Teeny Tiny Hole

[arobustus]

I have been asked to drill a .014 hole .1 deep. It starts at the bottom of a 1/8
NPT, and breaks out into a .156 hole .1 away like I said. Being designers they are insisting on the .1 length to "quiet" the air flow.
Material is a free machining brass forging alloy 377.
The part is now machined on an Mazak VQC-15 circa 1989 w/Mazatrol 32. On the good side, the machine is in excellent shape. This is a new feature intended to save money by eliminating an $8 bushing. Don't ask me. Note, the bushing was not formerly pressed into the part in question, it was somewhere else in the
assembly.
Any suggestions??
Thanx,
arobustus

[Chris Welton]

The smallest drill size even considered in the ANSI sandard is a #80 at .0135, and the second smallest is a #79 at .0145 in. Good Luck.
All for an $8 bushing.... jeesh

[psychomill]

.100 is a long way for a .014 drill. I'd use a carbide drill. I've drilled alot of micro holes (down to .0035) for air bearings.

I like and recommend Sphinx Drills which is now owned by Big Kaiser. There are others though. Take a look at page 6 (Spirec drills). HSS on pg 7 and carbide on Pg 8. You can get a .36 mm drill which is just tad over .014. It has a 2.4mm LOC which is about .0944 deep. You're real close. Might be close enough to get lucky.

Be sure to use tons and tons of coolant, short pecks, and I hope you have gobs of RPM. The critical thing for tool life,...... RUNOUT!!!! Be sure this thing is spinning as "dead zero" as you can get it. Don't spot the hole (the NPT hole is plenty). And I would recommend you write a drill macro for it since you're inside of another hole. With these drills, its good to back completely out of the top even to clear chips and the "fines" in the coolant that may be stuck in the hole.

Good luck...

[Chuck Pressure]

I totally agree with Psychomill.....only I might try cobalt or coated instead of carbide....I just did a job with a .0156 hole .060 deep in a-2 tool steel.....guhring TIN coated worked excellent, I got over 40 parts on 1 drill! You gotta indicate centerline!
Psychomill, why not use a spot or a double ought c-drill???

[sendkeys]

in my last few orders most the time i get a couple carbide #80 and 79's in the "micro drill bit sets" from hf
(http://www.harborfreight.com/cpi/cta...emnumber=34640)

Not sure how many parts you're making but just a idea