Slow timing on one cylinder - can fix?

[WR Moore]

Something I didn't notice being mentioned is to check the yoke alignment before assuming you need to start doing other things. Yeah, if the cylinder closes, it "should" be close enough to work correctly, but we're not talking about major dimensional changes here.

 

[armorer951]

I was just wondering if "peening" the offending ratchet is the factory approved way of repairing the DNCU issue. The reason I ask is not so long ago, the "old gunsmith's trick" for performing this repair was to peen the end of the hand in order to lengthen it just a smidge. Unfortunately, carry up is controlled by the width of the hand and not the length. There was quite a spirited debate about that one with the proponents swearing it was taught at the factory. However, no factory trained personnel came forward to verify this as nearly as I can remember. I can recall so-called professional gunsmiths removing sideplates via prying with a screwdriver. Not a methodology I would recommend although it may work for some. The have been similar debates about repairing endshake with shims vs yoke repair although I believe that the factory now used the shimming method. So....., I'm just wondering what method the factory taught. This is not a debate regarding the durability and effectiveness of the ratchet peening but rather if it's a factory approve & utilized repair procedure.

Bruce

Peening is not the S&W factory method of repairing DCU. A new, slightly larger hand is fit to the extractor. If the extractor ratchets are too worn for a new hand to be fit to correct the carry up, then a new extractor would be fit.

See post number 5.

 

[BruceM]

Peening is not the S&W factory method of repairing DCU. A new, slightly larger hand is fit to the extractor. If the extractor ratchets are too worn for a new hand to be fit to correct the carry up, then a new extractor would be fit.

To be honest I suspected this to be the case. Thanks for verifying that fact.

Bruce

 

[WR Moore]

Just to add some explanation to this on "fitting a hand", the S&W hands use thickness to get complete carryup. There's really no fitting involved*, if the hand fills the hand window properly, the cylinder carries up and is locked by the cylinder stop with the cylinder properly ranged. I don't know if ratchets are still individually fit, but that's also the way the ratchets were individually cut (in the frame) at the factory.

On a K frame, the standard hand thickness runs ~-0.094-0.095 inches. The oversize hands (available from Brownells) run 0.002-0.003 inches thicker. Supposedly at one time hand to 0.010 inches thicker were available, never seen one. This is almost always sufficient to take care of normal wear.

I recently got two K frame oversize hands. One was 0.097, one 0.098 inches. The thicker one dragged on the hand window, since I had one thinner, I installed that one. If I'd had no thinner one, stoning the thickness of the hand is better than enlarging the hand window (Yeah, I've got the file, never used on the hand window. Have deburred the cylinder stop window.) This solved bad carryup on two chambers without issue on the others-yes a new cylinder stop and spring had been fitted. As has been noted, once the cylinder carries up, the hand slides past the ratchets.

*OK, if you're a purist, the hand could be deburred, and edges barely broken on several points where the hand meets the ratchet. But that faint edge breaking (or the deburring) isn't done at the factory, it's done by specialists building guns aftermarket. Trying to explain it without a video is darn near impossible.

 

[armorer951]

The problem is, the new, uncut ratchets are oversized, so much so that each individual ratchet tooth has to be cut to accomodate the hand, even the nominal sized hands........and they have to be fit not only to the point where carry up is achieved and the cylinder locks into place.....but past that point, so the hand doesn't bind when passing between the ratchet tooth on the inside the hand, and the hand window on the other side.

If the cylinder doesn't carry up after years of use and the failure is due to wear of the components (ratchet), an oversized hand is installed, and the ratchet(s) are "re-fit" to accomodate the larger hand.

 

[WR Moore]

Given that S&W now sells complete cylinder assemblies, I have the sneaking suspicion that the new design ratchets are machined/fit to a certain specification that's pretty much intended as a "drop in". CNC machining generally has much less dimensional variation than human performed machining. They certainly aren't asking for a PN on a ratchet cutter before sale. Possibly you can enlighten us.

I've only installed 2 or 3 oversize hands in 30+ years, all but the one last night were on older guns with hand cut ratchet fits. The one last night on my own piece (new design) and, IIRC, all but one of the others was selective assembly: I tried hands of different thicknesses and achieved drop in success. Decades later I can still remember the PITA of the other fit. It's why, in the extremely rare cases I buy certain parts now, I buy several. The leftovers can be stock for my kids/grandkids or trading beads.

Beats beating on the ratchet with a hammer (cringe).

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