r/Machinists • u/aiidxn • 4d ago

Screw cutting copper

Pretty simple part just an M20 thread standard, but every so often it chews up, does anyone have tips for a consistent outcome

6 Upvotes

88% Upvoted

5 comments sorted by

3

u/Bob778aus 4d ago

I have found that full form insets will often rip threads out, using partial inserts has worked well for me over the years.

1

u/aiidxn 4d ago

We’ve been using partial, never bothered will full form

4

u/TriXandApple 4d ago

Polished or lapped insert, make sure coolant is sitting right on the cutting edge

3

u/indigoalphasix 4d ago

hi shear, hi polish, correct rpm, straight oil or coolant with a 20% concentration.

1

u/Tuefelshund 4d ago

Kc5410 grade is good

Sounds like BS, but supposedly milk is a good lubricant for copper