I have an argument going on...or lets just say I've started an argument on another sight. I have a smith that says you have to watch out for work hardening threads on a Chrome molly gun barrel. I call bullshit but then I don't know it all, at least that's what I tell others QUESTION: Has anyone here work hardened a chrome molly barrel or stainless for that matter, by threading it to slow? I myself have never had any problems other than one chamber that chattered and was able to fix it, it was NOT from work hardening! What you say...

Work hardening comes from repeated stressing. Especially stressing past it's elastic limit. Like repeated sharp bending of a coat hanger to break it. If cutting threads caused work hardening to the point of not being machineable it would have to be some very exotic steel, not 4140. Some steels will dull a cutter fast enough to give the appearance of work hardening. Some stainless steels are notorious for that. If gun barrels work hardened then they would break after enough firings. Bullets stress a gun barrel every time it's fired. This would also mean you couldn't machine an old barrel. I put muzzle brakes on and re-crown old barrels all the time.....Tom

NO

Threads on most high strength steel fasteners are rolled to give them added strength rather than being cut threads. Even after being rolled you can still machine those fasteners like butter.

Stainless steel can be work hardened but it does not happen very often and then usually due to a drill bit getting dull.

Yea, I didn't think so. As a cnc machinist where I get my income, that is pretty much all I do is threading. I thread chrome molly, nine chrome, 13 chrome and Inconel...I know a little about threading. I've been threading and chambering rifle barrels for 29 years now , so know how to single point and such. Sorry for the rant...but this is from someone I know should know better. Both good answers above!

I call bullshit on this one. I, too, have threaded many barrels over the past 40 years and all the threads are soft. If that was the case, it would work harden if you filed on it. It doesn't.

I have a question some one here might be
able to answer about work hardening.
A friend gave me a 50 cal BMG bullet that
someone had drilled an 1/8" hole in.
He wanted a 3/16" hole drilled for a chain
to go thru to wear around his neck.
I tried to Google what the base metal was.
Believe it was a AP round
Must have work hardened. Tried every thing
but carbide drill. What the heck is that alloy

I'd bet I've cut more 4140 and 4130 than anyone here

1" KrestCut up to 6" full depth and or through at 200ish rpm or 4 insert shell mill .250 deep and let-er eat

Literally tons of cro-mo cut but work harden it? Not hardly

Ted
I might can beat you on 4140. I make
down hole tools. I run about 10 tons
a year thru my lathes.
I repair a lot of stem boxes and pins
They use pipe wrenches to tighten them up
and from the repeated stretching, like
Tapper2 stated, it will work harden.
Still workable though.

Fifty cal AP cores are made from high carbon steel, and are simply hardened by the usual method. Certainly not work hardened by the turning operation. I use them for center punches. If you want to drill one, get a ball round, which is just lead inside.

Gee I thought you guys would know !!
Almost every company now uses the roll form rifling developed by Steyr .Remington has used it from the early 70's !! So yes 4140 can work harden.Just how hard it becomes I don't know .Certainly it has to be able to be cut for threads as I don't think they roll form the threads.
Some steels cold work a lot , some a little .We make springs from work hardening 301 stainless for example ..
4140 is a fine steel for many uses but as long as you're tooling is sharp [machining 101] you shouldn't have a problem.
You should have known this but I guess that's why you need a metallurgist .

quote:

Originally posted by brad may:
Ted
I might can beat you on 4140. I make
down hole tools. I run about 10 tons
a year thru my lathes.
I repair a lot of stem boxes and pins
They use pipe wrenches to tighten them up
and from the repeated stretching, like
Tapper2 stated, it will work harden.
Still workable though.

we have several molds that tip the scale at or over 10T

All I can say is "shoot your gunsmith before he passes on the stupid gene"

quote:

Originally posted by dpcd:
Fifty cal AP cores are made from high carbon steel, and are simply hardened by the usual method. Certainly not work hardened by the turning operation. I use them for center punches. If you want to drill one, get a ball {round, which is just lead inside.

Could be I have something thing unusual but all my ball 50 cal has steel cores too. They have a lead plug in the base that makes it look as if the core is lead.

You don't have anything special; much 50 cal ball has steel cores, to save lead, but those cores are soft steel, whereas the true AP ammo cores are made from chrome-tungsten steel and are super hard.

I had read that they had accuracy problems with lead cores stripping from rotation and that was the primary reason to switch to steel cores.

I think it was in a copy of 50 Cal Shooters Assoc and why there weren't many lead core match bullets. I think the A-Max is about the only one at the time.

quote:

All I can say is "shoot your gunsmith before he passes on the stupid gene"

I am my own gunsmith...that's why I called B.S. I deleted myself from this bunch. I will not call out a name but it is someone I respected in the benchrest rifle building business. Still practicing the trade .

dpcd...we used the same tung/carbide 50 cal. as a punch in a tooling project at smithing school.