Mortise & Tenon Questions

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Forum topic by KnickKnack posted 10-14-2009 07:57 PM 2510 views 0 times favorited 12 replies Add to Favorites Watch
View KnickKnack's profile


1062 posts in 2983 days

10-14-2009 07:57 PM

Topic tags/keywords: mortise tenon question

So, I’m finally biting a bullet and trying some “proper” joints, specifically mortise and tenon.

Q1: I can’t really find much information on how tight should it be?
  • 1) Should drop in under its own weight
  • 2) Should require a gentle push from me
  • 3) Should require a gentle tap with a mallet
  • 4) Should require a thump from the mallet
  • 5) Should require clamps to squeeze it together
    (I’m thinking positive here, like I can actually so anything with the required degree of accuracy)

Q2: I don’t have a lot of tools available (as in available for purchase), so I’m making the mortise with the hand-held router. This leaves me, obviously, with rounded ends. Chisels and me don’t really seem to get on, even though I keep trying, so the question is whether it’s OK (obviously it isn’t what a master craftsman would do) to simply cut the tenon a little smaller and leave the hole with the rounded ends since this shouldn’t reduce the glueing surface very much, and it’s hidden anyway.

-- "Do not speak – unless it improves on silence." --- "Following the rules and protecting the regulations is binding oneself without rope."

12 replies so far

View a1Jim's profile


115166 posts in 2994 days

#1 posted 10-14-2009 08:03 PM

They should fit sung but not tight for a fit you can pull out but not fall out when you hold the tenon part of the joint. If your using a router you might consider loose tenon joinery it makes for a strong joint but easier to make with a router. If you search they have a few articles about loose tenon joinery.

-- Custom furniture

View lew's profile


11261 posts in 3172 days

#2 posted 10-14-2009 08:05 PM

The tenon should fit so that you need to use a gentle push to seat it. Any tighter and it may not fit after the glue is applied and any bigger wont provide the surface contact necessary for proper gluing.

It is permissible to make tenons slightly smaller, in length, than the mortise to allow for positioning. Have you considered a wood rasp or course sand paper, on a wooden block, to round over the tenon corners?

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View KnickKnack's profile


1062 posts in 2983 days

#3 posted 10-14-2009 08:17 PM

Thanks for the answers so far.
I’d never even heard of “loose tenon” before, and I’ve read a lot of stuff. Having surfed it seems like a “mega-biscuit” sort of joint. I think I might be able to manage that, although how exactly I’ll manage to rig everything up to route into the end of a 2 metre long piece of wood I’ll have to think about – one day maybe Portugal will discover router tables.
As for rounding the mortises to fit the holes – I’ve tried that but it always ends up smaller than the hole anyway, and getting it right down to flush with the rest of the piece is a challenge.

-- "Do not speak – unless it improves on silence." --- "Following the rules and protecting the regulations is binding oneself without rope."

View Craftsman on the lake's profile

Craftsman on the lake

2504 posts in 2855 days

#4 posted 10-14-2009 08:37 PM

A few months ago I made (with the assistance of a few people here at LJ’s) my first raised panel cabinet. I had made a few mortise and tenon joints and discovered loose tenon. I had a new Bosch router. Making these with a router with a jig is a snap. I’ve done some regular tenons but I’ll tell you I’m sold on the ease and strength of loose tenons. And they are sort of ‘adjustable’ so you can make them fit well.
Here is a link to a slideshow from my project blog that will show the way I made the loose tenons and the jig for them. The rest of the slideshow is the rest of the cabinet. Maybe it will assist you. It will download and you’ll need to open. It will play in quicktime.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View a1Jim's profile


115166 posts in 2994 days

#5 posted 10-14-2009 08:42 PM

There are a number of shop made jigs that can be made for loose tenons take a look on youtube.
Here’s one but check a few of them out there to get the feel for the different types jigs that can be made.

-- Custom furniture

View Thuan's profile


203 posts in 3235 days

#6 posted 10-14-2009 09:20 PM

Here’s a link that pretty much explain everything from an engineer’s point of view.
Be sure to watch the other stuff this guy makes. It’s pretty much genius.

-- Thuan

View PerveyorofSawdust's profile


16 posts in 2559 days

#7 posted 10-28-2009 03:20 AM

Thanks knick knack , i just joined recentley and you have asked everything i wanted ask about m and t joints, and you got some real good answers, thanks guys …......Gotta love lumberjocks!

-- Gordon,Sydney ,Australia..Metal for money..Sawdust for love!

View lumberrookie's profile


18 posts in 2578 days

#8 posted 11-05-2009 02:17 AM

If you cut a lot of M&Ts May I humbly suggest investing into a Mortise machine. a bit costly at first ($150-200) but saves lots of time and is very accurate. I find it hard to do without.

-- Steve

View dryhter's profile


74 posts in 3021 days

#9 posted 11-05-2009 03:05 AM

Hey KnickKnack, #2, then three, then 1 or four, never five.
When checking the joints make sure that you are at 90 or at least able to attain 90, if that is your desired angle.
You did not say what the joints were in, a door, a face frame, a workbench,or something else, it makes a little difference, not much, but a little.
Remember that glue is stronger than wood so use copious amounts of glue, unless of course you want to be able to take the joint apart. And lastly always use a mechanical fastener, pegs, dowels, nails or pins.
I have some podcasts that I made while building a woodworkers bench that deal with mortise and tenon joinery, if you would like a link let me know.
I prefer to cut my mortises with a round shoulder, less chance for failure, just route or pare with a chisel the radious on the tenon
Dave @ ”":

-- Chips and Shavings/ see you at

View matt garcia's profile

matt garcia

1877 posts in 3089 days

#10 posted 11-05-2009 03:25 AM

The tenon should fit in the mortise with a slip fit.

-- Matt Garcia Wannabe Period Furniture Maker, Houston TX

View skidiot's profile


58 posts in 3062 days

#11 posted 11-05-2009 03:36 AM

I have done a few M+T joints, some better than others. I always use expanding polyurethane glue. That way even the loose ones will be nice and strong when finished.

-- skidiot northern illinois

View a1Jim's profile


115166 posts in 2994 days

#12 posted 11-05-2009 06:27 AM

M&T are great joints even though everyone thinks they are the strongest joints around there are stronger joints out there as proven in test though FWW and Home but most the time the do the job very well. something you have to keep in mind is to size them properly for the size wood and what there use in. There are tons of jigs out there any were from shop made to My Muti router and beyond what I recommend is to make a shop made jig if your up for that kind of thing and then if you don’t like it buy a factory made jigs . One doesn’t even use a router it uses a drill special bit and the jig. I’m talking about loose tenon M & t . In another test they found good old yellow glue was as strong or stronger then all glues including epoxy and polyurethane for M & T joinery. They also found that yellow glue was stronger in joints that were tight and joints that were loose than other glues.

-- Custom furniture

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