[foil25]

Hi,

I'm working on a project for a friend and we have to drill blind holes in stainless steel .1015-.1020 wide by .25 deep. So we're using a HSS drill at 2,365 RPM and feed of 10 IPM. The drill we are using holds the tight dimension in AL 6061 but when we drill stainless it comes out .102+ (it's out of spec). Thanks.

Assumptions:
All dimensions are in imperial units.
We're using a HAAS Super Mini Mill milling machine.
The stainless has a cutting speed of 60 ft/min.
CNC G-code calls for G81 basic drilling canned cycle (not peck drilling).
HSS drill is not wearing out or causing problems.

[Geof]

Maybe someone will contradict me but I think expecting to hold a 0.0005" tolerance on a drilled hole is completely unrealistic. If you are able to get this on aluminum you are very lucky.

[MrWild]

Try this, Stone a radius on the tip of the drill flute. It doesn't have to be much. no more than .020 radius. Your drill will cut more like a ream then. Make sure the radius keeps the rake/relief of the dutter. You don't want the part to rub on the flute, you want the radius to be part of the cutting action. Use a profilometer to make sure the radiuses match fairly well. It still may not pull the tight tolerences that you need, but it may work. It has for me in non-production settings.

[dertsap]

.0005 is do-able with decent quality carbides , probably the only way you could accomplish it with hss on stainless is to predrill with a bit smaller of a drill first then feed your next drill in with a heavy chip load so it doesn 't have a chance to wander ,more or less plunge it as you would a reamer

[cam1]

Tried tested and true:
Center drill, drill undersize, ream. This works every time. For higher "production", another method may be more suitable.

regards

[foil25]

I appreciate all of the suggestions. I'll try some of this stuff on Friday when I get back to working on the project. Thanks for the support!