Yoke gap issue

[jmclfrsh]

I bought a 629 that needed some TLC, and I am providing it. It was a little “loose.”

Two .002 cylinder endshake shims really helped the fore-and-aft cylinder slop. Now it is nice, with a .008 cylinder/forcing cone gap - within spec, but a little bit larger than I would like - and the headspace is ok.

The cylinder has some cylinder stop slop, and I have an oversized cylinder stop I am going to have my gunsmith install. That should take care of that.

The remaining issue is the yoke can come away from the frame a slight amount, probably .002. I put in a lubricated .002 yoke shim, which forced the yoke ever-so-slightly against the ejector rod shroud and it helped a good bit.

I also installed a new cylinder pin and ejector rod, and my gunsmith installed a new cylinder ejector rod bolt, that spring-loaded jobbie the end of the cylinder rod goes around when the cylinder is closed.

What can I do to stop the yoke from having a little gap when the right side of the cylinder is pushed to the left? It is slight, but it and the cylinder stop slop is still bothering me.

I installed the new ejector rod and pin to make sure they were of the correct dimensions.

My other two N frames do not have this issue. How do I get rid of it?

 

[armorer951]

Fitting the cylinder assembly and yoke to the gun is a work that involves some compromise. Because of fitting issues, slight differences in the dimensions of the individual parts, and use or misuse after being put into service, revolvers will exhibit slight differences in terms of final fit, or "tightness" as some describe it. Admittedly, some of the issues with the yoke, including the "gap" and slight movement you describe, are purely cosmetic, and have no bearing on the integrity of the action at all.

Since the entire assembly must move in and out of the frame, and individual components must interface with each other with as little friction between the components as possible, it becomes necessary for there to be some gauge to enable the assembly to work as desired. Each revolver will be different or "unique" in this respect. This necessary gauge or "space" between interfacing parts can be removed, but only to the point where necessary movement is still accommodated. Final alignment of the assembly should always be checked and confirmed with a range rod after fitting.

The interface between the cylinder locking bolt and the open end of the extractor rod is one of the points in the assembly that is the most difficult to fit properly, and still allow for free rotation of the cylinder, and the opening and closing of the cylinder assy with minumal resistance.

There is an illustration of the front locking bolt on page 67 of Kuhnhausen's shop manual, which shows the areas on the bolt that have to be fit to the indvidual assembly. These areas include the shape of the contour or "cone" at the end of the bolt, the angle of the ramp, and the flat at the end which determines the length.

To increase contact between the end of the front locking bolt and the end of the extractor rod, (and thereby minimize side to side movement of the end of the extractor rod) you can "let out" the locking bolt by removing material from the front of the slot in the bolt body. This slot serves not only to hold the bolt in place when the locking bolt pin is inserted in the shroud, but also makes it possible for the bolt to move forward and backward under spring tension inside the cavity. Removal of material from the front or muzzle end of the slot will enable to f.l. bolt to move further back corresponding to the amount of material removed. This will increase contact with the l. bolt, and close the gauge between the end of the bolt and the front of the extractor rod.

Use caution, however, as removal of material from the slot in the body of the bolt will also change the way the end of the extractor interfaces with the end of the f.l. bolt, and these previously hand fit surfaces, including the angle and shape of the cone may have to be re-fit to accomodate the changes. This increased contact between the end of the f.l. bolt can/will also cause increased friction and inhibit the free rotation of the cylinder to some extent. This is where the "compromise" I mentioned earlier should be considered.

If you decide to try to remove gauge between these components I would suggest waiting until all the other repair work has been completed, the cylinder/barrel/yoke alignment has been confirmed as correct, and the extractor rod has been straightened. If this is the first time you have modified a front locking bolt, I would have a new one handy as a replacement if needed.

 

[Toolguy]

You should also check crane alignment to the frame with a crane alignment gage which fits into the center pin hole in the frame.

 

[iPac]

I hope you got this 629 for a next to nothing price tag. Never buy a basket case revolver for good money. It's best to factor in all of the repair costs, if skilled enough to do so, then subtract that from any asking price.

Good luck with your project.

 

[jmclfrsh]

Thank you for all your responses, I really appreciate it.

In retrospect a I am either too picky, or I paid too much for it ($900.00).

With the trigger and hammer, I have $1130 in it, so yes, a little high but I learned a valuable lesson with it on what to look for moving forward.

I also learned how to work on one, which is nice, too.

Time to just start shooting it and see what I have. If it shoots well, then I’m ok. If it doesn’t then I might put it up for sale and start all over again - but I’ll know what I’m looking for next time!

 

[cmj8591]

Could it be that the center pin is just a tad too long?

 

[scooter123]

In retrospect a I am either too picky, or I paid too much for it ($900.00).

Time to just start shooting it and see what I have. If it shoots well, then I’m ok. If it doesn’t then I might put it up for sale and start all over again - but I’ll know what I’m looking for next time!

IMO you are being too picky. The S&W revolver was designed for use in Combat, as in muddy Trench Warfare. Guess what would happen if something as simple as the cylinder stop were designed with a wedge shape and fitted into a wedge shape recess with with just a bit of dust present. You got it, the cylinder stop would jam in the notch and lock up the gun. Something you do NOT want to happen if you are fighting for your life.

To put it simply the S&W revolver has a bit of "slop" designed in so that it wont ever jam with properly assembled ammunition. There is slop in the Carry Up, slop in the Cylinder Stop, and slop between the hammer and frame and it's all there to allow the revolver to function properly even after being dropped in a pool of muddy water. It's also why all of these revolvers have a Forcing Cone in the barrel.

BTW, I have a model 620 that happens to be one of the first S&W revolvers to adopt a 2 piece Tensioned Barrel design sort of similar to what Dan Wesson introduced in the late 60's. I have personally shot 7/8 inch groups off a sandbag with this revolver at 50 yards using handgun scope and the cylinder probably has all the cylinder rock that you were fussing so much about.

So, yeah, you really need to just take it out and shoot it. If like me your eyesight aint what it once was try doing a bit of "cheating" and mount a scope on it and shoot it off a rest.