Fig. 2315.
Fig. 2316.
Fig. 2317.
Let it be required to make or test a piece of work such as in [Fig. 2314], the teeth to be equally spaced, of the same angle, and of equal height. A template must be made of one of the two forms shown in [Fig. 2315]. To begin with, take a piece of sheet metal equal in width to at least two teeth, and, assuming that the template is to have two teeth, file its sides p q, in [Fig. 2316], parallel, and make the width equal to twice the pitch of the teeth. We next divide its width into four equal parts by lines, and mark the height, as shown in [Fig. 2316]. If we desire to make the template such as at a, we cut out the shaded portion; or for the template at b, the shaded portion. It will be observed, however, that in template a there are two corners c and d to be filed out, while at b there is but one e, the latter being the easier to make, since the corners are the most difficult to file and keep true. The best method of producing such a corner is to grind the teeth off the convex side and at the edge of a half-round file, producing a sharper corner than the teeth possess, while giving at the same time a safe edge on the rounded side that will not cut one angle while the other is being filed. But when we come to apply these templates to the work, we shall find that a is the better of the two, because we can apply the square s, [Fig. 2317], to the outside of the template, and also to the edge f of the work, which cannot be done to the edges g of the work and h of the template, because the template edge overhangs. We can, however, apply a square s′ to the other edge of b, but this is not so convenient unless the tops of the teeth are level.
