best material for rifle trigger

I'm "reverse engineering" a two part FN30 rifle trigger:
http://www.mwdropbox.com/dropbox/trigger1.jpg
http://www.mwdropbox.com/dropbox/trigger2.jpg
What tool steel and temper would be best for this?
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On Mon, 18 Feb 2013 20:38:18 -0600, Karl Townsend

Id say 4140. Or O-1
Gunner
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wrote:

I'd worry about that little projection on the top piece, right where it joins the main part of it.
There's going to be a lot of residual stress there when you quench it in oil. Square shoulders with vastly different thicknesses are a real problem.
However, I don't know what I'd use as an alternative. Going to A-1 might do it, but I don't know.
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    How about D-2 -- another air hardening steel?
    Good Luck,         DoN.
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wrote:

Maybe. Custom knife makers use it for blades that take some bending loads, so...
But it doesn't relate to normal tool-steel applications that I know of. When you use an air-hardening steel in its intended application -- mostly press tooling -- it's for the same reason that I described: a thin section extending from a thick section, as with lead-frame punches and dies, and similar tools for punching other electrical connectors, or any tool that's difficult to quench safely. Those tools are loaded mostly in compression or straight tension, not in bending.
I'd ask a knife expert about his experience with D-2.
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    I doubt that it will be getting enough force to risk bending or breaking (a function of how you temper it after the hardening).
    I've used it to make circular punches for producting some parts from hard felt.

    Yes -- D2 like A1 would not need quenching -- just let it sit out there in the air after heating.
    I don't see enough load on this to make a difference. The main reason for hardening here is to minimize wear at the sear surfaces.

    My experience with the sharp edged circular punch driven by a small flywheel punch press showed no problems. I left it rather hard, and used a toolpost grinder on the lathe (with proper precision surface protection, of course) to finish the sharp edge. It mounted by being threaded some distance back, allowing adjustment of the point at which it contacts the backing plate. A previous one made of 12L14 was way too soft and the edge curled under. :-) (Obviously, the threading was also done prior to hardening. :-)
    Enjoy,         DoN.
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wrote:

I don't know the part so I can't judge. I saw the abrupt, square-shouldered transition from a thick section to a thin section, and I recognized a quenching hazard with any water- or oil-hardening steel. That's almost a perfect example of a quenching hazard.
You may overcome it and restore some bending strength with an extended tempering. That is, if you didn't set up microcracks in the first place. You're unlikely to know that until the part breaks.

That's a punch application, with compression loading, which is the intended purpose of punch-and-die tool steels. Among those are the D-series and the A-series. But W-2 and O-2 are as good, if the wear isn't a critical issue and there are no quenching hazards.

That's the whole idea of those steels. They're also quite wear-resistant, but that isn't the basic idea. The idea is to allow safe quenching with difficult shapes and trasitions.

Ok. Again, I don't know the part or the action.

That sounds like a good application. If I had some D-2 on hand, I'd go with that.
But it doesn't sound like the tool presented any quenching risks. A water-hardening or oil-hardening steel probably would have worked about as well. D-2 does have more wear resistance, however.
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wrote:

pbox/trigger2.jpg

There is a book "tool steel simplified " which is available on ABE for a few dollars. It might be something you would want to have.
As I remember it says to start with W1 and go to other tool steels if W1 does not work.
Dan
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what's the original material?
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