I just ran off a small job for a customer that consisted of (40) 3/4" dia 304 stainless balls, that required drilling through the ball for M4 tap, spotface around each end of the hole, and tapping through. I did this job on my lathe with bed turret, and it went rather well, no real complaints. But, in the course of drilling the parts, with a cobalt twist drill after center drilling on the spotface, I saw large variation in the behavior of the drill from part to part.
I did manage to get through the 40 pcs with one drill bit, but I saw/heard a lot of popping and snapping after the drill was about half-way through, but also not on every part. I also heard similar noises from the tap, if I really got the tap moving (did these by hand, in the lathe chuck, to avoid breaking a tap). Drilling and tapping done with Relton Rapid-Tap as lube. My question is whether this is just variation in material properties on 304 from part to part.
I did manage to get through the 40 pcs with one drill bit, but I saw/heard a lot of popping and snapping after the drill was about half-way through, but also not on every part. I also heard similar noises from the tap, if I really got the tap moving (did these by hand, in the lathe chuck, to avoid breaking a tap). Drilling and tapping done with Relton Rapid-Tap as lube. My question is whether this is just variation in material properties on 304 from part to part.
