Mortise for table leg.
#11
  
I am Building a table and would like to get opinions about the table leg mortise.

Would you cut the mortise as shown? Or would you cut it all the way to the end of the leg instead of leaving 1/4 inch of material there?

So.... leave 1/2", 1/4" (as shown in pic) or none???

These will be cut with a hollow chisel mortiser using a 1/2" bit. So ease of cutting would be the same for both ways.

The table will be 72" x 28" rough-sawn oak, fairly heavy.

Frankie


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#12
  Re: Mortise for table leg. by s9plus20 (I am Building a tabl...)
You might want to do a test piece and see if 1/4" of material left at the top is strong enough when you try to put the tenon in. Either way, I'm not sure I would leave the top of the mortise open (in which case you'd have more of a stopped groove and tenon than a mortise and tenon). It'll keep everything more in-place when you go to clamp everything during the glue-up if you have a mortise instead of a stopped groove. 


Also, I'm not sure how much glue strength you'd lose by going with a stopped groove...that top shoulder of the tenon is long grain, but its mating wall in the mortise is end grain (which soaks up glue like crazy). Still, you're not really gonna gain anything by doing a stopped groove and tenon over a mortise and tenon.
Near future projects:

-Curly Maple display case
-Jatoba and Quilted Maple dresser
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#13
  Re: RE: Mortise for table leg. by KingwoodFan1989 (You might want to do...)
Definitely do not cut all the way to the top of the leg.  I would leave 1/2 inch of material.   I like to think about the different forces involved, and design accordingly.  If you assume the tenon for the rail is in the mortise, and you pushed down on the top of the rail, it would try to force the end of the tenon up.  If you cut the mortise all the way to the top of the leg, more like a bridle joint, the only resistance to that force would be glue.  If you stopped the mortise 1/2 inch from the top of the leg, there is some meat to resist that force.  Of course, the force will not be straight down on the far end of the rail, but it is a similar force when you consider that when you move the table, the lower end of the leg will try to stay put, and as the upper end of the leg moves in one direction, the end of the tenon will again push on the upper end of the mortise.

BTW,  when cutting by hand with a mortise chisel, I normally cut the leg about 1/2 inch longer than actual, leave an extra half inch for the upper shoulder, then chop out the mortise, then go back and trim off the extra 1/2 inch - otherwise I risk blowing out the top end of the leg when chopping the mortise.
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#14
  Re: Mortise for table leg. by s9plus20 (I am Building a tabl...)
I was taught to make a haunched mortise for the sort of joint you are making. The haunch is a partial, stepped portion of the tenon at the top of the tenon.  It strengthens the joint, keeps it from racking, and importantly helps prevent the tenon from expanding and cracking the table leg.  If you are not familiar with this joint, here's what it looks like:




I've repaired many tables where a tenon has blown out the end grain of the leg because it was not haunched.  Worth the effort, I believe.


Greetings from Sunny (and incendiary) Southern California 

Greg Goldin
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#15
  Re: Mortise for table leg. by s9plus20 (I am Building a tabl...)
(12-07-2017, 10:06 PM)gregbois Wrote: Greetings from Sunny (and incendiary) Southern California 

Greg Goldin
Not to derail the topic, but are you doing okay where you are? I've seen the fires on the news the past couple days and it looks terrible. Stay safe.

To the OP in regards to Greg's suggestions, any joint that adds more long grain to long grain glue surface is gonna be stronger, so that haunch might be a good idea. I've never built a table anywhere near the size, but if I did I'd want as much strength as possible. Long grain to long grain surfaces that are properly glued can have more strength than the natural bond between wood fibers. In other words, the piece of wood can sometimes break before the joint comes apart.
Near future projects:

-Curly Maple display case
-Jatoba and Quilted Maple dresser
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#16
  Re: Mortise for table leg. by s9plus20 (I am Building a tabl...)
(12-07-2017, 07:29 PM)s9plus20 Wrote: I am Building a table and would like to get opinions about the table leg mortise.

Would you cut the mortise as shown? Or would you cut it all the way to the end of the leg instead of leaving 1/4 inch of material there?

So.... leave 1/2", 1/4" (as shown in pic) or none???

These will be cut with a hollow chisel mortiser using a 1/2" bit. So ease of cutting would be the same for both ways.

The table will be 72" x 28" rough-sawn oak, fairly heavy.

Frankie

I like how you have it now, going 1/2" would make for a different look, see more below on that. Going less?? What do you suppose will hold the tenon, yes of course glue, but you are dangerously close then to making a lap joint, instead of a M&T.

For me Mortise placement is dictated by a few factors.

Placement of the mortise will position the tenon, and likely the stretcher/apron. So placing it left, right, or centered will give it a different aesthetic, and depending on the look I want will drive that choice. As long as your leg is substantial enough to accept all positions, if not it will be centered, just due to meat left, will it be too thin, and possibly break? I am not much for moving the tenon cheeks left or right, because I like the parts to appear as light as possible, and using 3/4 thick stretchers you will weaken the tenon, by shifting it left or right. I have seen some that have done it this way. I do not, thinking it is a weaker joint. So I move the position of the tenon's insertion into the leg. Same applies for the leg if it isn't large enough to accept the offset mortise. So on light pieces I always center the mortise.

Size of the tenon is dependent on if it is for looks, strength, and weight bearing, or is it a combination of both? I tend to make my tenons as large as I can accept into the leg that is receiving it. Both in depth inserted, and width. Again if it would weaken either the leg, or the stretcher I will make the parts bigger. If I feel it is plenty strong for what purpose it will serve, you can go lighter on say a small table with a 10 ounce candle on it. A heavy large sized dinner table to seat 16, wide and thick legs, and 6/4 stretchers.

Using a rule of thumb of thirds works fairly well. So on a tenon at the end of a stretcher that is 3/4" thick, I'd take 1/4" off each side, leaving 1/4" wide tenon, going into a tight 1/4" mortise. You can do that backwards if you like, with the tenon slightly wider into a perfect 1/4" tenon, but you want it to fit snug enough that when you dry assembly you don't need 14 people to hold all the loose parts together. Again some people make them wider or smaller %, just keep in mind if you go too far you may weaken the joint.

Measure all of the holes after you make a test cut. You say 1/2" hollow mortise chisel bit. Make sure it is, many are actually metric, and a lot of them are just cheap, and it's kinda 1/2". Knowing for sure of your cut width before cutting is important.

Lots of test cuts as you go, and try to have all of your stock prepped with some extra pieces made in case of........

Also when you measure to make final length cuts before you cut tenons, make sure to add ++++ for whatever mortise depth you want to have, or your table just shrunk.

Cutting the tenon cuts into the end grain can be tricky on LONG pieces. I do them on a bandsaw, and I always have a roller, or work support out the length of the pieces, so I don't need to worry about having to hold a long piece up flat, and straight as I try to push it into the saw. That allows me to stand at the saw, and direct the cut, and determine the correct stop depth easily, rather than guessing where it is half way back the length of the piece. Trying to stand really tall pieces up on a TS are hard to do, and using a hand saw you may not be able to get into the position required to make a straight, and true cut, or have to do it on a ladder. Now to cut from the face grain over to your end grain cut line, you can easily do them with a sharp hand saw while the piece lies on a workbench.

When you mortise go leapfrog every other width, or slightly less is better then go back and cut just the small fingers left. Doing it like this keeps the cut from wandering which they tend to do if you stay in the cut and go repeatedly next door........ SHARPEN the chisels well before starting, and resharpen if the cut quality deteriorates. Remember you want a snug fit of your tenons for dry fit, and when you glue up I suspect snug tenons and glue will last a lot longer than loose tenons and glue, where some of the surface may have a gap, and no glue coverage.

FWW video with 3 things to get a better glue up

Something like this will help in that sharpening chore

Probably 16 things I'm not thinking of, because I'm not doing a M&T joint here. That is an oldfartola problem, can only remember when it becomes muscle memory doing the thinking. Also I answered, and went into some things you didn't specifically ask about. Possible you knew all of this, and just wanted a hey what do ya think from several people on what they like. Like I said before it is important to the look you want or like. If you did know all the other stuff , my apologies, but a lot of other people may read this post, and maybe some of this helped them understand some part of M&T's. An awesome joint, not used by many as they think them to be too difficult.
Worst thing they can do is cook ya and eat ya

GW
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#17
  Re: RE: Mortise for table leg. by KingwoodFan1989 ([quote='gregbois' pi...)
(12-07-2017, 10:20 PM)KingwoodFan1989 Wrote: Not to derail the topic, but are you doing okay where you are? I've seen the fires on the news the past couple days and it looks terrible. Stay safe.

To the OP in regards to Greg's suggestions, any joint that adds more long grain to long grain glue surface is gonna be stronger, so that haunch might be a good idea. I've never built a table anywhere near the size, but if I did I'd want as much strength as possible. Long grain to long grain surfaces that are properly glued can have more strength than the natural bond between wood fibers. In other words, the piece of wood can sometimes break before the joint comes apart.

Thanks for asking.  Luckily, the fires are not near my home.  The air is smoky, but not intolerably so.  I have good friends near Ventura, in Ojai, and they almost lost their home.  Fire fighters from as far away as Arizona have flown in and saved their homes from near certain perdition.  One cannot say enough for these courageous and honorable men and women.
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#18
  Re: RE: Mortise for table leg. by gregbois ([quote='KingwoodFan1...)
(12-08-2017, 06:47 PM)gregbois Wrote: Thanks for asking.  Luckily, the fires are not near my home.  The air is smoky, but not intolerably so.  I have good friends near Ventura, in Ojai, and they almost lost their home.  Fire fighters from as far away as Arizona have flown in and saved their homes from near certain perdition.  One cannot say enough for these courageous and honorable men and women.

Glad to hear everything's good! Hopefully the wind dies down, too!

Also, this thread has actually given me some insight into a current project. I was close to making the mistake of doing a tenon-and-groove rather than a mortise-and-tenon on a pretty integral part. Funny how that works out.
Near future projects:

-Curly Maple display case
-Jatoba and Quilted Maple dresser
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#19
  Re: Mortise for table leg. by s9plus20 (I am Building a tabl...)
Thanks for all the suggestions.

I ended up leaving 3/4" at the top.

I got some time to work on these Saturday.  I got all the mortises cut, along with all the tenons.

Frankie


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There are 10 kinds of people in the world, those who know binary and those who do not.
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#20
  Re: RE: Mortise for table leg. by s9plus20 (Thanks for all the s...)
Looks nice.  Also like the assortment of tools that you used in addition to the hollow mortiser -
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