Threading 304L VIM/VAR

[cam53]

Been having trouble threading I.D. > 304L stainless vim/var <,keeps chipping tip of insert. Using ic 528 grade Iscar I.D. insert .The thread is 1-16 tried all the recommended sfpm.Only getting about 4 parts/per insert.Using a g76 cycle
depth of .005 to .008 on first pass..005 seems to do best but takes alot of passes at that depth.
Any recommendations, on SFPM or I.D. inserts and grades or cutting oils,best suited?

Thanks ,

[shay z]

try Vardex VTX grade.

I am making ACME 5TPI 90 mm long on 22 mm diameter and the insert holds about 90 Pcs per tip/

[tobyaxis]

Try using the G92 Threading Cycle to Taylor your Depths of Cut. Always cut beneath the skin of the previous cut even with the spring passes.

304L (the "L" is Low Carbon) watch for work hardening, keep coolant slightly rich and constant.

[g-codeguy]

Originally Posted by cam53 Been having trouble threading I.D. > 304L stainless vim/var <,keeps chipping tip of insert. Using ic 528 grade Iscar I.D. insert .The thread is 1-16 tried all the recommended sfpm.Only getting about 4 parts/per insert.Using a g76 cycle depth of .005 to .008 on first pass..005 seems to do best but takes alot of passes at that depth. Any recommendations, on SFPM or I.D. inserts and grades or cutting oils,best suited? Thanks ,

Make sure to use something like Q30 in the first block if running the 2-block G76. You can make less passes by increasing the Q-value in the second block and then fudge the P-value. Make it larger also. This will decrease the depth of the first pass, yet not increase the number of passes as dramatically as leaving the P at the correct thread height and decreasing the Q will. We mostly use Seco CP500 and Kennametal KC5025 for threading. Seem to work better for us than the Vardex inserts. I run 316/304 SS at 365 sfm.

Too slow an sfm causes chipping. Cutting over a chip will cause insert chipping. I much prefer an O.D. thread.

[tobyaxis]

Originally Posted by g-codeguy I much prefer an O.D. thread.

I think most of us do, LOL