Problem- center drilling

[Pontiff51]

Hi all. I'm center drilling into 17-4 SS tubing, carbide tools chip and our regular KEO tooling will not last too long. Any other center drill material that anyone knows about?
Thanks in advance.

[Brepins]

hss s1200 z-.035 f6.

[beege]

Guhring makes some nice metric spot drills, cobalt. In any case, cobalt would be the way in 17-4. I never use center drills. Way too much time to get to a decent depth, and it was designed for parts that get ground between centers.

[Delw]

I've used KEO center drills for over 20 years, they work in just about anything even inconel 718 and in my Opinion are the best. you also mentioned Carbide and having problems, at this point I am going to say its the way your machining and not the material or the tooling used.

you didnt say what size KEO your using, where your drilling side of part top center line etc etc.

I would look for these things first, your spindle is junk or your using a hand drill, your holding the part by hand vs a vise or clamping it down, your drill chuck your using has way to much run out, your drilling on the side of the tubing in which case you need to end mill a small flat first. your speeds and feeds are way to fast.


if your drilling on the side use a endmill to spot the hole first, have the endmill mill a flat just a hair bigger than your center drill pilot.

Delw

[Mcgyver]

might not solve this particular problem, but if you are spot drilling, use a spot drill not a centre drill, centre drills are best left for making holes for lathe centres.

[BobWarfield]

FWIW, indexable spot drills are nifty tools. Use them to spot drill, chamfer, and I've even seen them used for engraving:

YouTube - NINE9 NC Spot Drill

YouTube - NINE9 NC Spot Drill

Cheers,

BW