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.
I hogged out the majority of the waste with a brace and bit.
This would get a little “boring” if it weren’t for a good audio book.
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.
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.
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.
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.
I had to take the handle off the rasp and use some heavy rubber-coated gardening gloves to get it to work best.
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.
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.
The huge float (that I bought at a garage sale) did a great job cleaning up the surface and flattening it.
This was another slow and laborious task, but after another few days of after-work tinkering, I had flaired out all eight mortises.
Next up will be making a bunch of oak wedges, and cutting kerfs in the tenons in preparation for final assembly.
– Jonathan White