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Mortise or Tennon First

AdamCisme's picture

Hi all,

     I am building a work bench. I am using resawn lumber for the main structure supports (legs and connecting boards in between them). I don't have a jointer, but after resawing them and sending them through the tablesaw they are very close to being square, but not perfect like a jointer would do.

   With that in mind I have two questions: 1) Would you cute the tennons first and then make the mortise to fit? I will be doing a combo of bandsaw and plane/chisels for the tennons and drill out and chisels for the mortises.

2) How big and deep would you make the tennons? Is there a general rule of thumb for sizing? The boards are 1" 3/8 by 3" 3/8  and the legs are 3 3/8 x 2 3/8.

Thanks!

Whether you think you can or think you can't, you're right!

hackmeister's picture

Mortice first (post #170974, reply #1 of 8)

Generally the mortice is cut first, mostly because it is easier to adjust the tenon to the mortice than the other way around.  Hand cut mortices can be trickey to get square and parallel, whereas tenons usually get cut right the first time around.

The easy way to get the sizing is to find a workbench plan similar to what you are building.  Looking at how they are constructed is a good design exercise.  Plus you will likely find some good ideas to incorperate into your bench.

In general, the rule is to make the mortice and tenon about a third of the thickness of the wood if equal thinkness, sized to your nearest chisel.  However with the size wood you are working on, 3/4 or 1 inch would be more than good enough, and 1/2 inch would propbably be fine for hardwoods like oak or maple as long as the stretcher isn't too long.  The long stretchers would need to be thicker though as they need to resist more racking.

For convenience, size the mortice to one of your (preferably beefy) chisels.  It makes cutting the ends of the mortice simpler and you can use the chisel as a width and parallel gage when you are cleaning up the sides.

For depth, if the joint is glued, go about 2/3 to 3/4 of the thinkness of the wood, unless you want to through mortice which is better yet.  Uusally if a joint  visually looks strong enough, it probably is.  Pinning the tenons with a dowel or wedging the through mortice is a good idea on a workbench, since they get beat on so much.

 If the boards are held in with a bolt (like on a bed) then 1/2 inch depth is fine, as the mortice only locates the board and resists twist.

if you are putting a mortice near the end of a board, you will need to do a haunched tenon or a bridal joint to avoid blowing out the end of the board while cutting or fitting the mortice.

Finally, if you are new to mortice and tenoning, definitely practice on some scrap first,.  Checking out a couple web videos would be worthwile as well; I am sure there are some good ones on this and other sites.

AdamCisme's picture

Thanks (post #170974, reply #2 of 8)

Thank you I really appreciate all the information. I did watch a few videos and they were helpful, but I hadn't thought of sizing it to my chisel so thank you for the tip. I think I will look at a few more as well before I dive in just to make sure I am not missing anything major (or helpful). Also, I had wondered when using a haunched tenon was appriate and I didn't realize what it was used for. So I will definetely keep that in mind for the future. 

The stretchers are fairly long as they run the length of the bench, from end to end they are 65", including the tenons. Also, the wood is not a hardwood so I think I will benefit all the way around from longer tenons from what you said. I had it in the back of my mind as a question also if pinning them may be a good idea, but wasn't sure when it was good to use them beyond asthetics, so now that you mentioned it I think I will take the time to do that as well. There will also be a cabinet inside with a set of drawers like the workbench in the newest video so my hope is that it will help with some of the racking force as well.

I have a few of the cutoffs from the legs still laying around so I think I will take your advise, as this will be the first mortice and tenon I have ever done, and give it a try on some scrap first. I cut the legs out of rough lumber that my uncle had and I am not in a hurry to ruin one and have to start all over from scratch!

Thanks again, I really appreciate the help.

Whether you think you can or think you can't, you're right!

hackmeister's picture

Growth rings (post #170974, reply #3 of 8)

Glad to be of help.  A work bench can be a great project to learn skills on.  It doesn't have to be perfect, only functional, and it is darned useful once you get it done.

One quick thing, on some softwoods like yellow pine and certain firs, the growth rings can be very hard, hard enough to deflect your chisel and even small drill bits (they naturally want to follow the softer wood in between).  Nothing wrong with using those woods, but something to watch out for.

RalphBarker's picture

Vidoes (post #170974, reply #4 of 8)

If you haven't already discovered them, Lie Nielsen has a bunch of useful videos on YouTube:

http://www.youtube.com/user/LieNielsenTo...

 

forrestb's picture

think about loose tenons (post #170974, reply #5 of 8)

This is exactly how I got started in woodworking: building my workbench using Tage Frid and James Krenov pictures for the design.  I used big dovetails, mortise and tenons and fingerjoints just so I learned how to do all.  I had a tablesaw, some chisels and a couple of planes.

I used planes and winding sticks to flatten the surfaces and control the thickness.  Whew! recalling the work I put in makes me tired.

If you have Forstner bits they will help reduce the tendency to follow the grain in softwood.  I hope that you have some means to guide the bits consistenly so your mortise sides are level.  If you don't you might consider pegging the joints during glueup.  The mortise and tenon depends on the long grain surfaces being close so the glue grabs the maximum surface area.

I have recently started to use loose, or slip, tenons.  The advantage is that all of your pieces are mortised and your slip tenons are all made at once to fit the mortise.  No need to handfit each tenon to its mortise.  Admittedly that fitting effort is instructive.

The downside is that you really need a jointer and thickness planer to make the tenons identical.

Good luck!  I have really enjoyed my workbench over the last, well, many years.

Forrest

AdamCisme's picture

Work bench (post #170974, reply #6 of 8)

Thanks for all the tips. I have done some woodworking off and on over the years, but this is the first time I have settled down to do it and have the place to set up shop. Just to get this project going I have had to set up my band saw to resaw, which involved new tires and the correct blade, a crosscut sled and now just finished a mallet so I can do the mortises. Then my brother got me some Narex chisels for Christmas so have been giving those a try.

I hadn't realized about Lee Valleys videos. I will add that to my mental list. And also about the growth rings in pine.

Whether you think you can or think you can't, you're right!

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BernieLeB's picture

good advise (post #170974, reply #7 of 8)

Adam - you have good advise on making the mt joint, but the meister forgot to mention one small detail he probably knows. Don't bottom out the tenon, if you cut it to the total debth of the mortise, shave off an 1/8 inch. This allows a place for the excess glue to go.

It's never hot or cold in New Hampshire... it's always seasonal

Routerman's picture

Continuous adjustability in (post #170974, reply #8 of 8)

Continuous adjustability in both of my routing fixtures.
As such it makes no difference whether I make tenons or mortices first.