Grazes the surface that is :

Martin H. Eastburn wrote:
The idea is to sweep a circle having a common center point and length.
If it grases the surface in a circle - turning by hand - if it digs in -
that side is high....

It is simply a single rod that is bent off center to sweep a circle.

Martin

dpb wrote:
Phisherman wrote:
...
For testing drill press runout you can, with the power cord unplugged,
use a coat hanger chucked in the drill press such that it lightly
touches the drill press table top. When it is even all the way
around, the spindle is perpendicular to the table top. No special
tools needed!

??? I've never seen a precision-enough coat hanger that any part of
it would be straight/level enough in reference to any other that it
would be of any use as a measuring tool...

How does this work, exactly, again?????

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