Replies

1. 
   user-148830 | Oct 07, 2008 06:30pm | #1

   Hi,
   You need to learn that you are the designer in the shop. The material you work with is wood, not metal, and it moves over time. Sometimes it moves after years of sitting quietly. I just watched a 20 year old door move on me in my house in a very very dry spell.

   The guidelines I will outline for you are the ones I think work. Others will disagree.

   I make my tenons as wide as my chisel or router bit. It all depends on what I'm cutting with. Make sure you have enough wood left behind after your mortise. It's no good taking away too much material because that's what a formula says. This means you have to consider if other mortises are also occurring in this area. I draw my joints out full scale and look at how much wood is left to hold a leg or stile together.

   Generally speaking my mortises are no thinner than 1/3 the full width of my mortise stock, but often a bit larger. Depth is dependent upon the ease of mortising. If I can go deep, then I'll get more gluing surface. But I never get closer than 1/4" to any wall, side or edge.

   Width of a tenon is determined by specie, how the wood was milled, and where it's going. I like to keep my tenons under 3" in width so that shrinkage is minimized. If I have a wider rail, then I split the tenon into two separate tenons, hoping, hoping, there is no good evidence one way or the other, hoping that my two tenons will move less individually than as one wide tenon. This will give me, refer to point one above, more wood left behind in my mortise.

   I know of no article that gives specific guidelines on this. You can look at my book on joinery, The Complete Illustrated Guide to Joinery, for more joints. As I say it will depend on what you're building.

   Oh, shoulders. Shoulders are structural as they help decrease racking. Make them as long as you can to increase triangulation across a joint. They also hide a joint so a bottom shoulder for me is about 1/16". A top shoulder is used only when needed, again it's small. Haunches on the other hand can be used in a variety of situations. Please look at my book. The section on mortise and tenons I would guess is about 100 or more pages long. One could argue that all joints are either edge joints or mortise and tenons. It's not easy to summarize their design. Good luck.

   Gary Rogowski
   Director
   The Northwest Woodworking Studio
   Portland, Oregon

1. 
   woodnwine | Oct 10, 2008 05:44am | #2

   Gary,

   Thank you for your reply and expertise.  Eventhough others might "disagree" I now have a reference point.  I am going to use your suggestions on my project and learn from them.

   Thanks for your help , your time, and your contribution to FWW.

   Alex

2. 
   user-231372 | Oct 22, 2008 03:39am | #3

   Gary,Question on the top shoulder of the tenon - you suggested "use only when needed". I use them on a regular basis, if only for hiding any mistakes. Gaps at the top no matter how small seem worse than any slight mismatch in the top shoulder. Any further insight on why 'only use when needed'??DanGo Bears!

1. 
   user-148830 | Oct 22, 2008 04:56am | #4

   Dan,
   If someone puts Go Bears on a message, they leap to the front of the list. It's as simple as that. When needed covers the exact situation you refer to: where an unsightly gap at the top of a mortise needs covering. They serve no other purpose unless you're cutting down on the width of a tenon for shrinkage purposes. Then shoulders top and bottom and maybe some haunches top and bottom will help to minimize the shrinkage in a tenon while still providing good strength against twist. One other situation for a top shoulder is when you don't run a haunch up top and need to bring your mortise down off the end of your leg/ stile. Please send me some defense. Gary Rogowski
   The Northwest Woodworking Studio
   A School for Woodworking
   Portland, Oregon

1. 
   user-231372 | Oct 23, 2008 04:04am | #5

   Gary,The Bears are beautiful (of course only when they are beautiful). I am originally a Chicago boy as both my parents are Northsiders. I think my dad had tickets when Bronko N. was playing _ I lie. I have a huge soft spot in my heart for them - '85/'86 was great. I won the office pool thru the season (always picking the Bears) and they covered the spread virtually all way. '06 Super B. or whenever it was, was hard to get excited about since they probably did not belong there...On the top shoulders - I plan for them from the get go. Unless you cut the tenon first, why not put them in just in case. I cut mortises first, so I can make tenons to fit but inevitably and in order to slightly 'rock' them into place at gluing, I get a gap. The gap ends up on the top due to gravity - not much of a gap. I suppose I could make sure at glue up to eliminate the top gap but why worry at all. Hence why I like top shoulders. With the double tenons suggested for tenons longer than 3 inches I suspect top shoulders would be even more convenient. How would you cover/minimize both of the gaps. I confess - even though I have your book I have never used a double tenons. One day I will.Dan

1. 
   user-148830 | Oct 24, 2008 12:40am | #6

   Dan,
   We used to listen to Jack Brickhouse broadcast the Bears games every Sunday. Willie Gallimore, J.C. Caroline. I got Rick Casares autograph. Dem good ol days. After Luckman it was all downhill until Jack Concannon and then McMahon.Okay woodworking. I use small 1/16" shoulders top and bottom of my tenons, twin or single engine. It don't matter. These aren't huge, are easy to cut by walking a chisel over from one shoulder to the other, and easily cover any wear on the joint caused by rocking. Have fun.
   Best, Gary