I looked through Jerry K's shop manual but could not find anything on fitting the front side plate screw, except don't get it mixed up with the other screws. Any advice?
Fitting Yoke Screw Question.
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Alk8944
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Usually the only thing to fitting the yoke screw is shortening it just a few thousandths of an inch, .005" or even less, so when it is tightened the end of the screw doesn't bind in the bottom of the groove in the yoke. Simply use a fine cut flat file to shorten the screw, being careful to keep the end of the screw squared to the body. Just cut and try the screw until it doesn't cause the yoke to be difficult to move when tightened.
This assumes you have a gun with the solid yoke screw. The later one with a spring-loaded plunger doesn't need fitting. It is also larger than the other side plate screws and isn't interchangeable anyway.
This assumes you have a gun with the solid yoke screw. The later one with a spring-loaded plunger doesn't need fitting. It is also larger than the other side plate screws and isn't interchangeable anyway.
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Prior to the new yoke retention revision in 1988, the yoke was retained by the interface between the piloted front sideplate screw, and what is described by the factory as a "button" at the end of the yoke frame stem. (see image below)
Initial fitting of the "back" side of the yoke button was performed during fitting by techs at the factory during the construction of the revolver. This interface, between the pilot, or unthreaded stem at the end of the yoke screw, and the yoke button, holds the yoke and attached cylinder assembly in place on the frame, and at the same time, allows the assembly to be rotated approximately 90° on the yoke stem axis. The unthreaded side of the yoke screw is what interacts with the button of the yoke, not the end of the screw.
Initial fitting at the factory involved removal of material from the front facing bearing surface of the yoke button, which directly interfaces with the side of the piloted stem of the yoke screw.
Ideally, correct fitting established direct contact between the screw pilot and the button of the yoke when the cylinder was in the closed position, and during the opening and closing of the cylinder. This fit both eliminates end shake on the yoke, and permits the unhindered opening and closing of the cylinder assembly by the user. The contact "arc" showing constant contact between the yoke button and the side of the unthreaded portion of the piloted screw can be seen in the image below.
The yoke retention revision eliminated this fitting requirement by utilizing a screw that incorporates a spring and plunger (at left in the attached image) that interfaces with a "V" shaped cutaway in the frame stem of the yoke.
As you can imagine, fitting and repair of this interface was both tedious and time consuming, and involved considerable experience, skill, and familiarity with the barrette file, and with peening.
New vs old yoke screw retention/revision:
Yoke button contact by yoke screw pilot:
In the event the yoke button/yoke screw interface required refitting due to wear or damage, armorers would first attempt using a new screw to resolve end shake on the yoke. If the new screw (or oversize screw) would not resolve the issue, the yoke button could be "peened" at the "closed" position, which would restore proper contact between the side of the yoke screw pilot and the front side of the button, thus eliminating excess gauge at the interface. (end shake on the yoke)
Some limited yoke/frame fit information is provided on pages 46, 47, 48, 49 in the 5th Edition Shop Manual by Jerry Kuhnhausen.
Carter
Initial fitting of the "back" side of the yoke button was performed during fitting by techs at the factory during the construction of the revolver. This interface, between the pilot, or unthreaded stem at the end of the yoke screw, and the yoke button, holds the yoke and attached cylinder assembly in place on the frame, and at the same time, allows the assembly to be rotated approximately 90° on the yoke stem axis. The unthreaded side of the yoke screw is what interacts with the button of the yoke, not the end of the screw.
Initial fitting at the factory involved removal of material from the front facing bearing surface of the yoke button, which directly interfaces with the side of the piloted stem of the yoke screw.
Ideally, correct fitting established direct contact between the screw pilot and the button of the yoke when the cylinder was in the closed position, and during the opening and closing of the cylinder. This fit both eliminates end shake on the yoke, and permits the unhindered opening and closing of the cylinder assembly by the user. The contact "arc" showing constant contact between the yoke button and the side of the unthreaded portion of the piloted screw can be seen in the image below.
The yoke retention revision eliminated this fitting requirement by utilizing a screw that incorporates a spring and plunger (at left in the attached image) that interfaces with a "V" shaped cutaway in the frame stem of the yoke.
As you can imagine, fitting and repair of this interface was both tedious and time consuming, and involved considerable experience, skill, and familiarity with the barrette file, and with peening.
New vs old yoke screw retention/revision:
Yoke button contact by yoke screw pilot:
In the event the yoke button/yoke screw interface required refitting due to wear or damage, armorers would first attempt using a new screw to resolve end shake on the yoke. If the new screw (or oversize screw) would not resolve the issue, the yoke button could be "peened" at the "closed" position, which would restore proper contact between the side of the yoke screw pilot and the front side of the button, thus eliminating excess gauge at the interface. (end shake on the yoke)
Some limited yoke/frame fit information is provided on pages 46, 47, 48, 49 in the 5th Edition Shop Manual by Jerry Kuhnhausen.
Carter
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Great info, Carter.
OP
Thanks Carter. I'll let you know how it goes. I must have an older edition of Jerry's shop manual.
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Carter,
I won't argue with what you say for modern times, but guns from the 50s back show filing on the screw pilot. They sometimes show some light filing on the button, probably because the screw had gouged it when they first ran it in.
So, I run the new screw in tight and use a pencil to mark 9 o'clock where the screw is against the button. Take it out and examine yoke. If the screw raised a burr on the button, stone or file it off. Try screw again. If still tight, make sure the mark at 9 is still there, remove screw and file the pilot lightly at 9 o'clock. Go slow, try often.
I won't argue with what you say for modern times, but guns from the 50s back show filing on the screw pilot. They sometimes show some light filing on the button, probably because the screw had gouged it when they first ran it in.
So, I run the new screw in tight and use a pencil to mark 9 o'clock where the screw is against the button. Take it out and examine yoke. If the screw raised a burr on the button, stone or file it off. Try screw again. If still tight, make sure the mark at 9 is still there, remove screw and file the pilot lightly at 9 o'clock. Go slow, try often.
OP
I understand why S&W went to the three piece device to replace the old screw. The trigger guard screw was another one that was a pain.
A while ago I sent a 29-2 to the factory to replace the red insert on the front sight. The guy that did the work at the Performance Center also replaced the side plate screws and sent the old ones back with the gun. I just pulled those screws, which were like new, and one of them dropped right in. The yoke is perfect and the cylinder swings just right. I lucked out on that. My new (to me) 57 of the same vintage works perfectly now. Yep, lucked out again.
A while ago I sent a 29-2 to the factory to replace the red insert on the front sight. The guy that did the work at the Performance Center also replaced the side plate screws and sent the old ones back with the gun. I just pulled those screws, which were like new, and one of them dropped right in. The yoke is perfect and the cylinder swings just right. I lucked out on that. My new (to me) 57 of the same vintage works perfectly now. Yep, lucked out again.
Sometimes, if things "go the right way," one can eliminate a bit of yoke shake just by selecting a new screw. In my little assortment of screws I see variation in the "pilot" diameter of the screw by .007-.008". (Translates to half of that in actual range of adjustment.) Very much appreciate Carter's contribution. I have a problem child 29-2 that needs its yoke button peened, but I am too cowardly to try it and have adjusted the gun with shims. Not ideal, to be sure, but at least no permanent harm is done.
