Tapping 300m (4340m)

[Dave P.]

Hi all
I have a piece of 300m steel round stock
that I need to drill and tap on the ends.
Drilling is not a problem but I'm wondering
if I'll be able to tap it. Planning on
.375 about 1in. deep. The certs that came
with the material list it at 53rc.
I had no problem doing the keyways using
carbide but I'm thinking I might have to
"bite the bullet" and just pay to have
someome edm the threads. Will good quality
taps handle this?
Any thoughts?
Thank You
Dave P.

 

[Gary E]

If you mean "Maraging 300" it's going to be tuff stuff, go slow and it can be done.

If you mean "Mod 300M" it's also tuff stuff, but not as bad as Maraging steels.

ok, I re read the header where yuou say Mod 4340... it's No 2...still gona be tuff stuff... go slow...

Use High sulfurized cutting oil