Sine Bar

Sine Bar: A sine bar is used in conjunction with slip gauge blocks for precise angular measurement.  A sine bar is used either to measure an angle very accurately or face locate any work to a given angle.  Sine bars are made from a high chromium corrosion resistant steel, and is hardened, precision ground, and stabilized.

Two cylinders of equal diameter are placed at the ends of the bar.  The axes of these two cylinders are mutually parallel to each other, and are also parallel to, and at equal distance from, the upper surface of the sine bar.  Accuracy up to 0.01mm/m of length of the sine bar can be obtained.

A sine bar is generally used with slip gauge blocks.  The sine bar forms the hypotenuse of a right triangle, while the slip gauge blocks form the opposite side.  The height of the slip gauge block is found by multiplying the sine of the desired angle by the length of the sine bar:  H = L * sin(θ).

Primary use

1. Positioning precision angles

2. For mill, grinder, stenciling

4 steps

1. Locate tools:

Sine Bar : Cabinet 5

Gage Blocks : Cabinet 5

2. Calculate which gage block to use

Sine Bar is 5 inches center to center

Using calc take 5 * Sin ( θ ) this is the gage block or blocks that will be used.

3. Create triangle

Use Sine Bar as Hypotenuse

Using gauge blocks as height 

Construct a 90º triangle

4. Set-up machines

Using sine bar as a parallel bar set  work piece in mill clamps then remove sine bar and continue

Use sine bar set-up as a stencil on your work piece

Use sine bar as a plane for your work piece on the grinder.

SINE BAR PRINCIPLES

• The application of trigonometry applies to sine bar usage.
• A surface plate, sine bar, and slip gauges are used for the precise formation of an angle.
• It is possible to set up any angle ϴ by using the standard length of side AB, and calculating the height of side BC using BC = AB * sin(ϴ).
• The angle ϴ is given by ϴ = asin(BC/AB).
• Figure 1 shows a typical sine bar set up on a surface plate with slip gauge blocks of the required height BC to form a desired angle ϴ.

Uses the formula: G = C * Sin(A)

If you just want to set an angle with a sine bar and stack of blocks, then take the sine of the desired angle on your calculator and multiply the result by the distance between the centers of the cylinders in the sine bar. Assemble a stack of blocks equal to this value and put it under one of the cylinders.

Set up a 5.0” sine bar or sine plate to 30°

SIN (30˚) = 0.5000

0.5000 x 5.0″ (sine Bar Length) = 2.5000″

Round 2.5000″ to 4 Decimal Places = 2.5000″ Gage Block Height.

Sine bar consists of a precisely machined corrosion resistant chrome steel. It is essentially hardened and stabilized. The relief holes are drilled into the body of sine bar to reduce the weight, and to facilitate handling.