Essentials of woodworking

by Ira Samuel Griffith

Fig. 108.

A better way—the method a mechanic would use—is to test the edge by drawing the thumb along it lightly. [Fig. 108]. If the tool is sharp one can feel the edge “taking hold.” If dull, the thumb will slide along the edge as it would along the back of a knife blade.

Good judgment is necessary in this test or a cut on the thumb may be the result. No pressure is required, just a touch along the edge at various points.

What actually takes place is this: The cutting edge, if sharp, cuts the outer layer, the callous part of the ball of the thumb, just a little. The sense of feeling is so keen that the resulting friction, slight as it is, is transferred to the brain of the worker long before any injury need be done the thumb. If the tool is dull, no cut, hence no friction can result. Do not use the finger, as it is not calloused as is the thumb.

CHAPTER VI.
Form Work, Modeling.

58. Making a Cylinder.

—The cylinder is evolved from the square prism by increasing the number of sides until a prism is formed with so many sides that its surface can be easily transformed into a cylinder by means of sandpaper.

Fig. 109.

(1) Begin by making a square prism which shall have the same dimensions for its width and thickness as is desired for the diameter of the cylinder. (2) Change this square prism to a regular octagonal or eight-sided prism by planing off the four arrises. The gage lines which indicate the amount to be taken off of each arris are made by holding the gage block against each of the surfaces and gaging from each arris each way, two lines on each surface. These lines must be made lightly. The distance at which to set the spur of the gage from the head is equal to one-half the diagonal of the square end of the prism. [Fig. 109]. Since the ends are less likely to be accurate than any other part, it is advisable to get this distance as follows: Lay off two lines on the working face a distance apart equal to the width of the prism. These lines with the two arrises form a square the diagonal of which can be measured and one-half of it computed.