Mortise Hell

So I’m cruising along on my little Byrdcliffe-inspired cabinet and I run headlong into the door, specifically the mortise and tenon joints on the door frame.  The carcase of the cabinet is all glued up, nice and square with nice night joints.

Cabinet carcase glued up

Cabinet carcase glued up

But the mortises for the door frame are giving me fits.  I’ve made  a handful of mortise and tenon joints – a small enough number that I can probably count them on my fingers – over the past two years.  Generally I’ve used a router or drill to clear the waste and squared things up with a chisel.  On a few I’ve chopped them directly, which felt pretty good.  There is a joint on the Blacker House sconces that makes a L-bracket to hold the sconce body, I chopped a pair of mortises for that joint that came out pretty nice.

Dual through mortise and tenon on the Blacker sconces

Dual through mortise and tenon on the Blacker sconces

I know from experience that if the mortises on this door are just right the door won’t be right either.  The mortises need to fit the tenons nice and snugly so there is a reliable glue surface, and they need to be exactly true or the door don’t lay flat on the bench.  Ask me how I know that, go ahead…

So yesterday I ended up chopping bunches of mortises for practice.  It wasn’t much fun, kind of frustrating because I don’t seem to be progressing past a point.

My initial problem was glowing out the end, but I can avoid that by making the stiles over-long and then trimming them to length after the door is assembled.

End blowout, this is from the chisel digging in

End blowout, this is from the chisel bevel digging in

More end blowout, this is the more typical problem just from the pressure splitting out the wood

More end blowout, this is the more typical problem just from the pressure splitting out the wood

I tried pre-drilling the mortise, but on this particular mortise that just gave me a sloppy, wallowed-out slot.  The drill bit wanders a little, and truthfully it didn’t really seem any faster to me.

So I practiced chopping mortises with both a regular 1/4″ chisel and an English-style mortise chisel.  I think there is something wrong with the geometry of the mortise chisel as it tends to stick in the mortise.  I’ll have to check it with some calipers, but I think it’s wider behind the cutting edge.  It’s a lot harder to keep it aligned too, the shaft isn’t as true and my LN chisel.  I suspect that is a factor in my difficulty in getting the mortises truly plumb.

Here is what I’ve found so far.  Having the workpiece (and mortise) oriented so it is straight in front of me make it loads easier to keep the chisel plumb and have the mortise end up mostly straight.  But none of my mortises so far have been straight enough.  I have a piece of scrap that I test fit in each, and it’s never quite right.  Generally it leans away from the rabbeted shoulder slightly, which isn’t going to work.  I can pare the mortise to get it to stand straight, but then it’s too loose.

The other thing I’ve found is that it’s relatively easy to get a 3/4″ deep mortise, but getting to a full inch across the whole mortise take a lot more work.  I don’t know if that’s technique or what.  I’ve been using the “Central V” approach, I’ll have to experiment with other approaches.  In fact, as I write this I’m remembering a blog post by Chris Schwartz that talked about his struggles with mortising, and I’m already feeling better.  In his article, he mentions another site that has a number of great articles on hand mortising, I’m going to read all of those articles today, and do some more practicing tonight.

Practice hasn't yet made perfect, it's only made scraps and frustration

Practice hasn’t yet made perfect, it’s only made scraps and frustration




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10 thoughts on “Mortise Hell

  1. theindigowoodworker

    Try leaving the ends long then cutting to length after the mortises are all chopped. You don’t have enough stock on those end mortises to support the pressure of chopping the mortises.

    • Thanks, I realized that after I cut the stiles to length. The real problem for me is getting the mortises plumb.

  2. I chop a lot of mortises by hand and in my experience the easiest way to maintain square is to hold the chisel with the bevel facing away from the initial “v” you’ve opened up. That way you can hold the chisel square and plumb to the work and the chisel will ride down its bevel. The other thing is “tappiedy, tap, tap” that chisel. Trying to wail on it will cause it to twist or follow the grain more. You shouldn’t be hammering hard at all. I try to make my initial v cut as deep as possible but you almost always have to traverse the mortise a couple times to get to depth. I just finished a kitchen table base with 10 4″ through mortises all chopped by hand!

    • Thanks for the feedback.

      Do you have any pictures of your table project? I looked on your blog and saw this sketch up model, looks like a fun project.

      Table Plan

      • I’ll have post up pretty soon. My kids are on spring break right now so I have no time!

  3. Paul Sellers has a jig that he made for chiseling mortises plumb. Two pieces of wood – one piece of a thickness equal to the inset to the mortise wall from the outside of the stile/rail, and the other piece which is longer and clamps to the side. It looks like a long cross grain rabbeted board.
    You clamp it to whatever you want to chop and it keeps you plumb. You can make it out scraps and as high as you think you need help keeping the chisel plumb.
    I’m not sure if he has a you tube video on this but his coffee table Master Woodworking class has it.

    • I remember seeing that — the rabbet on these parts serves kind of the same purpose, although a higher fence would probably help too. It won’t work with my old-school mortise chisel as it’s not an even width. I think I’m going to need to retire that tool (or grind it true, making it smaller).

  4. paul6000000

    I always clamp the rail I’m mortising against piece of scrap held in my end vise. The scrap is tall enough that I can use it to judge the angle of my chisel against. Using the end vise means I can be standing directly in line with the mortise and not leaning over the bench to sight the angle.

    I’ve had bad luck using regular bench chisels. The wedge shaped cross section seems to get stuck easier and there’s more chance of splitting the rail.

  5. Thanks Paul. I gravitated toward using my tail vise as you suggested, clamping a board in the vise and then clamping the workpiece to that. I picked up a couple of ideas from Jeff Gorman’s site ( that I want to put into practice (literally). He has some good ideas for how to orient the bevel. He also points out that if the chisel is slightly twisted (the cutting edge not perpendicular to the sidewall) it will drive the chisel at an angle. I realized the same is probably true if the cutting edge isn’t exactly square to the shank of the chisel — it’s a wedge and it will drive the chisel off plumb.

    My mortising chisel has a problem – I measured it and it has a swell behind the cutting edge, that is causing it to get stuck in the mortise.

    Lots of little problems, I think I’ll get closer next time I can get out to the shop to practice, than I’ll finish this door.

  6. Pingback: Byrdcliffe (ish) Door Done (ish) | McGlynn on Making

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