Mortising on the Drill Press Lansing MI

Mortising on the Drill Press

Even though they're sexy, benchtop mortising machines aren't the onlypower-tool option when it comes to cutting square-shouldered mortises.A drill-press mortising attachment can be just as effective and itcosts a lot less: $30 to $80 instead of $200 or more. I'll show you howto tune any out-of-the-box mortising attachment so it's easy to installand a joy to use.

Mortising attachments are available for almost every drill press.Although they vary in appearance, they all have three basic components:a fence, a chisel holder and a hold-down. Upgrading these parts tostabilize the workpiece and operating the drill press at the optimalspeed are the keys to success.

I get first-class results with my tuned-up mortising attachment. Thatmeans I don't have to store a large, heavy mortiser that I would onlyuse occasionally. On the drill press, I can slow the speed way down,too, so I don't overheat my bits. Drill-press mortising is slower, butit's much more pleasant, a lot quieter and much less nerve-wrackingthan using a mortiser.

Square mortises require special bits, which can be bought individuallyor in sets. Bits range in price from $10 to more than $50 apiece.Inexpensive bits usually won't stay sharp as long (see "Start Sharp,Stay Sharp," page 5), but dropping one on the concrete floor won't giveyou a heart attack, either.


Two-piece mortising chisels cut square holes. The auger bit fits inside the chisel and protrudes slightly.

During operation, the augerdrills a round hole and the four-sided chisel squares the corners. Cutside by side, square holes create mortises (see photo below).1. Slow down.
Mortising chiselswork best at slow speeds, between 1,000 rpm and 1,500 rpm, depending onthe mortise size and the wood density. Within this range, use trial anderror to find the speed that works best. 2. Mount
the mortising fence ona separate base, rather than fastening it directly to the drill-presstable. Then clamp the base to the drill-press table. This setup makesthe fence easy to adjust, so positioning the workpiece is a breeze. 3. Install
the chisel and bit.The chisel holder, which clamps on to the quill, centers the chiseldirectly beneath the chuck. Lock the chisel with its collar tightlyagainst the holder. Then slide the bit into the chuck. 4. Leave
a gap. Position theauger bit with its cutting head about 1/16 in. away from the domedinside surface of the hollow chisel. Don't jam these two partstogether. This gap is essential, because it allows shavings cut by theauger to be lifted into the hollow chisel and ejected. If the gap istoo small or too large, the trapped shavings will bind the bit.5. Lubricate
the auger bit aftermaking sure it spins freely inside the chisel.

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