drilling/milling 420 Stainless

[Clawsie Machine]

I just got in a rush job to mill and drill some parts in this material. Any suggestion before I start? The milling won't be to bad, but the drilling I'm worried about. Just using HSS drills, FLOOD coolant. Thinking of low RPM's like 750 and 3 IPM with .075" peck on a .343 drill, what do YOU think? Thanks, John

[AMCjeepCJ]

I do this a LOT but it's been months since my last order... Crap, I can't remember the rpm's etc. but you're going to burn them up when you break through the back, so if you start having trouble, check to see if you're having problems starting there...

I think your rpm's are probably double what you should run but like I said, it's been six months or so but once you get dialed in 410 and 420 SS drill pretty decent but don't let your drills get dull at all! I'd start at 375ish, your drill will self destruct in 420 nearly immediately at the edges of your drill flutes if you're going even a little too fast with the rpm's~

Are you drilling out vents in brake rotors by any chance?

WHATEVER you do, don't let that drill rub for even a split second or you'll screw yourself instantly!

How thick are the parts you're drilling?

One more comment... If you smoke a drill in a hole, DON'T try to redrill it with another drill, just get a center cutting carbide EM and plunge it out... Also, push that stupid drill right on through, don't baby it, you want to shove it right through! Just be careful when you break through the backside, like I said, that's the worst part by far...

[Clawsie Machine]

Thanks, JOBS DONE and Deliveried. Wasn't brke parts, just little parts for industry, got a drawing, material and off we went.

Here is what I found, It wasn't as bad as I thought it would be:

- Drilled 11/32 holes, 32 of them in 5/8's material and 16 in 2" material. Used a YG "jobber" plain "bright" drill, nothing special, 500 RPM's, 3 IPM feed, peck every .100", FULL FLOOD on coolant, never had to sharpen drill. 7/16 drill, same peck, feed @ 2.75", RPM seemed to like 415.

- Now milling, I used a Ceritzitit insert for SS/Titainium and Aluminium in a 1" Seco indexable holder, ONE INSERT. .050" depth of cut, 4000 RPM and 30 IMP. FLOOD COOLANT, Never even smokes a tip. Slotted 12 pieces 1/2 deep, 40 mm wide and profiled all 60 pieces and varies squaring of blocks. I did change the insert going into production just to be safe, but profiles/contuorerd all 60 piece and used this for both rough and finish process. GREAT finish.

- Not as much love for a 1/2" Ti coated carbide EM. Found for mine, FLOOD again, 1800 RPM and 15 IPM. .035" depth of cut. Ran OK but was a used and not new EM so I wrote it off as that.

Thanks, John and hope this helps others

[camcrazy]

I am drilling 420 Stavax and am using the same SFM (45) and a .008 IPR on a 17/32 cobalt drill with a .100 peck and am only getting about 8-12 holes before the drill breaks. I am drilling 2" deep. Would anyone recomend drilling a pilot hole? Or would that cause other problums? Any other recommendations?