Having a tough time drilling out a stainless tube.

by Joey Mac
(Akron Ohio)

I have a piece of 18-8/304 stainless tube, 12.5mm OD x 10mm ID. I need to open up the ID to ~10.5mm to a depth of 3". So far I have toasted two bits trying to do this... a black oxide and bright HSS drill.

I'm not sure why removing 0.5mm is giving me such a hard time. I'm using a lube/cutting fluid applied by hand and running at ~300rpm (drilling SS ~13/32") and the bit is being held in the tail-stock on a chuck. As soon as it hits the workpiece I'll get maybe 1/4" into the work and it getting HOT (smoking & sizzling cutting fluid). I'm not sure why it's toasting brand new sharp bits trying to remove very little material.

Another problem is that as soon as the drill bit starts to cut into the workpiece the work tries to "grab" the bit and literally pulls the whole chuck out of the tailstock. With my free hand, I have to fight tailstock chuck rotation which feels very unsafe to me. I have a feeling that this because there is nearly no material in front of the drill bit and the twist on the bit is behaving like a screw with little to stop it.

Thank god This surface does not need to hold any sort of decent surface finish. so far the first inch of this tube I've been drilling looks pretty ugly and I'd rather not destroy 5 more bits finishing this hole.

Any tips on opening up stainless tubing very slightly?