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a metallurgical question

Discussion in 'General Firearm Discussion' started by ithacaartist, Aug 19, 2012.

  1. ithacaartist

    ithacaartist Mecklenburg, NY New Member

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    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.
     
  2. Mark W.

    Mark W. Silverton, OR Bronze Supporter Bronze Supporter

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    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.
     
  3. novamind

    novamind Hillsboro Active Member

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    4130-4140 steel,Beaver heat treat in portland.
     
  4. chemist

    chemist Beaverton OR Well-Known Member

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

    iamme Lane County Well-Known Member

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    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
     
  6. ithacaartist

    ithacaartist Mecklenburg, NY New Member

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    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?
     
  7. Allfat

    Allfat Marion County Active Member

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    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!
     
  8. JoeDirt82

    JoeDirt82 NW Oregon Member

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    Regular old "tool steel" would probably work.
     
  9. ithacaartist

    ithacaartist Mecklenburg, NY New Member

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    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!
     
  10. Spitpatch

    Spitpatch Forest Grove, Oregon Well-Known Member

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    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.
     
  11. ithacaartist

    ithacaartist Mecklenburg, NY New Member

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    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)

    (sic)

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

    Velzey Estacada, Oregon Gunsmith Gunsmith Bronze Vendor Bronze Supporter

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    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.
     
  13. ithacaartist

    ithacaartist Mecklenburg, NY New Member

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    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.

    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.

    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...