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.

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.

No problem, brace and bit to the rescue.

A 1″ Irwin bit for use in a brace.

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 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.

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.

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.

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 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.

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 too snug… I’ll fine tune 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.

These are big mortises and it took a long time.

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