Morticing by Chisel II
It is four years since the last tutorial on morticing and time for an update. We all continue to evolve our techniques - becoming more efficient, making it easier. Some aspects have changed, and I have documented them below.
These are the tools I used. ¼” oval bolstered mortice chisel, mallet, mortice gauge, marking knife, and small square.
Marking out the mortice
The wood here is Tasmanian Oak, which is a just a little harder than White Oak.
Pencil in the outer lines (in this case, 2” apart), and then use the chisel to mark the width of the mortice.
Insert the ends of the blades at the outer edges of the chisel mark, and then slide the body against the reference side of the stretcher. (Set aside the gauge to later mark the tenons).
Knife the lines at the ends.
Drill a hole at one end equal to the final mortice depth. This will be 1” in this case. The hole is to provide space for waste chips.
Once drilled, I pare away about 1/16”. This is to make it easier to chisel within the lines. This is optional. You may prefer to simply chop inside the marked lines.
The stretcher is clamped over a leg. The end of the clamp offers a reference for vertical.
The chisel is placed bevel towards and about 1/8” from the hole, then driven straight down.
It should manage to reach about half the final depth at this point.
The only chopping direction is straight down. No attempt is made to lever out waste. The waste is being forced into the (drilled) hole.
Here is the distance the chisel is moved each time.
As the chisel moves further from the hole, there is a progressive increase in the depth it achieves.
About half way you will need to lever the chisel to unstick it. This will also push the wste towards the hole.
By the three-quarter point it is likely that you will be at full depth.
Continue to the end of the mortice …
… and then turn the chisel around and return.
About half way you can lever out the chips (I should have reversed the blade here!).
Continue to the end of the mortice and clean up.
A tad bit of tidying up left to do at the one end, but this is a functional mortice.
The best way to test the mortice is to fit the matching tenon. The length of the tenon cheek is a smidgeon under the 1” depth of the mortice.
A good fit with minimal tuning, demonstrating the mortice is square.
Regards from Perth
Derek
September 2013