Then I got a piece of scrap wood to serve as a baseboard, and attached a
strip of wood at the back to serve as a guide. The idea is that the
tracker bar will slide along this guide, and this will keep all the holes
Now for the spacing: I attached the digital slide caliper to the baseboard,
making sure that the caliper was securely fastened in a position where it
could slide freely and extend the entire length of the row of holes. I
also made sure that the base/back board was firmly clamped to the drill press
platform and that all locking screws on the platform and column were securely
I drilled pilot holes using a 1/16 bit, lowering the bit very slowly
each time to prevent wandering caused by grain irregularities in the wood.
After the first hole was drilled, I zero set the caliper, selected
mm as the measurement, then proceeded with the rest of the holes.
With zero as the setting on the first hole, the row of
holes (from smallest pipe to largest) would have caliper readings of 0, 6,
12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78, 84, 90, and 96 for the small
holes, then 105, 114, and 123 for the larger holes. I tried to go for accuracy
within a range of +/- .05mm. Do not zero the calipers between each
hole, but measure off multiples of 6mm (9mm for the last 3 holes). This
avoids cumulative errors, and even if you make a mistake with one hole, the
holes after that won't be affected. As a check, the last hole should
After the pilot holes were drilled, I repeated the procedure with the final
4mm and 6mm bit drilling.
Upon Melvyns suggestion, I went with Walt Lysacks method of
construction rather than with John Smiths honeycombed cardboard method.
In a variation of Walts method, I started with a 7/8 thick,
solid piece of hardwood, drilled the 4mm and 6mm holes about 1/2 down
into the block, then sliced off the top 1/4 of the piece for the tracker