Can I Use a Mortise Bit in a Drill Press? Here Is the Honest Answer

You have a bag of mortising chisels, a drill press in the corner, and a nagging question: can these two things work together, or do you need to buy yet another machine? It is a fair question, and the internet gives muddy answers. The honest one is yes, with a specific condition. You cannot just chuck a mortise bit and go. You need the right attachment, and your press has to be on the list of machines that attachment fits.

A mortise bit, a hollow square chisel with a drill bit inside it, cuts square holes for joinery. A drill press can drive one, but only through a mortising attachment that clamps the chisel to the quill and adds a fence. The attachment is the missing link. Without it, a mortise bit and a drill press do not connect.

Short answer: yes, you can use a mortise bit in a drill press if you add a mortising attachment that fits your machine. A kit like the Grizzly H7789 lists the exact presses it fits, and if yours is on that list, you are set. If it is not, the attachment will not clamp your quill properly.

Yes, but only with the right attachment

The drill press supplies the downward plunge and the power. The attachment supplies everything else: a holder that clamps the hollow chisel to the quill, a fence to register the work, and often a hold-down. The drill bit goes in the chuck, the chisel sits in the holder around it, and together they chop square holes.

So the real question is not “can a drill press do it” but “does an attachment fit my drill press.” That is a compatibility list, not a maybe.

Fit is a published list, not a guess

Mortising attachment kits publish which presses they fit, because the chisel holder has to clamp a specific quill diameter and the fence has to anchor to the column or table. The Grizzly H7789 kit, for example, ships with a column collar and a G9716 adapter and lists compatible machines including the Grizzly G0485, G0491, G7943, G7944, G7947, and G7948, the Shop Fox W1680 and M1039, the Delta 11-990 and 17-900, and the JET JDP-17M.

If your press is on a list like that, buy with confidence. If it is not, measure your quill and column against the kit’s requirements before spending, because an attachment that will not clamp your quill is just a box of parts.

What to expect once it fits

With a compatible attachment, set the drill bit slightly ahead of a sharp chisel, square the chisel to the fence, clamp the work, and chop overlapping plunges, cleaning the thin walls afterward.

The honest limitation: a drill press quill is built for downward thrust, not the sideways racking a chisel puts on it. Push too hard, especially in hardwood, and the quill flexes and the mortise drifts. Keep the chisel sharp, the pace moderate, and let it cool if it smokes.

Attachment on a drill press versus a dedicated mortiser

Against a dedicated mortiser, the drill press plus attachment wins on not buying another machine, and loses on rigidity and speed. The standalone tool has a stouter quill and a longer lever, so it chops faster and stays square under load. For occasional joinery, the attachment route is sensible; for heavy or daily mortising, the dedicated machine wins. You can compare a drill press mortising attachment and a mortising chisel set to get started.

Setting it up

1. Confirm your press is on the attachment’s compatibility list, or measure the quill and column to match.
2. Clamp the chisel holder to the quill and anchor the fence.
3. Set the bit slightly ahead of a sharp chisel and square the chisel to the fence.
4. Clamp the work with a hold-down or a 4-inch drill press vise and chop overlapping plunges, then clean the walls.
5. Keep the pace moderate, wear eye protection, and stay clear of the chuck, per CCOHS.

Who should read this

If your press is on a kit’s compatibility list, the answer is a clear yes, buy the attachment and go. If your press is not listed and you cannot match the quill and column, either find a kit that fits or use a dedicated mortiser instead.

Bottom line

Can you use a mortise bit in a drill press? Yes, with a mortising attachment that fits your specific machine. Check the kit’s compatibility list, like the one for the Grizzly H7789, before buying. Get the fit right, keep the chisel sharp, and cut at a moderate pace, and your drill press will chop real joinery.

• Yes, but only through a mortising attachment, not the bit alone.
• Fit is a published compatibility list; confirm your press is on it.
• Keep the chisel sharp and the pace moderate; the quill dislikes side load.

FAQ

Can I use a mortise bit in a drill press? Yes, if you add a mortising attachment that fits your machine. The bit alone will not connect; the attachment clamps the chisel to the quill.

How do I know an attachment fits my press? Kits publish a compatibility list. The Grizzly H7789, for instance, names the specific presses it fits. If yours is listed, it fits.

What if my press is not on the list? Measure your quill diameter and column against the kit’s requirements. If they do not match, find a kit that fits or use a dedicated mortiser.

Do I need special chisels? You need hollow square mortising chisels sized to your joinery, plus the drill bit that runs inside each one, usually sold together.

Why does my mortise drift out of square? Usually too much pressure flexing the quill, or a dull chisel. Sharpen the chisel and cut at a moderate pace.

Is a drill press as good as a dedicated mortiser? For occasional joinery, it is fine with the right attachment. For heavy or daily mortising, a dedicated mortiser is faster and more rigid.

References

• Grizzly H7789 Mortising Attachment Kit: https://www.grizzly.com/products/grizzly-mortising-attachment-kit-for-drill-presses/h7789
• TEKTON 4-Inch Drill Press Vise Manual: https://media.tekton.com/manuals/manual_53994.pdf
• CCOHS, Metalworking Machines - Drill Presses: https://www.ccohs.ca/oshanswers/safety_haz/metalworking/drillpresses.html