New machine zeroing trick with laser

I don't know if it is really new or not, but it is new to me.

While talking with one of our many happy customers who have
converted their CNC machines to DeskCNC control systems, the
conversation drifted to limit switches, fixture offsets and zero
setting on table based machines. Their method of finding a fixture
zero was interesting to me, and I thought I would share it with the
group.

They have installed a laser pointer onto the Z axis, aimed at the
table below the spindle. The laser pointer is offset somewhat from
the spindle centerline, so it stays mounted during machine
operation. They have placed a pin-hole aperture over the laser
pointer lens to reduce the size of the spot projected below.

The work holding fixture has a target hole made by driving a small
finishing nail into the wooden base, then removing the nail. To
zero the fixture, the laser pointer is turned on and jogged over the
hole. As the spot is positioned over the center of the hole, it
disappears. Moving the laser pointer, just a couple of thousandths
off the center of the hole and the spot reappears in that direction
of movement. This is apparently sensitive enough to provide the
fixture location with in a few thousandths of an inch(plenty good
for woodworking). It repeats reliably and permits fixture setting
without cutting tool contact or removal.

Any others incorporated/designed/used similar devices in your CNC
machines?

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Fred Smith
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