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Speeds and feeds for drilling 304 ss


Jan 23, 2021
I quoted a job on 20 qty M3X0.5 tapped holes. I have to drill and tap these on the quadrant of gear shaft collars, thankfully enough they are thru holes. I am doing these in my work horse CNC mill Bridgeport Toqcut22, tapping cycle, flood coolant, spot drill (carbide 3/16" 90 degree cm), #38 or #39 cobalt drill, .250 deep thru 1X wall...

I'm reaching out in need of help with the spot drill speeds/feeds, drill speed/feed and peck depth. My tap speed and feed will be 508 rpm & 10 ipm.. Should I form or cut the M3X0.5 threads? What material/coating type tap that will produce the most successful results in 304SS?

I try to stay away from 304/316SS jobs unless they are low carbon, but this new customer is a tech giant and I would like to get a lot more work from them.

Any hints, tips and trick are greatly appreciated! Thanks in advance!


Jun 7, 2012
I'd form tap them. Just make sure you make the hole the appropriate size before tapping, and hold that size.
Cobalt drills go about 50sfpm and .003ipr for starters.
Tap at 50 sfpm.
Get a coated tap with at least TiN coating, preferably AlTiN/TiALN coating.