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 Aug1924. 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!