PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
(9) Sine Bar.
(a) General. A sine bar (figure 24) is a precision tool used to
establish angles which require extremely close accuracy.
When used in
conjunction with a surface plate and gage blocks, angles are accurate to
within 1 minute (1/60). The sine bar may be used to measure angles on a
workpiece and to lay out an angle on the workpiece that is to be machined.
Work may be mounted directly to the sine bar for machining. The cylindrical
rolls and the parallel bar, which make up the sine bar, are all precision
ground and accurately positioned to permit such close measurements.
scratches, nicks, or other damage should be repaired before the sine bar is
used, and care must be exercised in using and storing the sine bar.
1 A sine bar is a precisely machined tool steel bar used in
conjunction with two steel cylinders. In the type shown in figure 25 on the
following page, the cylinders establish a precise distance of either 5
inches or 10 inches from the center of one to the center of the other,
depending upon the model used.
The bar itself has accurately machined
parallel sides. The axes of the two