Gunsmithing Surface Hardening compound?

rg1911

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I recently worked on the trigger on one of my AR-15s and had my 'smith harden the surfaces of the hammer and sear since I'm pretty sure I broke through the original hardening. He used a product from Brownell's that he bought 30 years ago and that he said is no longer made since California decided it causes cancer.

I found this on Brownell's site, but it's out-of-stock.

SURFACE HARDENING COMPOUND | Brownells

Although the can looks similar, I don't know if it's actually the same stuff.

Are there other good products that would be available? I'm interested because it's a 140-mile round-trip to my 'smith and I have more work I'd like to do.

Thank you,
Richard
 

Horseheadman

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Do a search for " Kasenit Surface Hardening Compound " I've looked in my regular suppliers and didn't find it. Brownells, or Midway usually carry it, but they are out of stock. Did see some selling on Ebay and a welding supplier may help you out too... Good luck
 

callen3615

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Id like to know this too. Ive done some trigger work on a few of my handguns and id like to harden up the engagement surfaces.
 

MarinePMI

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    Ditto Horseheadman's recommendation...

    Kasenit has been around forever, and used exactly for this. I suspect what Brownells sells is either Kasenit in their house brand tub, or a chemical copy of it.

    If you get really hard up, you can make it yourself (not rocket science, as gunsmith's used to consider this sort of thing normal fare with their profession). One of my older (read turn of the century) gunsmith book's has a recipe (so many parts bone meal and charcoal IIRC). I check to see if I can locate it...(I'm thinking Howe's book on Gunsmithing had it)...
     

    671RTO9513

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    I get Kasenit from MSC or McMasterCarr, can't remember which. One is a helluva lot cheaper than the other. I fill a small tuna can with the kasenit and small parts buried in it, and the whole lot goes in the furnace at 1650 degrees for 40 minutes, then I pull the can and individually plunge the parts into water. Saves a lot of popping and water going everywhere like when you dump the whole lot in at once. Then I draw for an hour at 350 degrees. This is what works for me.
     

    Wolfkin

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    Depends on the metal or % Moly and mostly % Carbon in iron

    I case harden 4130 by heating to nonmagnetic with map gas
    then quickly dunk in vegetable oil next place in 300 degree activated carbon fines or can use charcoal ashes
    the item comes out looking deep black like its been blued and hard
    this works also with most tool steels

    A Woodworker's Guide to Tool Steel and Heat Treating
     
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    McLarenross

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    Depends on the metal or % Moly and mostly % Carbon in iron

    I case harden 4130 by heating to nonmagnetic with map gas
    then quickly dunk in vegetable oil next place in 300 degree activated carbon fines or can use charcoal ashes
    the item comes out looking deep black like its been blued and hard
    this works also with most tool steels

    A Woodworker's Guide to Tool Steel and Heat Treating

    Ditto but I dunk in used motor oil, the dirtier the better. Super high carbon content in the oil and the steel absorbs that under the intinse heat.
     

    671RTO9513

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    Ditto but I dunk in used motor oil, the dirtier the better. Super high carbon content in the oil and the steel absorbs that under the intinse heat.

    This is bullshit. The correct oil to use is proper quenching oil. I was at my heat treater's the other day (he does my large lot case hardening) and we were discussing this. There is no telling what you're doing to the steel in used motor oil, but I'll wager it ain't putting carbon in it. And I'm not a betting man. The results are at best, unpredictable.

    My heat treater had just filled the quench tank on one of the furnaces - 3000 gallons at $10 a gallon. You do the math. If used motor oil was OK he'd have used that - been a helluva lot cheaper.

    Go to a local heat treater, most of them will be happy to put 2 or 3 gallons in a bucket for you, which is good for most small shop jobs.

    I hope I didn't upset anyone, but I'm tired of hearing this used motor oil myth.

    BTW Don't forget to heat the oil to 90 to 130 degrees before you quench the item. I use a crockpot.
     
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    Wolfkin

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    You are right used motor oil will very the carbon %results, so does case hardening do to carbon material size used contacting the surface metal, the surface hardening paste works best due to its uniform contact and depth of hardening for a deep scuff resistance surface.
    the methods used very from any manufacturer due to their end use, I called three and received a different answer for the same hardening question???
    I use clean vegetable oil because it works for my apps but is low in hardening depth
    If you want to know how hard they do make hardness testers!
     
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    xs hedspace

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    The surface hardening thing is based on adding carbon or nitride to the steel--different than just heating and dunking. Kasenite is used by heating the part to cherry red, dunking it in the Kasenite powder, then reheating, so the kasenite melts on the surface to be hardened. Then quench in cold water. If you go to Howes' book you will find a recipe that calls for Ivory black(ivory charcoal) and sperm whale oil. Lots of luck finding them, nowadays!!
    PS: It depends on the steel of the sear and hammer whether the surface treatment is needed. If the item is high carbon steel, the original hardening will be all through the part, not just on the surface, so you can polish, and forget the casenite. You can test on the side of the part, if it can be cut with a file, you need casenite.
     
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    671RTO9513

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    As with all heat treating, the first thing you have to know is what steel you're dealing with. Otherwise it's a shot in the dark. If you've done enough, a grinder test can give you an idea, but it's still a guess.
    Case hardening is for low carbon steel. It allows parts to be made with a relatively soft but very tough core, that's how most gears are still made. Mild 1018 will make a very durable part if case hardened. 8620 is probably the most widely used steel for case hardening in industrial applications, it has nickel added to improve core strength, which also makes it machine very nicely.
    I would not case harden 4130/4140 or high carbon steels because a brittle part will result. Breaking off small chunks here and there (sear noses and such, which would obviously be bad for business).
    Rockwell testing the surface hardness of case hardened parts is difficult without very specialised gear because of the softness of the underlying substrate.
    I have bored out gears for larger bearings and shafts, and have seen case hardening to depths over .070". Of course, this is not necessary with what we're doing.
     

    Wolfkin

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    I agree hardening without knowing the original % carbon is a shot in the dark for the end result may become brittle, hardening 4130 type steel is not recommend its already strong enough for most apps, I do it mostly for the black color effect of a barrel shroud and its scuff resistance. Any internal gun parts (like FCG or firing pins) I use the hardening compound paste. Note most ak47 receiver manufacturer sites did recommend to harden the pin holes in the 4130 steel receiver buy just heating the hole area with a torch. There is a video online how to harden the hole receiver without warping it.