Here I am going to show a way to use the height gauge, a combination square with center head and a flat surface to get the center of a circle.
I need to drill four holes evenly spaced dead center of the slots already in this four jaw chuck.
They need to be flush or just below the surface of the chuck so I will have to do what they call counter drill the holes.
I have already measured that and I have plenty of metal left over to do it.
I need to do this so I can mount it to the rotary table.
The height gauge has a carbide scribe on the end to etch little lines as you move it across the surface.
You run the gauge down to the flat surface and zero it.
You then measure the height of the object this being the chuck.
This was 6.294.
You dived 6.294 by 2 and get 3.147.
You set the compound square up on the slots like you see in the pictuer.
This sets the chuck where you want it to make the marks at 3.147 exactly in between the slots already there 90 degrees apart.
I could have just used the center head but this was more fun and accurate.
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Worth