In many cases it is necessary to test the relation of lines and surfaces which are not at right angles to each other. For this purpose a sliding bevel is used. The sliding bevel differs from the try square in having a movable blade. This blade may be set at any desired angle from 0 to 180 degrees. A locking screw secures the blade tight at any angle.
The sliding bevel is used for laying out angles other than 90 degrees and for testing constructed angles. The sliding bevel may be made entirely of steel or wood or it may have a stock of wood and a blade of steel.
There are various ways of setting the sliding bevel to the required angle.
Setting to a drafting triangle
Should the triangle used in drafting be available, angles of 30 degrees, 45 degrees and 60 degrees are easily obtained by adjusting the sliding bevel to the sides of the required angle.
Setting to a framing square
To set the bevel at a miter (an angle of 45 degrees), place the stock against one leg of the framing square and adjust the blade so that it will agree with equal distances on both legs, as 5cm and 5cm. Any distances may be taken, but it must be the same on both legs.
Setting to a protractor
Slacken the locking screw enough to allow the blade to be moved. Hold the stock against the base of the protractor, set the blade to the required angle and tighten the locking screw.
Testing constructed angle
To test a chamfer or bevel for trueness, set the sliding bevel to the required angle. Move the sliding bevel along the object to check more than one place.