rough edges off the worn area of the yoke if I go this direction.

How much larger in diameter is the "#2 Endshake Screw", and where can I get one?

Peening the yoke button seems like it'd be the method I'd be most likely to screw up, but it also seems like the method that would have the best longevity as after peening the button down and squaring off the inside of the slot there'd be a completely flat surface for the endshake screw to bear against.

Thanks in advance for any advice.

 

[tomcatt51]

There are two seperate issues. You use the shims so there is virtually no you endplay/endshake with the yoke closed and the screw out. Then you peen/fit the button so the yoke doesn't have endplay/endshake when open. If you If you just peen the yoke and set the closed yoke endplay without shimming the yoke forward against the frame first, the screw will just wear into the yoke button again increasing endply/endshake until the yoke does sit forward against the frame.

The wear on your yoke looks like maybe the "wrong" screw was in that position.

 

[Jerry in SC]

Yep, someone switched screws it appears.

Peening is not rocket science; you need a lead babbit bar and a 4 ounce hammer. The #1 or #2 Barrette file makes the fitting job easier. Go slow and light.

S&W no longer offers the #2 endshake screw according to the parts dept.

 

[sza]

There are two seperate issues. You use the shims so there is virtually no you endplay/endshake with the yoke closed and the screw out. Then you peen/fit the button so the yoke doesn't have endplay/endshake when open. If you If you just peen the yoke and set the closed yoke endplay without shimming the yoke forward against the frame first, the screw will just wear into the yoke button again increasing endply/endshake until the yoke does sit forward against the frame.

I'm not sure I fully understand this.

The yoke shims would move the yoke forward, correct? What part of the frame should the yoke be in (near) contact with when closed? The barrel lug? Or is there something else I'm not getting?

I'm at work so I don't have the gun handy to look, it'll probably be obvious once I get home and look at it.

 

[tomcatt51]

Should be obvious with the gun in hand. There's a thrust surface on the yoke (around the yoke barrel) that rests against the frame limiting the yoke's forward travel. In a perfect world the yoke is snug sgainst that surface, zero yoke endshake/endplay, without shims, with the yoke closed and the yoke screw not installed.

 

[sza]

You're right, it was obvious with the gun in hand, and I understand now.

However, I've got even more questions now!

If the endshake with the cylinder closed is controlled by the thrust surface on the yoke and its contact with the frame, why does the yoke endshake with the cylinder open matter?

If the yoke screw doesn't bear any load with the cylinder closed and the yoke endshake with the cylinder open doesn't matter, why peen the yoke button for a tight fit on the yoke screw? Is the purpose just to keep the thrust surface on the yoke from crashing into the frame when you close it? (Presumably accelerating the wear on the contact points that control cylinder closed endshake)

Thanks again for all your help!

 

[tomcatt51]

If the endshake with the cylinder closed is controlled by the thrust surface on the yoke and its contact with the frame, why does the yoke endshake with the cylinder open matter?

So the cylinder will close nicely with the surfaces sliding past each other instead of the surface's edges bashing each other.

 

[sza]

Got it, thanks! I'm going to order the correct file and a babbitt bar soon, then I'll attempt to tackle this repair.