learning how to make mortis and tenon joints

Are there guidlines on what size of mortis and tennon joint to make for a particular wood thickness?
I just had a project go really bad.
Wanting to learn how to make mortis and tenon joints I decided to make a simple chair. I have made some test joints that seemed to fit and work well.
First I purchased some 1x2 pine at home depot thinking it was not too expensive and if it did not work I would not be burning too much wood (using pine of such small dimension was probably my first mistake).
All the joints fitted nicely but while trying to assemble the last couple pieces I was having trouble getting the last couple tenons together after applying glue and using a hammer to force the issue when first one piece of wood split and then another and the chair is no more. Being new to this, are there guidlines on what size of mortis and tennon joint to make for a particular wood thickness?
One suspicion that I have is that 1 inch pine with a mortis cut into it is too weak. Once christmas is over I'm going to try some 1x2 maple and see how it works. Or should I try for something thicker for starters
We are planning on having a fire in the fireplace on christmas and I have lots of fresh kindling to start it.
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william kossack wrote:

<snip>
Some info here. http://www.wood-workers.com/users/charlieb/M&TPrimer0.html
-- Mark
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Biggest mistake we make is trying to make the joint too tight. In reality, the joint bears on end grain surfaces at shoulders and the gravity side of the mortise. The cheeks need not be tight, because they're really not the bearing portion of the joint.
If you can't dry fir the joint with ease, you should get out your plane and chisel and trim the cheeks. If you insist on putting a lot of glue in, make sure you don't bottom the tenon, and run a relief channel for air to fart out as you assemble. On pine, enough to run a screwdriver and press, some run a veiner or macaroni gouge groove in hardwood.
One third to one half the thickness is standard tenon. Wider the tenoned piece (more end grain bearing), the thinner the tenon may be.

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william kossack wrote:

Rule of thumb is 1/3 thickness for each section. It's not written in stone though (just wood). Making sure that it dry fits first would save a lot of pain. My 2 cents, Dave in Fairfax
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snipped-for-privacy@fairfax.com wrote:

I'll go one better. If you don't make sure it dry fits first, you're an idjit.
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Michael McIntyre ---- Silvan < snipped-for-privacy@users.sourceforge.net>
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On Sun, 21 Dec 2003 20:34:54 GMT, william kossack

RULE: Tenon is 1/3 to 1/2 the thickness of the wood it enters.
1 of 837 from Amazon.com:
Making Mortise and Tenon Joints by Taunton Press
From our local library:
search for "joinery"
Woodworking techniques : joints and their applications Author: DeCristoforo, R. J.
Notches of all kinds : a book of timber joinery Author: Mackie, B. Allan.
Woodwork joints Author: Hayward, Charles Harold
Practical & decorative woodworking joints Author: Bairstow, John E. N.
Joining wood : techniques for better woodworking Author: Engler, Nick.
The encyclopedia of jointmaking Author: Noll, Terrie.
search for "chairs"
Make a chair from a tree : an introduction to working green wood Author: Alexander, John D.
The chairmaker's workshop : handcrafting Windsor and post-and-rung chairs Author: Langsner, Drew.
Making classic chairs : a craftsman's Chippendale reference Book Author: Clarkson, Ron.
The weekend woodworker : 40 easy-to-build projects : shelves and cabinets, toys, tables and chairs, boxes and mirrors Publisher: Rodale Press
Fat girls and lawn chairs Author: Peck, Cheryl. (No idea what you'll find there)
Make a Windsor chair with Michael Dunbar Author: Dunbar, Michael.
Fine woodworking on chairs and beds : 33 articles Publisher: Taunton Press
========================================================= I drank WHAT? + http://www.diversify.com --Socrates + Web Application Programming
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....and then use the closest sized chisel you have :)
Rob
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Then mine should have been strong enough except for the pine I was using.
I'll have to redesign slightly for the next attempt and make the piece that broke first a bit beefier.
Larry Jaques wrote:

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says...

Are you sure your alignment was correct? Trying to force-fit a mis- aligned part could lead the the problem you described.
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I had done a test fit of the entire chair before I begain gluing. Everything fit and not so snug that I had to pound it together.
I'm now thinking the most likely cause is too much glue in the holes. Some bleed holes out the other end might be the solution. I have the home depot maple and as soon as weather permits I'm going to make another stab at it. However, I'm debaiting picking up some wider maple at paxtons for the back legs and the back cross piece that failed on the pine.
One problem early on is that I realized too late that I was gluing the chair pieces in the wrong order making it difficult to make the final assembly.
Mark & Juanita wrote:

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I do WW for a living (hey, call that a living....) but I periodically make-up one-off mortised and tenoned doors. The normal practice with these is to leave a "horn" on the end of the stile pieces (generally some 2 to 3in long) which you have mortised. The door is thus delivered to site with the horns intact and these are sawn off by the installation carpenter before he hangs the door in the frame. Ths is traditional English practice and is done for two reasons - first pine can be pretty variable stuff and it is easy to "pop" out the thin piece of wood at the end of a stile, especially if you are foxing (i.e. wedging) the joint - secondly the horns protect the top and bottom of the door during transit. There is less of a need to do this with hardwoods, but I still habitually leave about a 3/4 to 1in horn on these, too. Even so, fit is important - your tenons should slide into the mortises with a little bit of resistance - remember, you'll need somewhere for the glue to go and if your M&T is very tight and you are using a water based glue (PVA, aliphatic resin, etc) a very tight joint can "burst" through fibre expansion, especially if you haven't got horns at the end.
Hope this helps
Scrit

using.
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Hi William,
A couple of things. The first is, as a general rule-of-thumb is to divide your thickness into 1/3rds for the strongest joint. However, it makes things much simpler, whatever method you are using, to make your mortice the same width as your tool, be it hand chisel, morticing machine, or router bit. So select your tool to be as near to 1/3 the width as you can for maximum strength and maximum convenience.
The second is that pine is pretty variable. If you get old-growth stuff which was slow-grown in a high latitude, the rings will be tightly-packed and the timber quite dense, and it'll make a strong constructional timber. If you buy cheap stuff from a builders yard, which is more appropriate for making a stud wall, then you may find that it's fast-grown and harvested young, so the growth rings are widely spaced, and it's not really fit for something to take the huge stresses that a chair will have to take. If you've got a slim chair with a 200lb man rocking back in it, the joints are under huge pressure. 1" stuff might be ok in top-quality clears, but if you're using 5ths or 6ths stuff, then you might want to go up to 1 3/8" or so.
The third thing to consider is that if the mortice is at the end of the component, then there's not too much wood between the end of the mortice and the end of the component, perhaps as little as 1/4". so when you come to drive home a fairly tight-fitting tenon (as I personally believe they should be) then it's going to split out. The solution here is to mark up the component with the mortice to size, but *don't* cut it to size - if possible - until after glue-up: leave a few inches of overhang on the end nearest the mortice (we call these overhangs "horns"). This will greatly reinforce the joint when you're malleting the tenon home.
HTH
Frank

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http://www.taunton.com/finewoodworking/pages/w00011.asp
william kossack wrote:

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