Mortises - How Not to Do Them

I had no idea how much trouble I was going to have making the mortises and tenons for the base.  I tried a variety of methods and they were all less than satisfactory.  I am embarrassed by my poor craftsmanship on this part of the project.  My defense is that the problems I encountered, while probably inevitable, nonetheless took me completely by surprise.  Bottom line is: I really needed a drill press to make this workbench.

2009.07.04

First Bad Idea: Forstner Bit in Corded Drill

I started by putting a forstner bit in a corded drill, and making a couple holes where one of the mortises would go.  Of course, a forstner bit doesn’t like to dig down where you start it, it wants to walk all over the surface, chewing everything up as it goes.  Once I finally got it started into the wood, it did mostly stay in place, but steering by hand, inevitably the path wandered to one side or another.

Forstner bit in corded drill to start leg mortise
Two holes drilled in leg mortise

Second Bad Idea: Chopping with Normal-size Mortise Chisel

After making a couple holes, I began chopping out the waste between with a mortise chisel.  I also endeavored to make the straight side walls of the mortise.  Now, obviously this is the right sort of tool to use for a mortise… except the largest mortise chisel I have is 3/8″, and is meant to chop a 3/8″ wide mortise.  Trying to drive this relatively small chisel in such a large mortise was my second mistake.  I followed up with some of my bench chisels, but it didn’t improve things much.  Flat and square sides?  No chance.

Chopping the waste with a mortise chisel
Chopping leg mortise with chisel

Third Bad Idea: Rasp

Not happy with the wavy, irregular results of my drilling and chopping, I then decided to use a fine cabinet rasp to try to even things out.  The side walls did become more planar, at least, but they were also chewed up.  The fit was so sloppy that I could just drop the tenons in, no pressure needed.

Using a rasp on leg mortise
Test-fitting mortises and tenons in a leg

2009.07.17

Fourth Bad Idea: Start With Chisels

In the next leg, I decided to start each mortise with chisels, thinking that I would have more control.  It started out well, but as I chopped down layer by layer, I could not seem to keep the side walls flush and square, yet again.  After I got down an inch or so, I used a forstner bit in the drill to help clear out the middle to save some time and effort.

Defining mortise edges with bench chisels
Chopping leg mortise with chisel
Leg mortise in progress
Bad leg mortise

Take a Break

2009.07.18

I was so put out by what had happened that I stopped working on the workbench for a couple months.