Cutting the Mortises in the Workbench Legs

With my mortises all laid out, it was time to start removing the waste.  I thought that I would start by drilling out as much of it as I could at the drill press.

A 1" forstner bit in the drill press.

A 1″ forstner bit in the drill press.

My drill press has a quill stroke of a little less than 4″, but this 1″ forstner bit will only allow for a hole around 2 ¾” deep.

With this bit, I can only go about 2 3/4" deep.

With this bit, I can only go about 2 3/4″ deep.

No problem, brace and bit to the rescue.

A 1" Irwin bit for use in a brace.

A 1″ Irwin bit for use in a brace.

After drilling with the forstner bit.

After drilling with the forstner bit.

I wanted to cut the mortises about 4″ deep, so I made a mark with a sharpie on the edge of the auger bit at the correct place.   I also found that putting a little wax on the edge of the auger threads every now and then, made the work a bit easier.

I marked the edge of the bit with a sharpie to indicate when I reached 4" depth.

I marked the edge of the bit with a sharpie to indicate when I reached 4″ depth.

I drilled the outer two holes first on the drill press, then took them to depth with the brace and bit.  I then went back to the drill press and drilled the two center overlapping holes.

The middle two holes drilled on the press.

The middle two holes drilled on the press.

Finally, I took the middle two holes to depth with the brace and bit.  I know this seems a little complicated or possibly a needless extra step, but I wanted to make sure that the brace and bit followed the well established holes created at the drill press which I knew were square to the leg.  I thought the brace and bit might be able to wander more easily if I drilled all four overlapping holes at once.

All four holes taken to 4" depth.

All four holes taken to 4″ depth.

4" deep.

4″ deep.

Then I had to repeat the whole process again for the other four holes in each mortise. Let me see, this is going to be eight holes per mortise and eight mortises… 64  4-inch deep holes.  I can certainly see why the hollow chisel mortising machine was invented.

Repeat the process for the other four holes.

Repeat the process for the other four holes.

Most of the waste is out, time for the chisel!

Most of the waste is out, time for the chisel!

I roughly chopped out the middle section of waste with a chisel and mallet and pared back some of the waste around the edges.  I used a block of oak with a good 90° edge to guide the chisel for the final cuts right on the knife-line.

I clamped an oak block directly on the knife line to guide the chisel.

I clamped an oak block directly on the knife line to guide the chisel.

I did the same to pare the side walls.

I did the same to pare the side walls.

It is surprisingly easy to create a mortise that tapers.  I found that the top and bottom of the mortise (the wall chopped into the end grain) have a tendency to get wider as you chop them deeper.  The sidewalls of the mortise (those pared from the side grain) seem to have a tendency to get narrower as you go deeper.  I made sure that I checked the mortise often with a combination square as I progressed.

I continually checked to make sure that the walls of the mortise were square to the face of the leg.

I continually checked to make sure that the walls of the mortise were square to the face of the leg.

Once I thought I was done, I did a test fit and found it to be a little snug.  I pared a little more away from the mortise walls and the joint slid home beautifully.

Just a hair to snug... I'll fine tune it.

Just a hair too snug… I’ll fine tune it.

That's got it!

That’s got it!

Once I had one mortise cut in each of the legs, I repeated the process to cut the second. This went quicker than the first four mortises.  Mainly because I had had some practice and was working more efficiently, but also due to the fact that the mortises intersect and some of the material had already been removed.

I connected the mortises from both sides.

I connected the mortises from both sides.

These are big mortises and it took a long time.

These are big mortises and it took a long time.

All eight mortises done.

All eight mortises done.

Laying out the mortises, cutting them, and refining the fit took me quite a lot of time.  I get to work in my shop for an hour here and an hour there, and I seem to be constantly distracted by other things (the kids mainly), but I bet this took me the better part of a week or more to get done.

In the next post, I will miter the ends of the tenons and drill the draw bore holes.

More tomorrow.

 

– Jonathan White

About Jonathan

I am a woodworker and hand tool restorer / collector. I buy too many tools and don't build enough - I need help!
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6 Responses to Cutting the Mortises in the Workbench Legs

  1. Very well thought out boring technique. Regards, Larry

  2. Pingback: Fitting the Draw-bored Mortise and Tenons | The Bench Blog

  3. joemcglynn says:

    Those are spectacular looking mortises, the use of a guide block for mating the walls is a great idea. I’m stealing this for the next time I need to do big mortises like this.

    The wood looks like Fir — did you have any issues with it dulling your chisels? I’ve had this with two brands of chisels when chopping into Doug Fir. It was really bad with my old Sandvik chisels, but even my LN chisels seem to suffer. They get dull, and also fairly quickly develop small nicks in the cutting edge.

    • Jonathan says:

      Hi Joe,

      The wood I am using is indeed Douglas Fir. I had it milled to order locally and it has air “dried” for almost two years. It is generally very humid here in Western Washington, so I use the term “dried” loosely.

      Now that you mention the chisel dulling issue, I have noticed that I seem to be sharpening much more often that I would have thought needed with a “softwood”. The darker rings of late wood growth in Douglas Fir really are quite hard. I wonder if Douglas Fir has a high silica content? I also was surprised at how fast my block plane dulled when I smoothed the end grain of the legs. After four legs the edge was trashed. I couldn’t believe how rounded over the cutting edge was when I removed the iron to resharpen it.

      I am also noticing the small nicks in the cutting edge of chisels. The frequent sharpening is especially noticeable when I’m using my western style bench chisels, my Japanese chisels seem to be less affected and hold their edge a little better. The only chisel that I haven’t had to resharpen is my English pig sticker. I wonder if the edge retention there might be due to the higher bevel angle? I suppose I could sharpen a bench chisel at 35 degrees and see what happens.

      Thanks for your input.

      All the best,

      Jonathan

      • joemcglynn says:

        Jonathan – that matches my experience with Doug Fir spot-on. I agree that it seems to be the darker drouth rings that are the culprit.

        I’m anticipating that I’m going to want to build a Marquetry Chevalet after the Boulle course I’m going to next week…and thinking about making it from fir. On the plus side, it’s plenty strong and readily available (I saw enough 6×9 timbers on craigslist last week to build a roubo bench for $75), but I’m not sure I want to dull that many tools.

  4. Pingback: Designing, Laying out, and Cutting Double Tenons to Attach the Workbench Top - Part 1 | The Bench Blog

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