Using shims to draw bore mortice and tenon

**sdbrett** · 12th May 2021, 11:05 AM

All the guides I've seen about draw boring a mortice and tenon joint perform the process in several stages. Bore a hole though the mortice, insert the tenon and make a make, bore a hole through the tenon with a 1/16th offset from the shoulder.

Is there a reason that draw boring is done this way instead of placing a shim under the shoulder and only boring once?

I'm curious about this as I'm about to do a few double tenon joints and using a shim would make it a lot easier to ensure the rod is aligned the entire way though.

**auscab** · 12th May 2021, 12:18 PM

If I'm understanding the idea of your use of a shim use correctly. The mark on the tenon has to be back towards the shoulder 1/16th .
Placing a shim moves the tenon out so is going in the wrong direction for a mark or hole .

**sdbrett** · 12th May 2021, 01:38 PM

Oh yeah, completely brain farted on the offset direction

**auscab** · 12th May 2021, 03:01 PM

I just glue and clamp the mortise and tenon together, punch a mark then drill and add the peg . I think back in a workshop in the 17th to 18th century they would have done the same . It’s a lot faster and gets the same result . Draw and bore is for those without a clamp or two or a job to big for your clamps .

**sdbrett** · 12th May 2021, 03:27 PM

Originally Posted by auscab

I just glue and clamp the mortise and tenon together, punch a mark then drill and add the peg . I think back in a workshop in the 17th to 18th century they would have done the same . It’s a lot faster and gets the same result . Draw and bore is for those without a clamp or two or a job to big for your clamps .

Clamping is the reason which I am considering draw boring.

**Blackforester** · 13th May 2021, 11:21 AM

An easy way to mark the hole in the tenon is to use a smaller brad point drill bit and use it like a center punch against the wall of the hole in the mortice piece. No measuring required.

**GraemeCook** · 13th May 2021, 05:49 PM

Originally Posted by Blackforester

An easy way to mark the hole in the tenon is to use a smaller brad point drill bit and use it like a center punch against the wall of the hole in the mortice piece. No measuring required.

Spot on; so easy:

drill the dowell hole throgh the mortice,
insert the tennon,
use a brad point bit one size smaller than the dowell to mark the tennon,
remove the tennon and drill it with the dowell-size bit,
sharpen the dowell a little with a pencil sharpenner,
reinsert tennon and drive dowell home.
QED.

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