door mortice thickness

[wallace]

I am making a door which is 57mm thick, my biggest mortice chisel is 13mm. Is this big enough to have a single mortice/tennon or should I have a double mortice with a 10mm gap?

 

[Steve Maskery]

Well I guess it depends on what sort of forces are going to be placed upon it.

You could take two cuts to make the mortice 19mm or so, if you wanted just a single, trad, 1/3 tenon.

Personally I'd use a 3/8" chisel and make it a double tenon in fifths, but it's not an easy joint to get right. Not only does each tenon have to fit its mortice accurately, but they have to be exactly the right distance apart, otherwise each one will foul the entrance of the other. But when you get it right, it is a fantastically strong joint, as well as being beautiful.

You need very good hand skills, or the right jig for the job, and here I have to stop writing...

 

[Phil Pascoe]

A 13mm tenon would be strong enough in 40mm timber ... once it's glued up ... Why make work? It's only a door.

 

[wallace]

Thanks steve I don't think I'm ready for complicated, I think I'll go for the one big one

 

[Steve Maskery]

Wallace - It's not complicated, it's just precise. It's not the same thing...

Phil - the door is 57mm, not 40mm. I'd suggest that 13mm is OK but not optimum.

 

[Phil Pascoe]

I wasn't suggesting it was optimum - just adequate (and quickest and easiest?) My point was that if the door was 40mm you wouldn't say the tenon was weak - so why would you think it inadequate in a 57mm door? Life's too short.

 

[Steve Maskery]

Yes, fair enough, but as I say, it depends on what forces are going to be exerted on it.
But yes, 13mm is pretty much good enough for most normal applications.

The one downside of sub-third proportions is that if the joint shrinks back there can be a significant water ingress issue. If this is internal , then that is of no importance whatsoever.

 

[woodbrains]

Hello,

A 13 mm tenon in 57mm stock is too thin. Aside from the weak joint, there needs to be more thickness to the tenon, to hold the member it is in, flat. Also, the shoulders 22mm wide wil gap eventually. Even in a 40mm door I would go for an 18mm tenon. I'd definitely do twins in 57. Short life or not, re-doing is an even bigger waste of time.

Mike.

 

[PAC1]

I use double tenons 10mm wide positioned as you say with a 10mm gap that way both tenons are within the rebate. If you have or can make a tenoning jig for a table saw then the tenons are not difficult. The alternative is a 15mm or 18mm tenon.

 

[RobinBHM]

A 13mm tenon is certainly strong enough for a 57mm thick door. Its best if the top and bottom rails are through tenoned and wedged. If the mortice is wider on the outside and tapers, the wedge will expand the tenon and help lock in place. Wedges are fitted in saw cuts. A thicker single tenon doesnt increase the glue area and can weaken stiles.

Double tenons are possible and tooling is becoming common for large joinery manufacturers, but the precision needed makes them difficult to machine.

Mid rails may not be through morticed as there is a risk of stiles bowing.

Always include a haunch

It is good practice to chamfer or sand a small round at the joints before assembly so you get a V. If the joints are left square, the expansion and contraction of the rails will cause the paint to crack at this point eventually.

 

[wallace]

Thanks for the door making advice chaps. The door will not get wet in its position. It is made from laminated ash and will be half glazed and raised panels. Whats a good width for the bottom rail?

 

[blackrodd]

A nice chunky door like that I'd make out of 5" stiles and head, 9" bottom rail and 7" middle rail.
As Robin BHM said, through mortice the top and middle rails.
Please post a pic of the finished door, An ash door will look really good, A lovely timber.
Regards Rodders

 

[wallace]

Cheers Rodders, its amazing how much timber goes into a door. When I originally started this I thought those hefty lumps of ash will be plenty big enough for a door. By the time they were squared up they looked a bit puny so I cut them down the middle and added some more in the middle. It looks like I will have to upgrade my rails a bit, they are only 4.5" at the moment. The ash is really nice with some decent grain.
This is a door I made for under the stairs recently.