Need Help!- Drilling 316 Stainless Plate

[SheldonB]

Any suggestions on tooling for the drilling & tapping of 316 plate. Hole size range from 1/8" to 1/2". Parts being done on a CNC mill.
HSS, Cobalt or Carbide ? or any combination. If anyone is having success drilling & tapping this stuff I would appreciate any info they can supply, especially on the small diameters . . tool manufacture, speeds & feeds, etc.

Thank You, Sheldon

[DSL PWR]

Well to start off you can use the same tooling for 316ss that you use for carbon steel. I've found that if you start off at about half the speed, and feed it usually works out. I tend to try and push the feed as much as I can so you don't work harden this stuff. Avoid peck drilling if possible (work hardening) If you are doing lots of 316ss talk to your tooling guy (or gal) and see what they have for special tools.

For general milling and for ss I like the Hanita varimills.

[pking321]

there are alot of variables when dealing with ss's versus carbon steel, i have found that 303 acts alot like cold rolled steel, while 316 is a bit more difficult, it loves to work harden as previously mentioned. But to answer the question, a good cobalt drill should give you all the performance you need, step up the tip angle from your normal 118 degrees to something a little more blunt, this allows to make less pecks(you do need to peck to evacuate chips and let coolant into the hole), as far as tapping make sure your tap is sharp obviously, also make your pilot hole a couple of thousanths bigger, if you can, maybe go 60% thread, i like to tap 316 around 1000 rpm, i feel its kind of the happy medium, plenty of tourque, but not too fast. As far as the smaller diameters, just use the same techniques as any other hole, remember speeds, feeds, and coolant coverage are the most important things when drilling and tapping, and of course dont work harden the material, or your screwed no matter what you try, good luck