Figure 3 formulas. Of
course, if you own a
“high-tech” tiltable vise,
you have an even easier
The complete Parts List for the rotating center finder is
found in Figure 6.
The laser is a small 12 mm Die x 36 mm long module
that I bought from eBay vendor asab.design. These units
were spec’d for 5 mw of output power and were priced at
three for $12. There seem to be many sources that offer
compatible parts. Just be sure the unit you buy is
FOCUSABLE, has a DOT OUTPUT, and will run off of 3 VDC.
There is nothing particularly special about the battery
holders. I decided to use two single cell holders as opposed
to a two-cell unit as I wanted to distribute the battery mass
in a balanced way.
Figure 7 details the assembly of the three-point laser
mount. Almost any compression spring should work. I
started looking for something akin to a ball point pen
spring, but before I could find some pens to cannibalize, I
checked a “bag-o-springs” assortment that I had in my
shop. I found some small springs that were about . 2 in ID
and approximately 1/2 inch long (uncompressed)
that worked well.
If you can’t find a suitable spring in your
junk box or at a local hardware store, McMaster-Carr is a source to consider. The rest of the
hardware is garden variety machine screws.
Figure 8 shows a top view of the completed
assembly (wires not shown). The protruding 1/4-
20 machine screw is the shaft that goes into in
the drill press chuck/milling machine collet.
Figure 9 is a bottom view of the assembly.
BE SURE TO ADD TIE WRAPS TO KEEP THE
BATTERIES IN PLACE! The two hex head 4-40
screws in the LASER-COLLAR are used to align
This alignment device is powered by a pair of
AAA batteries. The batteries are symmetrically
mounted to the LASER_PLATE to keep the whole
assembly reasonably well balanced. The power switch is a
miniature toggle variety that is mounted through the
LASER_PLATE. The battery holder wires are routed through
the LASER_PLATE wire access holes, and then the holders
attach to the plate using 4-40 flat head or button head
Refer to the schematic and wire routing diagram shown
in Figure 10 to complete the wiring. Use minimal wire
lengths and heat shrink tubing to protect all splices. I also
suggest that you consider using some spots of glue (epoxy
or equivalent) to secure the wiring to the LASER_PLATE as
this will reduce the stress on the wires due to centripetal
force. The simple lasers that I used had just two power
supply wires with black = GND and red (usually) = +VDC.
Rotating Center Finder and
As you’d expect, safety glasses and other machine
SERVO 07/08.2018 41
Figure 11. Centering on the middle of a 1/4 inch square bar stock.
Figure 10. Alignment device schematic