In Tricks of the Trade

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From top left to right: Carriage bolt #1, Hardwood arm, Carriage bolt #2, Paper feeler gauge.

How do you know if the table on your drill press is square? Not more-or-less square, but precisely square?

I’ve adopted an old machinist’s trick, using a very simple jig. To make it, you’ll need a hardwood arm, two 5/16″ carriage bolts that are 2″-3″ long, four nuts and four washers.

First, make the arm. Mine is about 3/4″ x 1″ x 6″, but the dimensions aren’t critical. Drill 5/16″ holes 1″ in from each end.

Cut off the head of carriage bolt #1. Slip it through one of the holes and fasten it with two nuts and two washers. Insert bolt #2 in the other hole, as shown in the photo. Fasten it with nuts and washers. 

To use the jig, insert bolt #1 in the drill press and tighten the chuck. Place a piece of paper on the table, then lower the quill until bolt #2 just touches the paper. Lock the quill.  Fine-tune the bolt’s height, if necessary, by loosening its nuts; then turn the bolt with a wrench.

Rotate the chuck—by hand—so the arm points to the other side of the table. Try sliding the piece of paper under the head of the bolt, using the paper like a feeler gauge. Adjust the table’s tilt until you can “feel” the bolt with the arm pointed both ways.   –John Cusimano

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