What does "crush fit" mean exactly

Tripwire229 · Aug 31, 2012

Just wondering what crush fit means exactly in relation to revolver barrels and barrel replacement. Does crush fit mean to literally crush the threads together and dimish the ability to use them again or does replacing revolver barrels in the factory result in a barrel fitment as good as doing it the first time?

dant · Aug 31, 2012

Its a combination of both the threads as well as the shoulders of BOTH the guns frame and the barrel body...threads are precut ( engineered to start and stop exactly the same place each time) and when the two come together, just "short" of "top dead center" ( for the lack of words) the final "oomph" twist or crunch, using the laymens terms of "crushed fit" it alll comes together, and the sightblade is supposed to be "top dead center...TOO hard a "crush" and it can go "past", causing the sight to tilt over to the left, not enough, it will tilt to the right it, and again if too tight,hard, can "split" the frame surrounding the barrel threads......
the older way of pinning things in place once fitted took too long, and extra operation or two, thus cost MORE money and time is money...they just about ALL "crush fit" the barrel to the frame,it works.
Yes, of course all has to be "normal or perfect" during this process.

and to answer your last question, if one takes off the barrel with the proper tooling,jigs and wrenches, it can "loosen" and not be as tight,snug the next time around and will cause the sight to start to go beyond "top dead center"....

Titegroups · Aug 31, 2012

A barrel is pretty much like a bolt that threads into the frame, once the shoulder touches the frame like a bolt head further turning will tighten the shoulder against the frame generating torque as the threads pull it tighter. I believe they cut the barrel shoulder back so when the barrel is at rated torque the front sight is straight up. I haven't had one apart but I would think you could remove one and retorque it and the sight should be right as long as the mating surfaces and threads weren't damaged. I have a strong mechanical background.

Alk8944 · Aug 31, 2012

"Crush fit" is a term originated by people who have the misunderstanding that earlier S&W revolvers, with pinned barrels, that the pin had anything to do with barrel retention. It simply refers to S&Ws without pinned barrels. The barrels have always been retained by torque, exactly as any form of threaded fastener.

In other words, it means current production barrels are installed exactly the same as barrels for any other type firearm where the barrel is screwed into the frame or receiver.

The barrel pin never served any barrel retention function. S&W realized that threaded barrels at times come loose due to the dynamic loads of firing. If this happened the barrel pin served as a safety, to keep the gun functional if this occurred during an emergency situation. Every brand of gun has, at one time or another, experienced cases of the barrel threads loosening. I have seen it in Colts, Rugers, Ubertis, etc.

WR Moore · Sep 1, 2012

AMEN!!!!!!!!!!!!!!!!

If we're getting real technical, what creates the torque is the threads causing the shank of the barrel to stretch slightly.

Titegroups · Sep 1, 2012

Tighten it til it loosens.

GLV · Sep 1, 2012

Barrel stub?

I think was the term used by S&W smiths to describe the condition of the barrel being unable to accept a range rod. A lot of this in the early eighties with the 686.

My 696-1 had to make two to S&W before they changed the barrel.

etexas · Sep 1, 2012

How would a gunsmith determine how they would fix a canted barrel?

dant · Sep 2, 2012

if it moves, loosens, then needs to be recut (set back) one thread.....this is if the sight has gone beyoind the "top dead center"
it all depends on which way the sight may be "canted"....righty tighty, lefty loosey....

gotta remember once the barrel is "set back" ( recut) this alters and changes everything else in relationship to the "set back" ejectors, housings ( on single actions) barrel/cylnder gap, etc........
also "how" good, neat the job was done, so as to NOT mark, mar the guns finish, causing the need to refinish ( reblue) to remove any and all the tooling, wrench, vise, damage that may happen and oh yes we've seen that happen ALL too often...some real 'schlocks' out there, or bad kitchen/backyard "gun plumbing"........

What does "crush fit" mean exactly

Tripwire229

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dant

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Titegroups

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Alk8944

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WR Moore

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Titegroups

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GLV

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etexas

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dant

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