Depth Gage and Combination Square - 3: The Protractor Head
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WARNING: Machine tools present a safety hazard. Improper operation can result in severe injury. These topics are for non-laboratory study only and are not to be used in conjunction with the operation of any tool or machine described herein. Never use a machine tool without the supervision of a qualified instructor.
The protractor head is a versatile and useful tool for the measurement and layout of angles. It can be used alone or in combination with the channeled rule as shown (figure 1). The protractor head has a revolving turret with graduations from 0 degrees to 180 degrees on the turret and graduations that coincide with a reference mark on the protractor head (figure 2). The protractor can be revolved freely or locked in to the desired angle. A spirit level is built into head which makes it possible to lock the turret to an angle and check for parallelism or perpendicularity to a work surface (figure 3). Hold the protractor base firmly against the surface of the work piece or the surface plate and set the blade to the part's angle until no light is showing between the work piece and the blade. Lock the protractor and then read the angle.
Figure 1
Figure 2
Figure 3
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label: measurment, depth gage, combination square, protractor head, square, head, center head