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Mortice Marking Gauge



The other day I received an email inviting me to purchase the latest one-time tool from Woodpeckers, a mortice and tenon centre gauge ..

My first thought was that this was brilliant - what a great, quick way to mark a mortice (or tenon) in the centre of a stretcher. Then I looked at the price ($150), and that one had to pre-order now for 5 months time. I put away the credit card.

I still think that it is a terrific idea, and I must admit that the concept haunted me for some days. Today - Sunday - I decided to build my own version. So I looked around the workshop for something to cannibalise.

I found an old dovetail marker that had never worked and had been tossed into a drawer ...

This is the centre gauge I built ...

It slips over the stretcher this way ...

Marking out for a 3/4" wide stretcher calls for a 1/4" wide mortice. This one will be 2" long.

Step #1 is to mark off the 2" length (with room to avoid blowing out the end) ...

Now place the centre gauge between the two end lines (anywhere, it is not critical). Set the 1/4" mortice chisel against the centre, eyeballing it square ...

Press done hard so that you leave a clear imprint of the chisel ...

Now you have a choice - either use two single blade cutting gauges to mark each line individually (you will need to set these aside for the tenon) ...

... or use a mortice gauge, aligning the blades with the outer edge of the imprint ...

It has never been critical to centre the mortice, but this method does speed up the process (even though this is all a bit tongue-in-the-cheek). Is it accurately centred? I did three or four. None were perfectly centred. Some error creeps in. It does not matter. As long as you use the same gauge(s) and score from the reference side, each mortice/tenon will be marked at the same distance from the sides.

Regards from Perth

Derek

November 2013