On Sunday 03 November 2013 18:04:07 Jon Elson did opine:
> Gene Heskett wrote:
> > Now if someone knows where I can buy an 8-32 tap that can tap an 8-32
> > blind hole pre-drilled .250" deeper than the needed threads, tapped
> > as deep as the tap is long and do it repeatedly for a dozen holes
> > before I am rigging to EDM its broken pieces out of the hole, I am
> > all ears. And it may have to do it in a piece of tool steel right
> > out of the paper sleeve.
>
> I buy 5 or so at a time from MSC, J&L, KBC and similar outfits.
I've been getting normal mills from Hemly, and circuit board stuffs from
MCS, Midwest Circuit Specialties. Hemly's choices aren't so broad, but the
prices are tolerable. MCS has nearly everything in pcb stuff but the
engraving bit, and I've forgotten where I got a 5 pack of those, chipped
the first one right away, but the 2nd one has now made about 20 smallish
boards.
> For shallow holes or thin sheet material, I use spiral FLUTE taps,
> they bring the chips up the hole just like a twist drill. Fantastic!
> But, on deep holes, they will bind up with chips and break sometimes.
So will drill bits, so we're back to a peck cycle. There is probably an
ideal feed/rev rate that I am usually under so my chip strips are too small
& breakable=premature clogging. AKA thats my fault. Usually my caution is
related to the plastic gears in the mill head. I have stripped the hubs
out of several already. The thought has crossed my mind to make a whole
new head, but I've miss laid my round tuit.
> So, for those I often use spiral point taps. I did a fixture plate in
> 3/8" aluminum with 288 10-32 holes in one setup, with rigid tapping.
> The tap is still about as sharp as when new!
Now that I'd call outstanding. What do you use for cutting oil in alu? I
get the impression the ACE Hdwe stuff I buy by the qt, isn't near as oxygen
proof as a mist of safflower oil. But my mister uses way too much oil &
turns the shop into a fog bank I can't see the 16' length of, & takes
washing my glasses with several concoctions to make them truly useful
again.
Thanks Jon.
Cheers, Gene
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
In the next world, you're on your own.
A pen in the hand of this president is far more
dangerous than 200 million guns in the hands of
law-abiding citizens.
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