[panaceabeachbum]

I know the Ti machining questions have been beaten like a dead horse but I need a little help.

I am trying to drill a hole .358 diameter in a 6al-4v bar. Bar is 1.375 diameter held in a 16c collet.

Hole needs to be 3.1" deep. I have tried peck drilling HSS bit, 600 rpm feed rate of .001 per revolution peck of .02" retract clear of part with flood coolant. I use similar feed and speed in 4340 and shallow Ti holes without issue but keep loosing cutting edge on bit with this hole approx 1" deep. I know coolant is still making it to cutting edge at this point. Just need to drill about 100 holes in the next week.

Any advice greatly appreciated.

[diamond.3211]

I would slow the RPM's down to around 300RPM's and keep the feedrate where it is which will up you to .002 per rev., there is probably some work hardening going on and that is most likely what is causing you the trouble, also an ideal bit would be Cobalt with a 135 PA with thru tool coolant, might be worth investing in. If its giving you trouble at 1"deep getting down to 3.1" is going to be a challenge.

[panaceabeachbum]

Thank You, I have cobalt bits due to land tomorrow.will try the reduced speed. I may try drilling in the mill so that gravity can help out with coolant.