Mortise Machine Mortises


I cannot imagine the number of mortise-and-tenon joints I’ve cut throughout the years. One of the pieces of furniture I’ve built numerous times, a Shaker Sewing Desk, has 55 of these joints. So, over the years I’ve developed an efficient process to cut a mortise.

No hand tools for me. I don’t have the time or the desire to do this work with a chisel and mallet. For me, it’s not the process of building the furniture, it’s the completed piece of furniture I strive for. I use a dedicated mortise machine.

I began woodworking with a bench-top mortiser. In fact, I wore out two machines before purchasing a Powermatic 719A, the old model without a tilting head. The 719A is available as a Jet JFM-5, although it’s white and not gold  (click here to read a blog entry about this machine).

With any mortise machine, the steps I take to a completed mortise are the same. The first step is layout and tool setup. The method I use most often is to find the center of my stock, then I align the point of the bit to that line. I turn the machine on as I dial-in this adjustment. The points on these bits are sometimes slightly off center. When the machine is running, the turning point becomes apparent.

After setup, make a series of plunges to cut your slot. Then make sure to reverse the stock and make a second run at the mortise. That guarantees the mortise is centered; even with accurate setup, it’s possible to be off a minuscule amount and that can have an impact on your work. If you’ve ever had doors that gently twist from top to bottom, not centering your mortise may be the cause.

I use a different setup for wider mortises. For these I position the chisel a measured amount off the machine’s fence. Make a series of cuts to form one side of the mortise, then reverse the stock and make a second series to create the slot. Again, I know the mortise is centered and equally spaced from the edges of my workpiece. Any additional waste remaining at the center is removed in another pass.

While setup is important, what I find most interesting are the results from the actual cutting of the mortises. The photo at the top of the page is a completed mortise. It differs from the photo directly above due to an extra step in the mortising process.

If you cut the mortise in a single pass, the slot is created, but the amount of waste remaining in the mortise is substantial. To complete the mortise and leave it clean and nearly waste-free, take a second run in the slot. However, on this pass forget trying to remove as much waste as possible with each plunge and take baby steps. The extra pass is quick and the result is a cleaner, ready-to-go mortise.

– Glen D. Huey

Looking for More Free Woodworking Information?
– Sign up for our newsletters to get free plans, techniques and reviews HERE.
– Like tools? We do! Read our latest tool coverage HERE.
– Looking for free project plans? We have hundreds. Click HERE.
– Learn a new woodworking technique today. Click HERE.
– Want more videos? See all our free videos HERE.

8 thoughts on “Mortise Machine Mortises

  1. Neil

    Hi Glen……recently took a furniture road-trip with a very talented young woodworker. He specifically mentioned wanting to see more of Glen Huey. Personally I like reading lines like this:

    "it’s not the process of building the furniture, it’s the completed piece of furniture I strive for."

    Also, your recent podcast interview with an experienced woodworker was very important.

    Thanks……..Neil

  2. glen

    Chuck,
    We’re a big fan of the step method for chopping mortises – create one square hole, then skip the second area and plunge the third, etc. – this keeps pressure on opposite faces of the chisel. In other words, on the first run of cuts, the wood is present on all four sides of the chisel. Then when you return to chop out the waste left between the holes, the wood is on the two opposing sides, with no wood present on the remaining sides. That keeps the chisel from deflecting as you chop.

    Due to most of my mortises being 1/4", I work this method most of the time. If I’m using larger mortise chisels, 1/2" or larger, I step through the slot as you explained.

    Wayne,
    I purchase and use JET chisels and bits (as does Chris Schwarz). For me, this slot is not seen so I don’t worry about aesthetics. Perhaps your chisels need to be touched up or sharpened.

    Woodworking Magazine has an article comparing different mortise chisels. The issue cover lines states "$9 Hollow Mortise Bit Just as Good as the $88 English Tool". You can download a digital copy (print issues are sold out) of the magazine at:
    http://www.shopwoodworking.com/product/293/38.

    Thanks,
    Glen

  3. glen

    Charles,
    Either of those floor models are great machines. Each is solid, well built and perform flawlessly. I never understood the reason for a tilting head in the Powermatic 719T. The tilt is not a benefit with chair building – the tilt is in the wrong direction. Also, at this time the Jet model is less expensive.

    As for through mortises, I don’t run into that as much as some woodworkers. You don’t find many through mortises on 18th- and early 19th-century furniture. It’s found mainly in Arts & Crafts designs. However, I would attack the mortise from both sides primarily to reduce the potential for blowout.

    BikerDad,
    I though about adding a photo of the sewing desk to the entry, but because it didn’t really relate to the subject, I left it out. Oh well! Here’s an old blog with my sewing desk shown: http://www.popularwoodworking.com/woodworking-blogs/editors-blog/evolution-of-a-woodworker-part-2

    If you would like additional information, please contact me.

    Glen

  4. Wayne Precht

    Glen,

    I recently picked up a used 719A and I have got to say it’s a heck of a lot better than the old drill press attachment style. However, I haven’t been impressed with the bits that came with it. I am not sure what brand they are, but they seem poorly machined and it’s hard to get them to run smooth. Is there someone that sells bits that fit this that are decent quality?

  5. Chuck Bender

    Glen,

    Your method is very similar to the one I use. Once I set my mortiser, I chop both ends of the mortise slot then I go right to "baby steps" you do. This helps keep the mortise nice and straight because the chisel is running partially in the previous hole. If that doesn’t make sense, I’ll send you some pictures. And, while I do a lot of things by hand, I truly derive no pleasure from cutting all my mortises with a chisel and mallet. This is definitely one of those tasks I believe is better left to the power tools. Thanks for the great post.

  6. Bikerdad

    Hey, can you direct us to the Shaker Sewing Desk? Sounds interesting, might make one for my daughter…

  7. Charles Brown

    Hey Glen, thanks for the insight on how you cut your mortises. I’ve been looking to upgrade from the plunge router (round mortises bother me) to a more substantial piece of shop equipment. How effective do you find the Powermatic/Jet for through mortises? Are you able to plough through the mortise in one shot or would you come at it with a pass from both sides?

Comments are closed.