Handmortise

In a small response to years of subtle but predatory marketing on PBS that has
newcomers asking about mortising machines for their early projects, I prepared a short
primer this morning in the shop to answer a younger man's question. The entire session,
including stock preparation and photography, took 30 minutes. The actual mortise
chopping took 4 minutes, and I wrote this up on my lunch break.

First, you need mortise, not paring chisels. These Japanese ones below I bought from
Highland Hardware when they first opened more than 2 decades ago to replace the badly
worn family ones.

Note the flat bevels in the photo above; not hollow ground and no secondary bevel. These
are laminated blades designed for striking, and they come in the exact width of your
intended mortise, Ľ, 3/8, and ˝ inches.

Their bevels should be touched up on the hone every time you use them; your stones ready for use
should be a permanent fixture on a corner of your bench. Honing these is easy; just index the flat
bevel on the stone. You also need to hone the back dead flat, and I also hone the sides lightly on
the fine stone to remove any burrs. I use a set of 4 Arkansas stones all the way to the finest "black"
grade, but you can use what you normally sharpen with. I wiped the oil off the stone and chisel for
clarity; don't hone them dry or the stone's pores will clog.

Also note that the backs are hollow ground to facilitate easy flattening as you hone them
during their life. You can see the hollow above the edge

I do a final stropping on the stitched muslin wheel with Knifemaker's Green Rouge. Hard felt
wheels are the best for this, but they are expensive

Then I lay out the mortises on the prepared stock. First, the mortise gage double tines are set
to the width of this half-inch chisel. Then the mortise gage fence is set for mortise location on
the stock, and lines scratched. Want to have the mortises dead center? Simple, just run the
fence down the other face of the stock, compare the marks, and adjust the fence until the
marks are identical

It's a simple matter next to mark your mortise width with try square and marking knife. I'll cut
a simple blind double mortise and have used a pencil to make the lines clear in the
photograph. You need to leave your pencils in the drawer for this and other joinery marking,
as they are insufficiently precise

The next chopping sequence is from the center of the mortise, and the waste merely
levered out…splitting rather than cutting the wood along its long grain. My training aid
today is a 2 X 2 of sopping wet Douglas Fir from the scrap pile out in the weather…. hard,
tough and splintery. Your dry cabinet hardwoods will be easier. When working with highly
figured wood such as Birdseye Maple you are afraid to split, then simply strike the outline
of your mortise lightly with a paring chisel, first.

I repeat chopping from end and center, levering out the waste until I reach the desired
depth; then I reverse the chisel and use it bevel-down to clean up the mortise bottom.

The final result is a little furry because of the wet wood, but entirely satisfactory. There
is a small chip-out at the top of the right mortise, but this will be completely hidden by
the tenon shoulder when assembled.

Frankly, even working in large, commercial, 3-phase shops, I never found many
mortising machines that were entirely satisfactory. The bits are difficult to sharpen so
you need two sets of them for production work, and the over arm design likes to flex
under pressure, especially when the bit is getting dull, which also tends to pull your
work piece out of alignment with the fence.

Why bother? These simple, inexpensive tools
and a shop-made mallet are all you need to do
mortise and tenon joinery on one-off projects
for the whole of your lifetime