Drill Accurate Holes Without Blue Tape
For many years I’ve wished for a better way to drill holes to an accurate depth without putting blue tape on the bit. The tape slips. Always. And then disaster ensues.
I’ve tried all manner of gizmos that clamp to the bit, but they are only barely better than blue tape and they are useless when it comes to drilling holes at angles, which is what I do all day long.
Today when I was drilling compound-angles in a chair, my blue tape slipped after the third mortise. I caught the problem before I made the next hole – thank goodness – but I was a little miffed.
At that moment, it occurred to me that I always drill mortises to a 1” depth with this spade bit. So I could make the depth stop a permanent addition to the bit. So I walked over to the bench grinder and made two notches in the spade bit at exactly 1” from the bottom of the bit’s spurs.
It worked brilliantly.
Feeling cocky, I took some red permanent marker and colored the inside of the notches to see if that would improve visibility. It didn’t. Oh well.
Spade bits are the unsung hero of the woodshop. When sharp, they drill accurate holes at compound angles without complaint. They are cheap – about $2 to $4 each. They don’t clog. And they can be easily modified to be any dimension you like. In the bit shown here I ground off about .010” off the edges to make my holes slightly undersized. That makes my spindles fit tighter.
If you’d like to make the jump to spade bits, avoid the ones with a threaded lead screw. These will pull your bit into the work at an uncontrollable rate of speed. The trick to getting a clean hole with a spade bit is to run the drill up to full speed before easing into the work.
And save your blue tape for the 4,045 other uses in the shop.
— Christopher Schwarz