I've never seen one in person--only pictures. My best guess is that
it's a clutch and a reverser gear to spin the tap in with the spindle
driving it and then twirl it back out after a pre-set depth. How close
On my Procunier the shaft fits in the drill press spindle and a rod against
the column keeps the body from spinning.
Inside are two bell shaped steel pieces with a donut shaped friction plate
between them. The shaft drives the upper bell , the friction plate drives
the tap and the lower bell is coupled to the upper bell by planetary gears
that turn it in reverse and at twice the speed of the upper bell
When you push down, the pressure on the tap pushes the friction plate up to
be driven by the upper bell. Forward and at the same speed as the drill
When you release the pressure, the friction plate spins free and the tap
When you lift up, the friction plate is pulled down and is driven by the
lower bell. Reverse and twice the drill press speed, unscrewing the tap.
Paul K. Dickman
B.B. wrote in message ...
Whatever you do, don't buy one of those Procunier widgets
because you'll find yourself tapping twice the number of
holes in about 1/3 the usual time, and what's worse, the
tap manufacturers lose a customer because you'll never
bust any taps any more.
Tapmatic type tapping heads work differently than the Procunier type.
I use both types in my shop. The tapmatics I use have an adjustable
clutch so the torque can be set for different size taps. They also
self feed a certain amount so that some shallow holes can be a
problem. And even though I set a stop on the quill the Tapmatics will
thread to slightly different depths. The Procuniers do not self feed.
It is easy to hold thread depth to +/- .003". The more pressure you
apply the more torque delivered to the tap. This can lead to tap
breakage if you're not used to using them. And really only on the
small taps. But I've tapped lots and lots of 00-96 threads in aluminum
with a 60 year old procunier tapping head. Most of the time I prefer
the Procunier head but the tapmatics seem to run a little cooler when
run at maximum speed and lots of holes. So the production tapping
usually gets the Tapmatic.