On Wed, 14 Mar 2012 15:05:27 -0500, Jon Elson wrote:

Spehro Pefhany wrote:


Looking at using some relatively small screws tapped into (probably)
6061 aluminum. Through holes, maybe 0.08" of material. Is it insanity
to think about using a cordless hand drill and run them right through
without backing off (assuming a good quality coated tap and aluminum
cutting fluid)?
I tapped quite a bit of 2-56 in 6061 using Alum-Tap fluid on a CNC with
rigid tapping. I used some $8 spiral-point taps to push the chips
ahead. The CNC guaranteed alignment straight over the hole.

There is a limit to how deep the hole can be for any particular tap
size, or the chips start to pack up and that's when you break the taps.
The tap manufacturer should have data on that.

The smaller the tap, the more critical the alignment parallel to the
hole becomes.

SmallParts used to (maybe still does) sell some magic wax that you put
down a blind hole, then tapped. The idea was that as you tapped the wax
would be deformed and push up the tap flutes, taking the chips with it.

Cool (and expensive) as all get out. I have no idea how well it works,
or if it's available in #0.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com