"Aribert" wrote in message
om...
Last week I went to a local machinery auction and for once there were
more lots than interested bidders. I bid and won a bench grinder for
$5, the auctioneer included the two prior lots that did not sell for
$5. One of those two lots consisted of an antique tapping head. The
brand name is ETTCO, Eastern Tube & Tool Co. w/ a patent lable of Aug
1924. I have never used a tapping head before - I have occasionaly
tapped using my Bridgeport w/ a tap in a collet. In playing with the
tapping head by hand, I have been able to make it reverse direction
but I am unsure of exactly what makes it change direction - is it
torque based or is it when the unit receives an axial load (tap
botomed out)? Do tapping heads typically have any adjustments? THere
are a couple of set screws that might be intended for ajustment but
there are no markings on the body nor any indication that there has
been frequent adjustments made to these set screws.

BTW, a mini gloat. I had 6 winning bids, all of them bottom feeder
types for odd lots. One of them was for a box or boring bars for $5
(there was only one bar in teh lot that I could use on my 12x36
Clausing. I resold the boring bars the next day. As I was loading
stuff into my vehicle to the people that bought the huge Monach lathe
for $100 (no joke!) came by and offered me $30. I bought a lot of misc
electical for $5. The lot consisted mostly dirty extension cords.
Under the pile of cords was a small, 1.2A Dumore hand grinder - that
works good!

Without being familiar with that particular tapping head, I'm not sure there
are any direct answers. Some tapping heads rely on the operator to not
break taps, others have adjustments that limit driving force. As has
already been suggested, when tapping, all you have to do is lift up on the
quill feed handle and the tapping head reverses, usually at a greater speed
than the tapping speed, so you can get out of a hole very quickly. Best
way to learn how to use yours if you have no literature on which to call for
information is to get your hands dirty on a practice piece that has little
to no value to you. You'll probably find you can still break taps, it just
makes it faster to do so. g

Make sure you use taps intended to be power driven. The typical hand tap
will usually lead to nothing but broken taps because they rely on reversal
constantly to break the chips. Nothing taps quite as well as a gun tap,
even in blind holes. Just make sure you have enough depth of hole to
accommodate the chip, which can usually be removed after tapping by using a
needle in an air hose nozzle. I keep several sizes of them in my toolbox
for just such an occasion. It's also a good idea to use only sharp taps.
Once they are dull, they usually lead to trouble, and are difficult to
re-sharpen with good results. Most attempts generally fail miserably.

Harold