8620 sounds appropriate as that's what tool holders are typical made
from. 58-60 RC sounds a bit hard (to me) for the application so I checked
some BT and CAT (40) knobs. A few of the CAT knobs were around 45 RC on
the business end and 30ish RC on the very end of the threads. The BT knobs
(which we are in need of specials of) I checked were 45-50 RC end to end.
48-52 RC sounds more reasonable to me, but I'm not Iscar or a machine tool
designer so WTF do I know? :)
Since 8620 is a case hardening material, know of any reliable ways of
measuring case depth?
This is a country where people are free to practice their religion,
Pretty sure at the lazy b whenever we used 8620 and similar steels then
travelling along the order through to heat treat we also processed a "test
coupon" made from the same lot of steel that roughly approximated the part
size /shape, and then cross sectioned it via cold saw--hardness readings
are taken from the outside and the inside of the part and finally the case
depth was measured by visually observing the depth where micro grain
structural change is actually observed either by eye or by using a
microscope if the depth was relatively shallow.
FWIW, usually a second and perhaps more coupons were also made, and used for
tensile, shear, compressive and similar (destructive) tests..
I'd send it to a lab, if I wanted reliability & it's not something
I did regularly.
A previous employer made alot of shafting and observed the micro-structure
after sectioning, as PrecisionmachinisT described previously. IIRC they
also used a method which involved passing an electrical current through the
sample. But they had a real metallurgical lab.
We decided to make them from Viscount 44. If other companies are making
them from H-13, shouldn't be a problem. It's not a high stress
application anyway, we're just going to hold a CAT 40 boring system in a
BT 40 machine with manual tool changes vs buy another complete boring
set for 1 machine.
Get in touch with your feelings of hostility against the dying light.
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