On 2013-02-20, Ed Huntress wrote:
On 20 Feb 2013 03:19:06 GMT, "DoN. Nichols"
wrote:

On 2013-02-19, Ed Huntress wrote:
On Mon, 18 Feb 2013 20:47:36 -0800, Gunner
wrote:

On Mon, 18 Feb 2013 20:38:18 -0600, Karl Townsend
wrote:

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?

Id say 4140. Or O-1

Gunner

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.

How about D-2 -- another air hardening steel?

Good Luck,
DoN.

Maybe. Custom knife makers use it for blades that take some bending
loads, so...

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.

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,

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.

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.

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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