"jim rozen" wrote in message
...
In article , Harold and Susan Vordos
says...

I, for one, do. Spiral point taps are intended to be power driven and
are
not easy to start by hand. They're prone to damaging the starting
threads
because they don't self align well, the way a taper tap does. .
There's
no better tap on the market as far as I'm concerned, but I also have a
Procunier tapping head.

Spiral point taps and two- or three- flute gun taps are not the same
thing however. Spiral point taps are designed to extract the chips
backwards out the hole in a continous cut. The gun taps are ground
to sling the chips forwards in the hole, and as such are best used
in through holes.

See Wayne's post. His comments are on the money.


I would not shy away from power tapping a hole like the OP mentioned
using a two flute gun tap. I've done stuff like that with nothing
more than a reversible, variable speed milwaukee hand drill.

That was my point. I suggested not power tapping with *hand* taps,
although I may not have made it clear. Straight flute taps without the
spiral point don't drive the chips in either direction, permitting them,
instead, to accumulate at the point of origin. If you don't back the tap
at least every half turn, quarter turn being preferred, they don't fall
away, eventually packing up enough to jamb the tap. Thin material
presents the same problem, buy you're usually through the hole before the
tap has accumulated enough chips to jamb.


With a procunier head, it's dead easy.

But not with a *hand* tap.


I prefer two flute gun taps over regular hand taps any day, even
when tapping stuff by hand. The need to stop and clean out small
holes as the chips accumulate (if they cannot be through holes) is
not a terribly big deal as most of the stuff I do is not production,
it's one off.

I do too, but not when starting the tap. It's a no brainer once the tap
is started----I don't like fighting with the chips any more than anyone else
does. I use the typical gun tap for even blind hole tapping. It's easy
enough to remove the accumulated chips from the holes with a needle air
hose, which I keep at the ready. Rarely do I have problems removing them
unless I've tapped into them to the point of full compaction. Do keep in
mind that I've run parts in production, not just tooling.

I think most of the gun taps are simply higher quality than the
hand taps I see.

Very good observation. I have hand taps that are not ground threads, which,
today, boggles the mind. The process of making such tools is so easy by
grinding that I can't even imagine milling them, yet that was common
practice at one point in time. Good name brands, too-----such as
Greenfield.

I don't like hand taps, but I have them.

Harold