a metallurgical question

ithacaartist · Aug 19, 2012

Hello, all, new member here...

Does anyone have knowledge of what specific steel alloy would be used to create an extractor? Also, any advice on heat treating same?

Thanks,

D.P.

Mark W. · Aug 19, 2012

That would most certainly depend on the the specific firearm. And could even depend on the generation of the firearm. There are at the very least many dozens of different alloys used to make various gun parts, each requiring there own heat treating profile.

You need to be much more specific to even have a chance of finding out what alloy the manufacturer used at the time you firearm was made.

novamind · Aug 19, 2012

4130-4140 steel,Beaver heat treat in portland.

chemist · Aug 19, 2012

4140 Cr-Mo steel is kind of a universal choice for guns

iamme · Aug 19, 2012

Mark W. said:
That would most certainly depend on the the specific firearm. And could even depend on the generation of the firearm. There are at the very least many dozens of different alloys used to make various gun parts, each requiring there own heat treating profile.

You need to be much more specific to even have a chance of finding out what alloy the manufacturer used at the time you firearm was made.

Mark nailed it. Being an extractor with most guns will probably not be highly critical what metal you choose, but others will be very important. The next two answers give you an idea of what is very common, but not necesarily what you'll need

ithacaartist · Aug 21, 2012

Thanks, Mark, et al.

My initial questions were posed in relative ignorance, however, I hope, not total. The extractor in question would be for the KGP68a series, made by the now-defunct Erma-Werke in Germany. These pistols apparently have a reputation for throwing their extractors, as I found out while looking for a replacement for one of mine that launched its extractor into unknown parts of the stratosphere on the very first trial mag the day it arrived. The design is similar to the P.08 Parabellum (Luger), a pivoted claw that hooks over the top of the round when in battery, from its position in a slot in the top of the breech block.
I'm not sure that its function is all that exotic in this pistol. I'm hoping, Mark, that this brief description helps with a more definitive answer.
Carbon steel generally varies in hardness and toughness, either aspect being inverse to the other. For longevity and durability, I'd think it would need to be at least a little harder that the brass cases with which it interacts, while being tough enough not to break under the repeated pounding. But it also pivots in its location in the breech block, so should be slightly less hard than whatever the block is, to minimize wear at this interface. Would there also be a Rockwell number, generally, that would work for this application?

Allfat · Aug 21, 2012

Sounds like you need to do some testing!!!

Seriously, I doubt anyone knows the rockwell hardness of the breech block in your gun, so the way to find out is to test your breech block and a brass casing to find their respective hardness, then pick a hardness in between those numbers for your extractor. I think you are on the right track though. Good luck in your search!

JoeDirt82 · Aug 23, 2012

Regular old "tool steel" would probably work.

ithacaartist · Aug 23, 2012

It's coming together, I think. At this point I'm inferring that it probably isn't that exotic, and I have a sneaking suspicion that JoeDirt might be onto something, here. 4140 not out of the running yet, though. In case there are no further suggestions, try my other thread in Gunsmithing and Repair, where I ask how to refinish Zamak parts!

Spitpatch · Aug 25, 2012

Ithacaartist:

I thought I was the only guy on the face of the earth with a KGP68. Save yourself a lot of time, effort and metallurgical experimentation and contact Jack First in Rapid City, South Dakota. 605-343-9544. This little outfit tools up for all kinds of parts unavailable elsewhere, and I do believe it was an extractor that I ordered from them for my KGP.

ithacaartist · Aug 25, 2012

Well, the idea was to create a modified version of the original KGP68 extractor's design--one with an extended "tail" and a deeper detente. If the success claimed by the originator of these modifications bears out, the modified part would negate the need to keep buying extractors, since these new ones would stay put and not be thrown off the gun. I see no need to have someone else do work or design that I can do myself. All I need now is a machinist to produce the blanks, and there is plenty of local talent. (e.g, there are two different manufacturers of turbine blade assemblies within 10 miles of each other here.) I'll fine tune the shape and heat treat myself, so may actually wind up in "competition" with Jack First in this respect!

I received the following information from an advanced gunsmith/manufacturer, Eugene Golubtsov (lugerman.com)

I do not know much about KGP guns or there constriction,
For a Luger p08 extractor I'd use 4140, heat it till cherry red, dup it in
oil, and then sand blast and dunk it in hot solt at about 500-550 till
purple blue, that will make it in to 52-55 hard.
If it's a spring loaded extractor then 1095 is perfect for it, same head
treatment.

(sic)

Is this the ticket? Let's wait and see, still open to all info.

Velzey · Aug 25, 2012

Manufacture of turbine blade assenblies wont have a clue on how to make a extractor. You need a real machinist, not a CNC machinist...at least at first. When you get your proto type done, then you will need the cnc guy.

Tool steel will work, Ive made them out of 4140, D2, A2. Heat treat is critical as if it is to hard it will shatter. 4140 is a good choice also. I made a few out of it and it cost me $35 to heat treat. 50-55 Rockwell C scale is about where you want to end up at. 55 being on the hi side and slightly brittle.

Heating it till cherry red is kinda hard to do, as it is so easy to get it to hot, or not hot enough. But its easy to grab any small piece of steel (same as your using) and test your heat treating prior to doing it on the real thing.

ithacaartist · Aug 25, 2012

Velzey said:
Manufacture of turbine blade assenblies wont have a clue on how to make a extractor. You need a real machinist, not a CNC machinist...at least at first. When you get your proto type done, then you will need the cnc guy.

My point was that my locale is not a tech-starved area. Good gunsmiths, machinists, and fabricators have one main thing in common in that they are all good mechanics, adept at understanding how things happen in this realm, their vision sharpened by talent and experience.

Tool steel will work, Ive made them out of 4140, D2, A2. Heat treat is critical as if it is to hard it will shatter. 4140 is a good choice also. I made a few out of it and it cost me $35 to heat treat. 50-55 Rockwell C scale is about where you want to end up at. 55 being on the hi side and slightly brittle.

Thanks for the numbers. A consensus is developing among gunsmiths, particularly about the likely utility of 4140, and the R numbers are in basic agreement.

Heating it till cherry red is kinda hard to do, as it is so easy to get it to hot, or not hot enough. But its easy to grab any small piece of steel (same as your using) and test your heat treating prior to doing it on the real thing.

Never fear! My son has an electric kiln and pyrometer so heat treating will not be a problem. * added* --> Alternately, placing the part on a pre-heated firebrick or soapstone will help when applying the heat. The tempering can be done in a salt/sand box in a toaster oven. Just need accurate temp maintained...