J-Frame Yoke Swap???

[snubbiefan]

I have been playing with a model 38-2 and a model 640 ND. The cylinder and yoke assemblies are completely interchangeable. The yoke stamp on the 640 is 1-172.

I ordered a SS cylinder and yoke assembly that would supposedly fit this family of pre j-mag frames. The new cylinder fits perfectly in either the M38 or the M640 and the BTCG is practically the same using the 1-172 yoke from the 640.

I was sent a yoke assembly stamped 375, which will not fit either weapon. The rod will not slide deep enough into the frame to allow lock-up let alone get close to spec. BTCG. The measurements on both the 1-172 and the 375 are the same.....except for the depth of machining at the base of the rod-to-crane junction. The "rod length" is around .006 too short.

Yes....I know that Smith says this is suppose to be a factory-fit job, but since when did a tinkerer like me pay any attention to that. I know many folks have swapped cylinder and yoke assemblies among the right "family" of frames. Did my M640 to M38 swap simply work by pure accident? Or....did I get the wrong yoke assembly?

I can probably take this yoke to a Smith or machinist and have it turned-down to match the 1-172, but I would rather find a SS yoke that fits the M38.

Is any of this making any sense to anybody?

[WR Moore]

Yoke to frame fit was by selective assembly. That is, the assembler pulled a yoke out of the parts bin and tried it in the frame. If it fit, a cylinder assembly was then tried for fit. If it didn't fit, it went into another bin and another was selected for an assembly try.

Now then, your description sounds like the yoke shaft isn't correctly machined (part discarded as bad). Facing that part of the yoke by turning would require creation of a tool long enough to reach the length of the yoke shaft & allow the yoke barrel to revolve around the shaft during machining. Alternatively, correction could be done with a specially ground hollow end mill to fit over the yoke shaft. Neither is going to be cheap, much less reasonable.

I'd suggest you contact your source of the yoke and explain that it's out of spec and try to return it for one that is within spec. The numbers stamped on them could be various things, including an ID on the machine/machinist who made them so that excessive rejects can be backtracked for correction on setup, tooling or work practice. They could also ID yokes intended to fit specific models.

PS: those who swap yoke & cylinder assemblies and find themselves within spec on all tolerances should be buying lottery tickets instead.

[Tyrod]

Snubbie are you at it again? Next thing you know, you'll be trying to fit a 500 magnum cylinder on a Terrier.

Just kidding, don't have a cow.

[snubbiefan]

I think Mr. Moore hit the target and I suspected that all along. This guy from which I purchased the parts from says he had a truck-load of new take-offs and I am pretty sure I received a yoke that would not fit anything. W R is right....it's just not machined deep enough and a special tool would be required to machine it and make it fit, which is not worth the effort. To be exactly sure of the fit, I would likely have to send it back to S&W so they could sort through the pile and find one, or find a smith that had a stack to sort through. I think I am just stuck with a yoke that will fit "some" gun out there, but none of the ones I have. All my other jays will except and swap yokes....but this one won't work with any of them. Oh well....at least the stainless cylinder assembly works and I got all the guts along with it, so that much was a fair deal and it was less than a S&W price for the cylinder alone. I will contact the seller. but I doubt he will do anything about it. At's life I guess. I actually got lucky with the 640/38-2 swap. When I change the yoke and cylinder from either gun to either gun....the BTCG is within .001 difference (around .004-.005) between either....so it can be done.

Tyrod......I am a bored retiree and a natural-born tinkerer. I will play with anything up to the point of not breaking it. This 38-2 home-made duo-tone really looks cool....just wish I could find a stainless yoke to fit and I will sooner or later.

[Double-O-Dave]

Originally Posted by snubbiefan

Tyrod......I am a bored retiree and a natural-born tinkerer. I will play with anything up to the point of not breaking it. This 38-2 home-made duo-tone really looks cool....just wish I could find a stainless yoke to fit and I will sooner or later.

Here is my Model 38 no dash with a nickeled cylinder and smooth faced, and broad (wide) combat trigger. I was looking for a stainless steel cylinder, but got a good deal from a fellow forum member on he nickeled cylinder and other parts. I also exchanged the hammer from the donor Model 38 on my Model 60-7, which makes a bit easier for pocket carry.

Best of luck,

Dave

[snubbiefan]

See Tyrod.....there are more of us nuts out here!

I WILL find a SS yoke to fit my 38-2 sooner or later.

[joeyjr]

I have a j frame 22lr that I would like to find a 22magnum cylendar and crane for ; can any one help ?

[snubbiefan]

People here will tell you that you really don't need to do that. I believe the convertibles have a 22MAG bore, which is slightly larger than the 22LR.

Having done a few cylinder swaps....it's better done by a smith, unless you get lucky and they drop in. My experience has been....it's a toss-up.