Page:Popular Science Monthly Volume 92.djvu/307

 Tricks of the Trade

Under this head each month there will appear one or more articles describing methods and short cuts in shop work practice

��Burning Holes in Patterns

PATTERN makers and other wood workers are often at their wits end to find a way to make smooth, tapering holes, especially in a piece of wood which is cross-grained, or in which the hole has to run diagonally with the grain. Ordinarily a sharp taper reamer may do the work, but one of just the right size, is

�����Tapered holes accurately sized by burning with wood points rapidly revolved in them

not always at hand, and when a hole of a particular size and bevel is required, the taper reamer will not do the work.

On a job recently, there had to be five smooth holes, of the same size and bevel, through a piece of ^-in. white- wood. The holes were ^ in. at the small end, and 1 in. at the large end. They were bored with a sharp bit, a little smaller than they were to be at the small end, then beveled with a sharp knife to nearly the size at the large end. A piece of hard wood was then turned to nearly the size and taper re- quired, as shown at A. This was revolved at medium speed in each hole until it burned a little. Care was taken not to let it burn too much. This was repeated until the holes were almost the size and bevel required. Next, another plug B was turned the exact size the holes

��were to be when finished. Then the holes were carefully finished with this. It is a good plan to turn a shoulder on the finishing plug so that the holes may be just alike. Finish the holes with fine sandpaper. — C. E. Stone.

Tempering a Chisel to Cut Stone or Bricks

A CHISEL to cut stone masonry work must be tempered to a different degree of hardness than those to use for other work. Before tempering, it should be sharpened on an emery wheel, as tempering puts a hard surface, or a sort of skin, on the cutting edge, which grind- ing removes to a certain extent, no matter how carefully the grinding is done. In grinding stone cutting tools, do not grind the cutting edge with too narrow an angle, but allow the edge to have an angle of over 100 deg. This gives a sufficient amount of metal back of the sharp edge, to enable it to withstand the shock of the blows. Too sharp an angle on the tool edge would cause it to break at the first blow. After the grinding is done, put the chisel into the fire and heat it to a cherry-red color, then dip the point of it into cold water — holding the chisel in a vertical position. Do not dip it all in, but leave some heat in the shank. Quickly brighten the point with a file or emery cloth and watch the colors closely as they travel down to the point. When a light-blue is reached, dip the entire chisel into cold water. It is then ready to use. — W. S. Standiford.

��Mercury Used for a Thrust Bearing on an Upright Shaft

ANEW bearing is being used on a generator set, wherein the main shaft stands vertically and supports con- siderable weight. Instead of being sup- ported by collars or an end thrust bearing, a small quantity of mercury is placed in a pocket at the lower end of the shaft.

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