Is this a good M-T joint?

[Dan Case LR]

I was playing with a design last night, trying to do something different with intersecting tenons. I doubt that I've created anything new here, but I've never seen one done this way and I'm curious of any of you have either seen or done this--and if there's anything stupid about the design. :)


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Thanks!

D.

[Jay Jolliffe]

Looks like it would work to me. It would give you more glue surface than 45ing the tenons in the middle.....Good idea

[Bob Lang]

It isn't commonly seen, but it is a good method. The red flag I see waving is at the top of the leg, too close for comfort and likely to break. Shoulder at the top should be about 3/4" to keep from breaking out the end of the leg.

Bob Lang

[Bill White]

It is a haunched thru tenon, and Bob is correct about the potential breaking.
Bill

[Jim Rimmer]

it isn't commonly seen, but it is a good method. The red flag i see waving is at the top of the leg, too close for comfort and likely to break. shoulder at the top should be about 3/4" to keep from breaking out the end of the leg.

Bob lang

+1 - damhikt :)

[Stephen Cherry]

The top would break. One thing to keep in mind, in my opinion, the mortise and tenon have been around since the dawn of civilization-- not to say that it can't be done, but it would be tough to improve.

[Jerome Hanby]

I've seen similar joints in some mission style furniture, specifically a Prairie Settle. Think the one Norm built had a similar joint.

[Lee Schierer]

Unless you really want the ends of the tenons sticking out where they will show, I would shorten them so that you have face grain left on the surfaces that show. You aren't gaining any strength with the added length so it will be okay to shorten them to improve the appearance.

[Prashun Patel]

That looks like a cool joint. Pls. post pix of the real stuff if you move forward with it.

[glenn bradley]

If the aprons are to be that high I would use a shorter tenon and miter them. If you still want the look, false tenons would get that for you without the weak structure at the top of the leg that you show.

[Jerome Hanby]

That's a nifty idea. Does it actually had some significant strength over just making the tenon shorter (as short as the short side of the miter)?


If the aprons are to be that high I would use a shorter tenon and miter them. If you still want the look, false tenons would get that for you without the weak structure at the top of the leg that you show.

[Kent A Bathurst]

Claim jumping Dan a little bit here.......

I made a table base with mitered tenons for the upper rails into the legs, but with the top edge of the rails extending straight through to the tops of the tenons......which means the top edge of the tenon was exposed in the leg top - the mortises were open to the sky. Glued, of course, and also pegged [just pegged, not drawbored] - 2 pegs per tenon. The tenons are 2-1/4" tall, 2" deep into the leg, and about 3/4" thick [into 3" x 3" legs].

The table base has upper and lower end rails, upper side rails, and a stretcher between the lower side rails, centered - I didn't see how there could be any more than nominal racking force on the joints. I couldn't see any way that joint would fail. :confused: There is a lot of long-grain glue surface, and the pegs for both insurance and aesthetics to match the rest of the joinery [not that anyone will crawl under the table top and look up to notice......but I know they are there. ;)]

Please feel free to rain on my parade, if you've got some different insight.

[Jamie Buxton]

.... The red flag I see waving is at the top of the leg, too close for comfort and likely to break...

I've seen this concern before, and I don't quite understand it. What holds a mortise and tenon joint together is glue. The top of the leg might split while you're cutting the mortise, after you've glued the joint together, it should be completely solid. And if you cut the mortise with a not-very-stressful method like a plunge router or a hollow chisel mortiser, there really shouldn't be any splitting force applied to the top of the leg.

[Gary Kman]

With full height, mitered end tenons, the farther the rail is located toward the outside of the leg the longer the tenons are. The most glue area where it counts. Your's appear to be centered.

[Bob Wingard]

If the aprons are to be that high I would use a shorter tenon and miter them. If you still want the look, false tenons would get that for you without the weak structure at the top of the leg that you show.

Hey Glenn ... I think you are overlooking an opportunity for gaining strength if you simply miter those ends. Try cutting the tenons full length, then use either dovetails or box joints at those ends to make a totally concealed, super strong joint. Works great.

[Kent A Bathurst]

With full height, mitered end tenons, the farther the rail is located toward the outside of the leg the longer the tenons are. The most glue area where it counts. Your's appear to be centered.

More or less. That didn't really answer my question, however.

Are you saying I'm not good, but would have been had I moved it farther out to get a longer glue face? If the tenons were the same dimension, but the legs had been, say 2-1/2" x 2-1/2", would that have been better?

Or, are you saying that the right way is to make it as long as possible, given the dimensions on the mortise part? In that case, my question changes to: Given 5/4 [1" net] rails into 3" x 3" [net] legs, what is the preferred length of the mitered tenons?

I understand your words, but I'm missing the point, I guess. :confused:

Thanks

Kent

[Dan Case LR]

Thanks for all the comments and insight, guys. Now that I think about it, I probably should have mentioned where I'm contemplating using this joint.

It's for a workbench. The design is based loosely on the Fine Woodworking GSIW bench, which is built from dimensional lumber and MDF with truss rods and dowels. I modified their design a little, of course--cleaned it up a little, tweaked it here and there and moved the vise to the end--and was getting close when I began to consider springing for hardwood for the base instead of construction lumber. That led me to question the truss rods and dowels. Not that they wouldn't work, but it just didn't feel right for a hardwood base to be bolted together with threaded rods. I began playing a little, and what you see is one of the things that resulted.

The legs are still 3 1/2" square, and the stretchers are still 1 1/2 x 3 1/2. The top surface of the legs and top stretchers will be supporting 3 or 4 layers of 3/4" MDF, which will somewhat mitigate the risk of the mortise breaking--however. your note on that is well taken and it's an easy thing to correct at this stage.

This won't be a "showpiece" bench, so if the truss rods are really a better technique I could still go that way. This bench will be a big step forward, replacing a swayback 5 foot folding table that's served well for years and is ready for the big dumpster in the sky.

Now that I've filled in the information gap, any further thoughts?

D.

[Jim Matthews]

Haunched as shown, drop a dowel right through the middle. Just a little glue at the very top of the dowel, to keep it from working free.
The Dowel could stand proud, to act as a locator pin for the top. This crossgrain orientation would resist racking forces along the top rails.

Alternately, drill straight through the works, and put a brass insert at the bottom. You could then tighten the works with a heavy bolt.
I'm no fan of permanent fixtures on workbenches - you may need to move it someday and this joint won't be easy to reverse.

I'm wondering if you might incorporate a Japanese Timber frame style lock in this? Figure 189 (http://www.timberframe-tools.com/reference/woodwork-joints/mortise-and-tenon-joints/) alludes to this...

[John Coloccia]

Not that they wouldn't work, but it just didn't feel right for a hardwood base to be bolted together with threaded rods.

That's quite an excellent and sturdy way of building a workbench. The only thing I would really even consider over that is a draw bore mortise and tenon. The simplicity and durability of the threaded rods, along with the ability to take it apart easily, really makes them somewhat of a slam dunk in this application.

That said, were I to build a new bench today, I would seriously consider using with Noden adjustable bench legs. Once you understand how the system works, you'll see that it can make quite a heavy and sturdy bench. Maybe you'll be able to find someone in the area that has one for you to see.

[Gary Kman]

I don't see GSIW in the abbreviation so I don't know what it is. I can't imagine a workbench built as a parsons table without stretchers midway up the legs. Why would anyone want to? The rigidity with stretchers where they are normally located on a bench would likely be an order of magnitude greater than the parson table you are contemplating. The only joints that I could imagine would hold up in the design you propose would be cast or welded.

[Jerome Hanby]

I don't see GSIW in the abbreviation so I don't know what it is.

Getting Started In Woodworking. A FWW book, I believe...

[Gary Kman]

More or less. That didn't really answer my question, however.

Are you saying I'm not good, but would have been had I moved it farther out to get a longer glue face? If the tenons were the same dimension, but the legs had been, say 2-1/2" x 2-1/2", would that have been better?

Or, are you saying that the right way is to make it as long as possible, given the dimensions on the mortise part? In that case, my question changes to: Given 5/4 [1" net] rails into 3" x 3" [net] legs, what is the preferred length of the mitered tenons?

I understand your words, but I'm missing the point, I guess. :confused:

Thanks

Kent

Didn't exactly sort out your question and was addressing the original poster. Many excellent books on woodworking and joinery out there so we don't have to re-invent the square wheel. Modeling different joints and wiggling them around tells me a lot.

[Kent A Bathurst]

.......... was addressing the original poster..........

Oooops. :o

Never mind. Carry on as you were. ;)

[Dan Case LR]

Getting Started In Woodworking. A FWW book, I believe...

A video series on finewoodworking.com. Might be a boo too (Since that's what Taunton does), but I've never seen it.

D.

[Dan Case LR]

That said, were I to build a new bench today, I would seriously consider using with Noden adjustable bench legs. Once you understand how the system works, you'll see that it can make quite a heavy and sturdy bench. Maybe you'll be able to find someone in the area that has one for you to see.

I've never seen one in person, but I've looked at the Noden system a time or two online. It's really a sweet concept, but not for the shallow-of-pocket. OTOH, I showed the demonstration video to my wife this morning and she said, "After you finish with the one in your shop, I want one of those for my sewing room." There may be hope. :)

D.