Tenons, how many, how big? - Woodworking Talk - Woodworkers Forum
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post #1 of 19 Old 01-10-2020, 01:07 PM Thread Starter
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Tenons, how many, how big?

So I'm into my first actual project using real wood intended not for the garage :) It's a cherry end table, with a single drawer and tapered legs. Probably a pretty familiar design. I've got the top (22x28) glued up, and the aprons (8" wide) glued up, and today is leg (2x2) day. I'm thinking the mortices ought to go in before I do any tapering.

So in thinking about the mortices, I'm not sure on the size of them. For an 8" wide panel, should I have one long mortice, like 6"? Or two smaller mortices? Or one small one? I don't suppose this table will receive a bunch of stress, so maybe the answer is related to keeping the aprons straight and flat over time?

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post #2 of 19 Old 01-10-2020, 02:59 PM
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With boards that wide my first choice would be two mortise and tenons. Second choice, 1 six inch one.
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post #3 of 19 Old 01-10-2020, 03:09 PM
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It's been my limited experience that the more joints my projects have, the straighter overall my projects assemble. In the cabinets I've built, with lots of dovetails, and mortise and tenon joints, test assembly showed very square construction. It's pretty amazing how that works; that you can have slightly imprecise joints, but together it all evens out.

With that, I'd say you should create 2 mortise/tenon for your aprons.
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post #4 of 19 Old 01-10-2020, 10:44 PM
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I agree with the others, two should be made for such a wide joint.

Now, how do you plan on making mortises and tenons? It's quite easy to make the mortises with a shop made jig and a router with an up spiral bit and a guide bushing. The result is a very clean and usually accurately placed mortise of an exact width. This works so well that I suggest that you make mortises in both pieces where they will be joined together, and then make floating tenons to fit those mortises.

You can prepare the tenon stock using a table saw. Make the material nearly the correct thickness and then plane them to an exact thickness. Then as you need them, just cut them to width and length from the prepared stock. You don't need to make the ends round to match the mortise. The flat sides of the mortise and tenon need to be cut very accurately, because the quality of fit to the mortise sides to the tenon sides provides the strength when the joint is glued. Leave the half round ends of the mortise as a place for the excess glue to go. You don't need the tenon to fit into them. It's just a lot of extra work to round the ends of the tenon stock. Fit them to the flat sides of the mortise with a few thousandths for the glue and you will have a very strong joint. I made some chairs over 40 years ago this way that still have tight joints.

I gave up the mallet and chisel method of cutting mortises 50 years ago. I gave up the square chisel mortising machine 46 years ago. Save yourself a lot of grief and manual labor by making your mortises and floating tenons like I suggest. You will be very happy that you tried it.

I now use a Leigh FMT Pro for all of my mortise and tenon work, but I couldn't justify it until I was facing a job that required over 1600 mortise and tenon joints. I think I might still be working on that job if I hadn't bought the FMT. You can get nearly as good results using the method that I described above. It isn't quite as fast or as accurate, but it is very close, and way better than the mallet and chisel method.

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post #5 of 19 Old 01-10-2020, 11:07 PM Thread Starter
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Thanks for the input Charley. I had planned on making my mortices on my router table with an up-cut bit, and the tenons on my table saw. I've practiced this a couple times, with pretty good results, and my real concern is whether I can get all these cut in the right places, more than whether I can cut the tenons just the right width, etc. I have zero plans to get a chisel anywhere near this project :)

Interesting though, about making two mortices and a loose tenon to glue in. I guess that would be like the domino I hear so much about.

Dave
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post #6 of 19 Old 01-11-2020, 12:37 AM
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Dave

Go for it.
I too am strongly leaning with the 2 mortise.2 tenon crowd.
And, there are several ways to do both WITHOUT a chisel.

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post #7 of 19 Old 01-12-2020, 09:02 PM Thread Starter
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Mortices, and tenons - done!

Now on to tapering the legs. Ugh.
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post #8 of 19 Old 01-13-2020, 09:37 AM
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Here comes the monkey wrench - 2 joints will fight each other during the natural wood movement. With my MT joints, I cut my mortises with a router centering jig (not the table) using an up-cut bit. For an 8" joint, I would cut a 7" mortise leaving the ends round. As for the tenon, it would be a 6 1/2" and I would only cut the shoulders on my table saw. My router table handles the rest of it. I have a micro lift in my router table so I can dial in the precise thickness... if you don't have a lift, cut your tennons slightly proud and hone them down using a rasp or metal file.


Wood expands and contracts along its' width not its' length, not its' lengths. That includes the wood between 2 MT joints. The movement of the wood starts in the middle of the board and moves out in both directions and that is why I would not recommend 2 mt's. I glue the center 1/4 of the joint.

Its' never hot or cold in New Hampshire... its' always seasonal.
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post #9 of 19 Old 01-13-2020, 09:56 AM
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This link (Sawmill Creek forum) seems to have some good info. Read the entire thread.

https://sawmillcreek.org/showthread....-wood-movement

Geoff
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post #10 of 19 Old 01-13-2020, 10:11 AM
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Looking good!


Traditionally a haunched tenon at top, 1/4" shoulder at the bottom (this also alleviates the issue of seeing a gap)

Regarding the side aprons, I would offer for your consideration that since the apron is so wide, movement could possibly be a factor all depends on your climate zone. An excellent way to this is with drawbored pins -- no glue. (This was actually a very common way to build furniture way back when).

BTW I pin a lot of M/T joints even when glued. Arguably the strongest joint in ww'ing.

Robert
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post #11 of 19 Old 01-13-2020, 04:14 PM
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I have repaired literally well over a thousand chairs. Most of them were older chairs likely 80 years or more. Most of them with mortise and tenon joints, were just glue failures due to time. And most of them were hide glue. Easy repair. About the only time i would ever see a broken tenon is when someone ran a screw through it to fix it when it became loose.

A good amount of chair failures overall were due broken dowels. Probably built during the Great Depression.

Repairs today on modern furniture are more challenging. Usually the modern adhesives just dont fail - Too strong to fail. So the wood has to give. Same for modern repairs - once done properly, that's it for life, which is not always a good thing.

Most modern joints that fail are due to starved glue joints. The manufacturers use too little glue at times. My guess is that it saves them from minor cleaning up of the adhesive.

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post #12 of 19 Old 01-14-2020, 08:25 AM
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Originally Posted by Tony B View Post
Repairs today on modern furniture are more challenging. Usually the modern adhesives just dont fail - Too strong to fail. So the wood has to give. Same for modern repairs - once done properly, that's it for life, which is not always a good thing.
That's a good point I hadn't given a lot of thought to. Makes a good case for the use of hide glue or snot.

It sounds illogical, but would you advocate the use of weaker glue for items that get more stress, so they could be easily reassembled upon failure?

Geoff
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post #13 of 19 Old 01-14-2020, 11:34 AM
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Quote:
Originally Posted by AwesomeOpossum74 View Post
Quote:
Originally Posted by Tony B View Post
Repairs today on modern furniture are more challenging. Usually the modern adhesives just dont fail - Too strong to fail. So the wood has to give. Same for modern repairs - once done properly, that's it for life, which is not always a good thing.
That's a good point I hadn't given a lot of thought to. Makes a good case for the use of hide glue or snot.


With the suggestion of “ using a weaker glue” obviously as a method to try and avoid cracking /splitting of the wood components I would suggest hide glue as it is adequately strong enough for intended purposes and should disassembly be necessary down the road it is relatively an easy disassembky with a heat gun applied to the joint t as the hide glue reacts to the heat But it seems like the original post concerning an end table veered off track into chair leg assemblies. Joints that need to endure a lot of stress factor. This table will most likely have to be able to withstand the stress if a coffee cup and lamp-both at the same time!

It sounds illogical, but would you advocate the use of weaker glue for items that get more stress, so they could be easily reassembled upon failure?
With the suggestion of “ using a weaker glue” obviously as a method to try and avoid cracking /splitting of the wood components I would suggest hide glue as it is adequately strong enough for intended purposes and should disassembly be necessary down the road it is relatively an easy disassembky with a heat gun applied to the joint t as the hide glue reacts to the heat But it seems like the original post concerning an end table veered off track into chair leg assemblies. Joints that need to endure a lot of stress factor. This table will most likely have to be able to withstand the stress if a coffee cup and lamp-both at the same time!
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post #14 of 19 Old 01-14-2020, 12:00 PM
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Or someones feet if they so desire. I dont put my feet on furniture but lots of people.. There are also side stresses from bumps, people and pushing it around..

Sometimes even small children sit on or play on a coffee table. Packages temporarily get set on them.

We all dont live in museums.

Also note the type of joinery is every bit as important as the adhesive. The strongest glue in the known world will not prevent a joint from breaking. The difference being that the joint will break the wood and not adhesive.

And yes, I agree that hide glue is adequate as proven by the longevity of antiques before they fail. Keeping in mind, that they are used in concert with good joinery.

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post #15 of 19 Old 01-16-2020, 06:41 PM Thread Starter
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More progress! Got the legs tapered and a drawer made (for some reason I dreaded that, but it was more fun than I thought). Got a mongo 60 degree router bit to chamfer the underside of the top. A bit scary when I turned the router on, but all worked out. Made 4 passes to take off that much wood.
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post #16 of 19 Old 01-16-2020, 07:20 PM
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More progress! Got the legs tapered ...
They look nice. How did you do that?
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post #17 of 19 Old 01-16-2020, 07:31 PM
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More progress! Got the legs tapered and a drawer made (for some reason I dreaded that, but it was more fun than I thought). Got a mongo 60 degree router bit to chamfer the underside of the top. A bit scary when I turned the router on, but all worked out. Made 4 passes to take off that much wood.
Looks good... one word of advise.. put the sap towards the end or top or bottom when gluing up panels........Rebelwork
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post #18 of 19 Old 01-16-2020, 07:48 PM Thread Starter
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They look nice. How did you do that?
Thanks!

I made up a jig. It's specific to this taper, as you can see in the pic. Screw down the blocks and a couple L brackets, with the leg slanted off the side of a board. Then run it through the saw.
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post #19 of 19 Old 01-16-2020, 07:50 PM Thread Starter
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Looks good... one word of advise.. put the sap towards the end or top or bottom when gluing up panels........Rebelwork
Yep, I noticed that too, of course after I was done. For some reason while I was gluing them up, I couldn't even tell there was sap wood on the board. I just didn't watch carefully, this is the first time I did it.

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