Re: Interpolating a blind hole for tapping





BottleBob wrote:

Fastest? Minimize tool changes?

You could always try a "Thriller".

http://www.turchan.com/thriller_more.html

PV:

Whether you drill, or helix in, you still should put a chamfer on the top of the hole BEFORE you thread it, so you don't fold any chips over into the threaded hole. Another tool change though for the chamfer. At least you'd be eliminating the drill tool change if you helix in.

Personally, I'd helix in with a minimum 3/8" dia. two flute end mill at 7,500 RPM (assuming this is alum.). Then thread mill. Thread mills aren't cheap though.

If you use a tap are you going to use a cut tap or a form tap? Cut taps will push the chips ahead of it and could cram them in the bottom of the blind hole and make picking them out a pita (paper clip with a hook on the end). It could also break the tap if you don't have sufficient clearance.
A form tap will require a larger starting hole diameter or you could seize the tap.


--
BottleBob
http://home.earthlink.net/~bottlbob

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