Rebarreling and Home-Shop Machining

First clamp a true edge to the toolpost and set the edge to run true by rotating the tool post and then going back and forth with the compound rest feed until the indicator reads 0 travel. Check both sides of the compound rest first, they may be true. Mine was not. (Photo 1 & 2).

Using a Dial, Vernier, or adjustable Protractor

I had recently purchased a used Browne and Sharp Dial Gauge Protractor. Seems to be a rare beast. I set it to 30.00 degrees. You could use a vernier protractor (or your good quality combination square protractor good for about .25 degree accuracy). ThenI mounted an indicator to an arbor on the milling spindle and contacted the edge of the protractor that was parallel to bed ways ( Photo 3). I adjusted the compound rest angle until the indicator showed no movement when moving the main lead screw feed wheel. The degree marks on the compound rest itself were about 2 degrees off. The angle is now set to grind a 60 degree center.

Using Dial Indicators and Some Trigonometry

Second method. I wanted to check the Brown & Sharp Protractor since I bought it used. I set up two indicators. One indicated the carriage travel along the bed. A second indicated the surface that ran true with the compound rest travel (Photo 4). I used set of indicators, matched by brand. I used the main leadscrew to move the carriage exactly 1.0000 inch. The other indicator indicated exactly .5000 inch. Perfect. That=s what you should get for a 30 degree angle. The used protractor is OK.

The trig and algebra that can be used for a different angle are in Photo 5.

For a 30 degree angle adjust the compound rest angle until the compound rest indicator moves .5 inch for 1 inch of carriage travel along the bed ways.

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