Sine Bar

Primary Use
The primary use of a Sine Bar is to position the part being machined at a precision angle. Determining and setting up a part at the proper angle is crucial when using a mill or a grinder, or even just stenciling a line on the face of a part. The Sine Bar is used in conjunction with gage blocks and/or a spirit level. Gage blocks are just block pieces of metal that are cut to extremely precise lengths and usually come in a large set with many different sizes.

Step 1
Step one of the sine bar procedure is locating the proper tools that are necessary. The Sine Bar itself is located in Cabinet 5 while the Gage Blocks are located a drawer down in the same cabinet.

Step 2
Calculate and determine which gage blocks are going to be used in the procedure. The particular Sine Bar that the machine shop has is exactly 5 inches from center to center of the cylinders on the bottom. If the height of the part is know you can use the calculation 5*Sin(ϴ) which will give you the height that needs to be obtained with the gage blocks. If the height is unknown then various blocks can be stacked until the top surface of the Sine Bar is perfectly level according to a spirit level.

Step 3
Using the Sine Bar as the hypotenuse, create a 90° triangle.

Then stack up the gage blocks under the lower end of the Sine Bar so that it makes a perfectly level surface.

Step 4
Now that the exact height of the part is determined, the sine bar can be used to determine angle that necessary during the machining process. It can be used as a stencil on a part as well as a reference plane when using a grinder. A Sine Bar can also be used as a parallel when attempting to clamp a part into a mill clamp at a precise angle.