Re: Metal selection 101

Hi Lee, et al
Understand that everyone has their preferences for
steels, etc.
Mine are:

8620 easy to machine but a little gummy;
can be quenched in oil or water and will give
decent hardness for many applications w/o
carburizing. e.g. Rc 38-42 on quench and temper.
If you need a really hard case then go ahead and
carburize, quench and temper. For fancy
apps....carburize, cool, quench from 1550, quench
from 1450. Give really nice fatigue values.
(e-mail me if you really care :-) )

4140 because of the higher C content more
difficult to machine. Hardens deeper than the
8620. Oil or polymer quench.

4340 deeper hardening than 4140. Easier than
4140 to find in the Seattle area because of the
aerospace applications.
There was a ton or so of 4340 /300M at Boeing a
few weeks ago.... $0.25/lb. :-)
Because of it's deeper hardening characteristics
consider 4340 an upgrade from 4140.

A10... air hardening , low quench temp and
therefore low distortion. easy to machine because
of the spherodized carbon content.

A6 - if you can get it... a nice balance (for a
tool steel) between hardness and toughness.

D2 - very hard but brittle by comparison.

H13 - consider for very high impact
applications....really tough if you temper back to
Rc 38.

S7 - designed for high impact toughness.

Hope this helps some.

Dave