OFCC University - Metallurgy 101 (Steel)

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Re: OFCC University - Metallurgy 101 (Steel)

Postby Morne » Fri Sep 30, 2011 6:54 am

curmudgeon3 wrote:
One question: "HRC"? Is that the same as Rockwell C? If so, what's the "H" stand for?

Hardness.

Hardness Rockwell C-Scale

It's one of the more common hardness scales used to test steels. You'll also see BHN (Brinell Hardness Number) used.

Important note - hardness is not everything. While it does correlate fairly well to ultimate tensile strength (UTS) for quenched-and-tempered steels even that rule has some notable exceptions.
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Re: OFCC University - Metallurgy 101 (Steel)

Postby Pessimist » Tue Oct 04, 2011 5:19 pm

Thanks!

So I see mention here of forging the rifling into barrels. Can you tell me anything more about that?

Do they start with DOM tubing, or do they pierece a bar during forging?

I was involved in metal cutting rather than forging, but we did have a relatively modern forging shop in the company and I visited it a few times. It seems like it would be hard to get the rod with the rifling (would it still be called a die?) out of the barrel after forging. No?

Plus, aren't forgins not all that accurate? (Die wear, shrinkage of the part, etc.)?

Presumable they finish bore afterwards?
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Re: OFCC University - Metallurgy 101 (Steel)

Postby curmudgeon3 » Tue Oct 04, 2011 10:05 pm

In this instance "forging" might be a misnomer; seems like a barrel-rifling operation would be more coducive to an extrusion process. Not sure about that though .... that technology is a little above my pay-grade.
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Re: OFCC University - Metallurgy 101 (Steel)

Postby Morne » Wed Oct 05, 2011 6:50 am

Pessimist wrote:So I see mention here of forging the rifling into barrels. Can you tell me anything more about that?

Do they start with DOM tubing, or do they pierece a bar during forging?

The classical method of barrel manufacture is to start with rolled bar and drill out the bore. That's why we call it "gundrilling". :idea:

Putting the rifling in is its own separate step. Again, the classic method uses a broaching tool that is slid in and out of the bore while the barrel rotates on rollers. At the local outdoors show they always have a great demonstration of this technique using antique tools.

Other options include EDM machining the grooves and forging them. In the case of forging they insert a "die rod" down the barrel and then force the barrel against it. They then rotate it how ever many degrees (depending on groove number) and repeat. While I am not 100% certain, I am pretty sure that they hone the barrel's inner diameter afterwards.
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Re: OFCC University - Metallurgy 101 (Steel)

Postby jeep45238 » Wed Oct 05, 2011 8:14 am

THe only rifling technique I'm aware of that doesn't require honing after the initial machining is EDM Morne. If that requires it, well, we need to talk to S&W then....
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Re: OFCC University - Metallurgy 101 (Steel)

Postby Morne » Wed Oct 05, 2011 8:15 am

jeep45238 wrote:THe only rifling technique I'm aware of that doesn't require honing after the initial machining is EDM Morne. If that requires it, well, we need to talk to S&W then....

I've been on a telecon with S&W's Chief Metallurgist. I wasn't overly impressed.
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Re: OFCC University - Metallurgy 101 (Steel)

Postby jeep45238 » Wed Oct 05, 2011 9:05 am

Honestly, I've only been impressed with one metallurgist that I've had the pleasure to chat with.

The rest of them - I wish they had one arm (you'll probably get the joke).
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Re: OFCC University - Metallurgy 101 (Steel)

Postby Pessimist » Wed Oct 05, 2011 5:32 pm

Morne wrote:
Pessimist wrote:So I see mention here of forging the rifling into barrels. Can you tell me anything more about that?

Do they start with DOM tubing, or do they pierece a bar during forging?

The classical method of barrel manufacture is to start with rolled bar and drill out the bore. That's why we call it "gundrilling". :idea:

Putting the rifling in is its own separate step. Again, the classic method uses a broaching tool that is slid in and out of the bore while the barrel rotates on rollers. At the local outdoors show they always have a great demonstration of this technique using antique tools.

Yeah, I've seen those rigs, most recently at the Henry Ford museum last year.

Other options include EDM machining the grooves and forging them. In the case of forging they insert a "die rod" down the barrel and then force the barrel against it. They then rotate it how ever many degrees (depending on groove number) and repeat. While I am not 100% certain, I am pretty sure that they hone the barrel's inner diameter afterwards.


When you say EDM, I presume you mean ram EDM, since wire could not do the required spiral. Seems to me ram EDM would make the barrel prohibitively expensive. I suppose they can gang 'em to get around some of the cyle time. Or maybe that's one reason guns are so expensive.
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Re: OFCC University - Metallurgy 101 (Steel)

Postby Pessimist » Wed Oct 05, 2011 5:51 pm

FWIW, found this online re barrel making, including "button rifling". http://www.lasc.us/RangingShotBarrelMakingFeature.htm

I've seen "roll taps" used in machining (no cutting edges) and they seem to work pretty good, so I guess this is sort of similar.

I notice this guy mentions the single cutting edge used in gun drilling. I know that to be true. It seems like the worst possible way to minimize runout, but it works. They sometimes use support pads on the back of the drill so it supports the edge against the cut. As to why use just one cutting edge? One big reason is that the cross ectional area of a 2 fluted drill is not that great. When you start getting up there beyond 30 diamters in depth or so, it's easy to snap the drill.

The single flute gives a much better section modulus.
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Re: OFCC University - Metallurgy 101 (Steel)

Postby CCWInstructor » Mon Jul 02, 2012 10:00 am

I liked this class. To bad that uneducated types have learned to type.
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Re: OFCC University - Metallurgy 101 (Steel)

Postby glocksmith » Thu Jul 16, 2015 7:36 am

A bit off topic, and not about steel, but since you guys know a lot about metal I thought I'd ask about some powered metals I brought back from my grandfather's basement. I was curious if there were any safety issues with exposing them to fresh air for the first time in decades. He had some of those tin lid Mason jars with things like powdered Nickel, aluminum etc. I was browsing Youtube yesterday and somehow came across a guy talking about making "dark aluminum" and he mentioned something about it spontaneously igniting. That reminded me of the jars I had downstairs. They haven't been opened for decades AFAIK and I was wondering if it would be safe to remove the lid. The nickel is the consistency of flour and pitch black - would the shock of a blast of fresh oxygen cause any problems?
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Re: OFCC University - Metallurgy 101 (Steel)

Postby Morne » Thu Jul 16, 2015 8:03 am

glocksmith wrote:A bit off topic, and not about steel, but since you guys know a lot about metal I thought I'd ask about some powered metals I brought back from my grandfather's basement. I was curious if there were any safety issues with exposing them to fresh air for the first time in decades. He had some of those tin lid Mason jars with things like powdered Nickel, aluminum etc. I was browsing Youtube yesterday and somehow came across a guy talking about making "dark aluminum" and he mentioned something about it spontaneously igniting. That reminded me of the jars I had downstairs. They haven't been opened for decades AFAIK and I was wondering if it would be safe to remove the lid. The nickel is the consistency of flour and pitch black - would the shock of a blast of fresh oxygen cause any problems?

Probably safe to open the jars of anything except alkali metals (Lithium, Sodium, Potassium, etc...).

What gets dangerous is when you apply heat or an aggressive source of oxidation to a powdered metal. Then the large surface area of all that metallic powder reacts very rapidly and can get interesting quickly. Consider that Thermite uses metallic powder. :idea:

One route of providing heat is friction. Thus, some of the things suggested in those videos, like ball milling in a tumbler, are inherently risky. Cooling it off intermittently by opening the drum (and thus exposing it to fresh oxygen) might even be more hazardous.

In short, making powder metallurgy supplies is best left to the experts with the right equipment and expertise. If you're not a professional fireworks manufacturer or powder metallurgist I would highly advise against it. Frankly, even with my knowledge of metallurgy, including a fair bit of aluminum work and some powder metallurgy work, I would not attempt what you have seen on the videos. I tend to like my house and skin unburnt. 8)
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Re: OFCC University - Metallurgy 101 (Steel)

Postby glocksmith » Thu Jul 16, 2015 8:30 am

THanks Morne. I wasn't planning on doing anything with it, just seeing that video reminded me of the stuff downstairs. Not sure what I'll do with the stuff...maybe just shelf it and let it sit around like Gramps did.
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