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Mortise kit for a Drill Press

A religious war

©2003 by Charles A. Plesums, Austin, Texas, USA

A recent list on the Internet gave several ways of creating the mortise of a mortise and tenon joint

  1. Mortise and Tenon machine
  2. Dedicated mortising machine, with saw cut tenons
  3. Drill Press with mortising attachment
  4. Router the mortise, square the mortise edges
  5. Router the mortise, round over the tenon edges
  6. Drill multiple holes, square up with chisel
  7. Hand cut entirely with a chisel.
  8. A mortiser with floating tenons (new addition to this list)

Yes, there is a machine that quickly makes matched mortise and tenon joints. Leigh has the FMT dedicated Frame Mortise and Tenon Machine for $800 plus a plunge router. Interesting. I have seen it in action a couple times. Outstanding mortises with perfectly matched tenons. Extraordinary at making joints at unusual angles, like chairs. Out of my league for occasional use, but something that was on my wish list for a long time.

I have cut mortises entirely by hand, or aided by drill or router. The results were barely adequate, and after cutting 8 mortises for one project, I had blisters on my hands. Not fun.

I now have a Delta drill press with Delta mortise attachment. It comes with three collars for various model Delta and Sears drill presses. Ridgid has a mortise attachment that looks identical, comes with four (rather than three) collars, and also fits the Delta and Sears drill presses. So it appears that Ridgid just added a suitable collar for the Ridgid drill press.

Recently I cut about 48 mortises for a dresser that I was building. Although I have never used a dedicated mortise machine for comparison, the mortise attachment on the drill press made it easy and the results were good - far better than my skill at manually squaring a hole started with a drill or router.

A lot of the argument against the mortising attachment to the drill press is the setup time. It takes me about 15 minutes to set up the drill press with the mortise attachment, but you can change the setup for different size/position in a minute or less. If you use the case that comes with the set, you must disassemble the unit completely to put it in the case properly, so the setup might be 30-60 minutes (as it was the first time I used it). To save time, I only partially disassemble the unit for storage. (I try not to let my opinion of the terrible plastic cases that come with many tools bias me against the tool.)

Be sure to check that the chisel is square to the fence each time you make ANY adjustment - movement of the fence is not constrained to be aligned with the chisel, and a chisel that is even slightly out of alignment will make a mess of the mortise. But aligning the chisel only takes a few seconds (losen one knob and hold a square along the fence and the side of the chisel).

Some people mention leverage as an issue. You are providing the muscle to cut the square hole with a chisel, while the drill is cleaning the scrap out of the center of that hole. Therefore you pull down hard on the drill press - far harder than when drilling. The dedicated mortise machines appear to have better leverage for this, but I haven't found the drill press to be a problem working with birch, walnut, maple, and poplar. A fairly fast stroke also helps clear the scrap out of the chisel, so it doesn't plug and overheat. (Ironically soft woods don't work as well as hard wood since the chisel tends to plug up with shavings more easily.)

The bottom of the mortise isn't too flat (but shouldn't be part of the supporting surface anyway). A round drill cleaning out a square hole leaves little mounds in the bottom corners, especially with hard woods. So I typically cut 1/8 inch deeper than required (measuring from when the chisel first touches the wood), and then do some minor cleanout with a hand chisel. Since the chisel/drill is the same as a dedicated mortise machine, I expect the results would be the same.

Bottom line, I bought a drill press, mortise attachment, and four bits for less than the cost of a dedicated mortise machine - in effect I got a free drill press in the process. And am very satisfied with the results.

Breaking News

I have gone to the dark side. Given up the traditional tools. I bought a monster MiniMax combo machine that includes a mortiser. I have sold the Delta mortise attachment, and now cut mortises on both legs and aprons, with floating tenons, using the MiniMax.

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©2003 by Charles A. Plesums, Austin, Texas USA. ALL RIGHTS RESERVED.