Page:Popular Science Monthly Volume 92.djvu/801

 Tricks of the Trade

A simple means of driving taps by power and a small vise for the work bench

��Homemade Power Tapping Machine for Rapid Work

AS it was necessary to tap several xV thousand 34-in. holes in many cast iron fittings some means of driving the tap had to be provided. There was no tapping machine in the small shop, but

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��Opposite revolving pulleys drive the tap in either direction according to the pressure

the foreman was equal to the occasion and quickly made the tap driver shown in the illustration. The shaft was made from a piece of steel tube about 6 in. long and ^4 in. outside diameter. Two wood pulleys were fitted to this shaft, one on each side of the bearing or support. One of the pulleys was turned to 3 in, in diameter and the other to a 2-in. diameter. A countersunk washer was fitted into the two outside faces of these two wheels and the edges of the pipe were beaded out to prevent them from slipping off.

Before attaching the pulleys, a piece of cold rolled shafting ^^ in. in diameter was centrally babbited into the tube. This shaft was then provided mth a central hole at one end to accommodate a tap, which was secured with a grub screw set into a slight depression ground into the tap shank. The shaft is provided with a carrier or dog at each end as shown. These dogs engage with the pins fitted into the outside surfaces of the pulleys.

The shaft is arranged to slide axially inside the tube, the amount of the sliding motion being so proportioned that when one set of pins engages one of the dogs,

��the other set of pins is disengaged.

The smaller pulley was used to drive forward and the larger one for backing up. It will be seen that on pressing the work on the tap, the shaft is pushed back and so engages the pins at the front of the machine on the small pulley. Pulling outward on the work draws the shaft out and thus disengages itself from the pins on the small wheel and immediately en- gages with those on the large wheel, which revolves in the opposite direction, backing the tap out of the piece.

The tube was held stationary in a wooden block fastened to the bench. One of the belts was crossed. The sur- faces of the pins where they engage were filed flat to make them act promptly. — John L. Allen.

��A Homemade Bench Vise for Small Work

THE illustration shows a cheap and quickly-made small vise for the model maker. It is suitable for any medium and light work. The vise is made from two pieces of band iron 1 }.4 in. wide and ^^ in. thick, with the jaw A bent as

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��Two pieces of metal and a cap screw with guide pin makes a model maker's vise

shown and the jaw B cut straight, with two holes drilled in it. The top hole is 13/16 in. in diameter and the one matching it in the top of the jaw A is ^ in. in

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