Model 57 Yoke Endshake - Shims or Peening to fix?

[UnderDawgAl]

All: Been a long while since I last posted. Awhile back, I bought a Model 57-no dash that had obviously been shot a lot. It has both yoke-to-frame endshake and cylinder-to-yoke endshake.

Going through my Kuhnhausen book, I see that he recommends peening the yoke button if more than 1-2 shims are needed to remove the endshake such that the flange on the yoke barrel rides lightly but snugly up against the frame. Doing that, I would then have to file the inside of the yoke button a bit so that the yoke screw can fit.

Well, I just added a 0.002" shim, but the endshake was still there. Added another, still loose. Added a third, still loose. Finally, with five shims added--that's 0.010"--the yoke closes like it should, and there's no fore-and-aft play in the yoke. Of course, now the yoke screw won't go in all the way. The question here is whether I should just lightly file the yoke screw to fit so that no binding occurs on the button, or whether I should attempt to do the peening that he suggests.

Correct my logic here. If I remove the shims, wouldn't I need to peen the yoke button to move the metal back close to a full 0.010"? What I can't reconcile in my mind is how peening the button reduces the forward and backward motion of the entire stud. Can you help me understand that?

 

[armorer951]

To fit the yoke properly, the yoke button at the end of the stem will have to be fit to the screw.....not the other way around.
If you look on the front facing flat part of the button itself you should see a wear pattern from the pilot (unthreaded tip) of the yoke screw. The wear pattern looks like an arc on the smooth surface of the button. You may need a magnifier to see this contact arc. The button will need to be peened on the back side (outside) of the button just opposite where this mark terminates.

You can use a small 4 ounce hammer to lightly strike the button, and move the button canopy forward. This moves the contact surface of the button toward the screw pilot (the unthreaded portion at the end of the yoke screw), and closes the gauge or opening between the yoke button and this screw pilot. Carefully strike the outside of the button (not the side) at the place indicated, then insert the yoke only into the frame and try the fit on the screw. Keep lightly peening until the gauge is closed and there is no movement of the yoke forward when it is in position (closed in the frame) and the yoke screw is fully tightened. (remember to try a different screw first to see if that will remedy w/o peening)

There should be slight contact between the yoke screw pilot and the yoke button throughout the opening/closing movement of the yoke itself. The open gauge or end shake you are feeling on the yoke is due to wear and peening at the point on the button where the yoke is fully closed in the frame. If this peening is not severe, you can sometimes substitute a new or different yoke screw to fix the issue. Many people find that the middle screw in the sideplate....the one just above the rear of the trigger guard... will work to close the end shake. Try switching the screws prior to doing any peening on the yoke button.

Remember also that shims on the yoke stem will remedy the open gauge between the button and the yoke screw, but will move the yoke itself forward, and thereby, also allow the cylinder assy to move forward. As a result, the resulting inevitable end shake on the yoke barrel will also have to be remedied by shimming or stretching. Proper fitment of the yoke screw and the yoke button is the best remedy for the problem you describe, because the yoke is restored to it's proper position in the frame (fully to the rear) without shims.....and without causing end shake on the cylinder.

 

[WR Moore]

Going through my Kuhnhausen book, I see that he recommends peening the yoke button if more than 1-2 shims are needed to remove the endshake such that the flange on the yoke barrel rides lightly but snugly up against the frame. Doing that, I would then have to file the inside of the yoke button a bit so that the yoke screw can fit.

OK, Power Custom (now Grandmasters LLC) used to/may still make shims to fit the frame stud on the yoke to move the flange on the yoke barrel into contact with the frame. I believe the reference is to end play between yoke and frame, not the cylinder end play. The S&Ws I can quickly check seem to have a close fit between the yoke barrel flange and the frame.

I'll defer to armorer951 on the details of fitting the yoke/cylinder. My own view of the shim/stretch question is that the action of stretching the yoke barrel reduces the cross section of the yoke barrel. This makes the yoke weaker in the long term and may require replacement in the future. Shims, on the other hand, can be replaced as required without affecting the yoke integrity.

 

[UnderDawgAl]

Thanks, armorer951 for your instruction, pics, and comments. I'll plan this weekend to inspect the yoke button closely under magnification to see if I see that arc. Your pictures are extremely helpful.

Thanks, too, WR Moore, for your comments. I indeed already have the shims on hand for the yoke stud. Regarding your reference to the other type of endshake--yoke-to-cylinder--I agree completely that using the shims are preferable to stretching the yoke barrel, and I have successfully used them on an old K-38 which has since seen thousands of rounds of use.

 

[dannyabear]

During the 70s and 80s I owned and shot a 4" 57 and a 6" 57; Both had to be returned to S&W for new frames because the top strap strechs

 

[UnderDawgAl]

Thanks, guys, for your comments and suggestions. In particular, thanks to armorer951 for the excellent pictures and descriptions, which I've studied closely.

The reality of lack of time and multiple other priorities being higher led me to contact S&W about repairing it. They sent me a prepaid shipping label a week ago, so I shipped it last weekend. They received it this past Tuesday morning, October 23. We'll see what they come back with, how long it takes, and how much it costs.