# Thread: Round Mortise with Square Tenon?

1. Member
Join Date
Aug 2015
Posts
23

## Round Mortise with Square Tenon?

I see folks cutting mortise holes with routers. This leaves a nice rectangle with round edges. Then they cut rectangular tenons with square shoulders to go in the mortise. I don't really understand this. Is this a strong join? Perhaps I just watch too many youtube videos?

Many Thanks!

2. Router mortises are unfailingly perfectly perpendicular and perfectly sized. Tenons with square corners are easier to mill. The conundrum is to square the corners of the mortise or round the corners of the tenon. For me, it is tons easier (and faster) to pare the square corners round than to mess up the geometry of the mortises. A sharp chisel and learning some simple body mechanics in using it and bob's yer uncle.

3. My choice has been to go the route of loose tenon joinery. There are several advantages to this process. Basically, you make the mortises with a router and get rounded ends. After making tenon stock to proper thickness, round over the edges to match the mortise.

4. Also a good approach. Certainly easy peasy.

5. Originally Posted by Carol Reed
Also a good approach. Certainly easy peasy.

Especially for us lazy types!

6. Member
Join Date
Aug 2015
Posts
23
Okay, I read up on loose tenon joinery and it seems like a good place for me to start. Got a couple of questions.

To "round over the tenon" am I passing the cut to size tenon stock over a round over bit on four sides?

Uh Oh math may be required here, If I have 1/2" thick tenon stock to go into a 1/2" mortise I would use a 1/4" radius round over bit?

Thank you all for your patience!

7. Yep, your math is right. For a 1/2" tenon, you need a 1/4" round over on each edge.

8. Originally Posted by Bob Beasley
...If I have 1/2" thick tenon stock to go into a 1/2" mortise I would use a 1/4" radius round over bit?...
Yessir, I believe that's correct. I'm sure others will correct me if I'm wrong.

9. Member
Join Date
Aug 2015
Posts
23
Is there a recommended ratio of thickness of wood to thickness of mortise? For example if I had a 1" thick piece of wood would I cut a 1/2" mortise, leaving 1/4" top and bottom of the mortise?

Same question for length of mortise relative to width of joining wood? Seems like this would be very important when doing loose Tenoning.

10. I find dowel joints satisfactory. I decided that mortise and tenon joints were too complicated for a computer technician to take on.

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