Completing the Leg Mortises in the Workbench Top

In an earlier post, I started to chop the mortises in the under side of my workbench top.  I applied a few coats of danish oil and then got some help to flip the bench top right-side-up.

I used a square and marking knife to transfer the layout lines from the underside onto the edges, and then onto the top.  I used marking gauges (set to the same position from when I cut the tenons) to complete the layout.  I got out all the tools I would need, coffee foremost amongst them.

All the tools I need to complete the mortises.

I hogged out the majority of the waste with a brace and bit.

I bored most of the waste away with the brace and bit.

The rest will be cleaned up with chisels.

This would get a little “boring” if it weren’t for a good audio book.

The second mortise was the same as the first.

With the donkey work done, I cleaned up the mortises with the mallet and chisels.  I took my time to get these right, since they are going to be prominently visible on the finished bench.

The mortises cleaned up with a chisel and checked for square.

I’m happy with how these came out.

Over the next couple of days, I completed all eight mortises.  Some days, I only had time to do one pair after work.  In any case, a few days later, all were done.

Here is the benchtop with all 8 leg mortises chopped.

My design plan for the bench was to use wedged through tenons.  To allow room for the wedging, I need to flair out the mortises on the top side of the bench.

When I cut the tenons on the tops of the legs, I created a ¼” shoulder at each side of the tenon.  This means that the tenons are 5″ wide on the 5 ½” square legs.  In the photo below you can see my outer layout lines that represent the full size of the leg.  I planed to widen the top of the mortises to this width, while keeping the bottom of the mortise the same size as the tenon.

The outer layout lines represent the actual size of the leg.

I wanted the flaring of the mortise to taper evenly from ¼” on the top, to nothing on the bottom.  I figured that rasps and floats would be the best tools for this.

A shinto rasp and a large float used to widen or flair out the top of the mortise.

I had to take the handle off the rasp and use some heavy rubber-coated gardening gloves to get it to work best.

Using the rasp to widen the mortise on the top side of the benchtop.

I took the handle off the Japanese rasp and used it wearing a pair of gloves.

I kept going until I had a nice even taper that just touched the outer layout line.

You can see in the below photo that the shinto rasp did a decent job, but left the corners slightly rounded over.

I widened the mortise to the outer layout line.

The large float cleaned things up nicely.  You can see below just how much this widened the top of the mortise.  ¼-inch on each side doesn’t seem like it would be a big deal, but when compared to an unaltered mortise the difference is quite large.

1st mortise widened on both sides.

I cleaned up the cut and flattened the surface with a large float.

The huge float (that I bought at a garage sale) did a great job cleaning up the surface and flattening it.

The float cleaned things up nicely.

Both mortises flared out.

This was another slow and laborious task, but after another few days of after-work tinkering, I had flaired out all eight mortises.

All eight mortises ready for assembly.

Next up will be making a bunch of oak wedges, and cutting kerfs in the tenons in preparation for final assembly.

More soon.

– Jonathan White