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set two angles, for this a compound sine plate is used.

35.6.7.1 - Sine Bar Limitations

•When using a sine bar, the height setting is limited by the gauge block divisions available (often 0.0001”). This results in an error that may be negligible, or in some cases quite significant.

•A simple example to illustrate this effect is given below for two extreme cases. In the first case the sine bar is near horizontal, in the second case it is near vertical. Assuming a sine bar with 10” centres, and two angles of 1°-30’ and 88°-00’, and that an 84 piece gauge block set is used.

Therefore, as the angle approaches 90°, the error increases

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Next, find the gauge block heights,

******* DO IN CLASS

Given the actual heights, we can recalculate the actual angle of the sine bar,

***Note: the error for the larger angle is also much larger

• In any of these cases we can see that at larger angles, the sine bar is susceptible to errors in the length of the sine bar, as well as in the height of the gauge blocks.

35.6.7.1.1 - Practice Problems

1.Determine what height is required to set up a 5” sine bar for an angle of 11°34’. Specify the gauge block stack required.

2.Why are different grades of gauge blocks used?

ans. There are different quality levels for gages blocks. The poorest sets are workshop grade and are more accurate than most machine tools. The best sets are very accurate, and must be kept in tightly controlled conditions. The bast sets are used for calibrating others.

3. How are a ring gauge and a plug gauge different?

ans. A plug gage goes into a hole, a ring gage surrounds a dimension.