Through Mortise

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Forum topic by pete79 posted 03-21-2011 03:38 PM 1195 views 0 times favorited 6 replies Add to Favorites Watch
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154 posts in 3342 days

03-21-2011 03:38 PM

I’m about to embark on attaching a bench seat to the legs of a bench that I’m making for my parents and have a question about this step…

I’m thinking that a through mortise, leaving the tennon on the top of the legs slightly proud of the surface of the bench seat might be a nice touch. My tool choices for cutting the mortise are a plunge router, or hand chisels. I’m going through a 8/4 slab of red oak, and the tennons will be about 1” x 1”. I’ve never cut a mortise by hand before, but am thinking this is my best option?

My main issue is that I’m nervous about going all the way through my really nice 8/4 slab of oak, so I probably just need to get over that. But i’m looking for any words of wisdom, tips, tricks, etc. before I go for it.


-- Life is a one lap race.

6 replies so far

View chrisstef's profile


17761 posts in 3207 days

#1 posted 03-21-2011 03:52 PM

To give yourself a nice clean hole drill half way through then flip it over and rill the other half. It will prevent any blow out.

-- Its not a crack, its a casting imperfection.

View Lee Barker's profile

Lee Barker

2170 posts in 3051 days

#2 posted 03-21-2011 04:25 PM

Agreed, chrisstef. Then cut from the top to square it up, but first chamfer the bottom edges slightly with your chisel so you don’t push out a splinter that would show on the end grain side.



-- " his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View richgreer's profile


4541 posts in 3276 days

#3 posted 03-21-2011 05:01 PM

I think I would start with a 1” drill bit and use a backer board to prevent tear out. A router and jig with a small (1/4”) straight bit can partially square the corners from each side. You can finish the job with a chisel.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

View David Kirtley's profile

David Kirtley

1286 posts in 3199 days

#4 posted 03-21-2011 05:31 PM

You can also use a coping saw to remove the bulk of the waste after you drill out. Then it is just cleanup with the chisel.

-- Woodworking shouldn't cost a fortune:

View Loren's profile


10477 posts in 3849 days

#5 posted 03-21-2011 06:03 PM

Like David says. Drill and cope the hole. Then trim to square
with a chisel. Pretty easy to do it this way.

View stefang's profile


16133 posts in 3535 days

#6 posted 03-21-2011 06:55 PM

You might also drill through with a very small bit at the 4 corners with a backing board clamped to the outside to prevent any breakout. This will give you a perfect guide for the outline of your mortise so you can finish the chopping from the outside without breakout. For this technique to work, your holes have to be at an accurate 90 degree angle.

-- Mike, an American living in Norway.

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