Miller dowels for knock-down M&T joints?

[Phil Stone]

I'm building a sewing/work table for my girlfriend, with three goals: it must be sturdy, decent-looking (but not fine furniture), and able to be disassembled. I thought at first of drawboring the M&T joints, but now think that that's not a very knock-downable joint. Drilling out the drawbored dowels would probably destroy the offset. Now I've been thinking about using Miller dowels, dry, to pin the joints. I'm hoping the stepped design of the Miller dowels will provide enough hold to keep the joints together, but am not so sure about that. Opinions?

[Jim Koepke]

My first consideration would be toward how this will be stored when "knocked down."

Steve Ramsey on Wood Working for Mere Mortals built a craft table into a wall cabinet. It would even be possible to build storage into the doors. His uses hinges and braces.

http://woodworking.formeremortals.net/2015/06/drop-down-table/

jtk

[Phil Stone]

My first consideration would be toward how this will be stored when "knocked down."

Steve Ramsey on Wood Working for Mere Mortals built a craft table into a wall cabinet. It would even be possible to build storage into the doors. His uses hinges and braces.

http://woodworking.formeremortals.net/2015/06/drop-down-table/

jtk


Hi Jim,

It is aimed more towards being able to move it (get it out of the room) if necessary. The top is 4' X 8' -- I neglected to mention the size. Here's a jpeg from SketchUp.

329187

[Phil Stone]

I don't know if it's rude to reply to one's own thread, but the idea of bed bolts just occurred to me. Part of me wants an all-wood solution, and there 30 or so stretcher joints that will need to be knock-down, so the hardware cost might add up. Talk amongst yourselves while I research that. :)

[kent leben]

have you considered tusk tenons? Not sure how practical it would be if you had thirty of them though.

[Phil Stone]

have you considered tusk tenons? Not sure how practical it would be if you had thirty of them though.


Yes, I did, but then realized that the lumber I had bought and dried wouldn’t allow stretchers longer than 48”!

[Mike Brady]

Miller dowels would add nothing and can only be removed from one side of a through joint. Are those even made any anymore? What about those eliptical metal things that IKEA uses in their stuff? I would do tusk tenons.

[Tony Zaffuto]

I use Miller Dowels frequently, but don't think I would consider them for a knock down joint.

[Phil Stone]

Miller dowels would add nothing and can only be removed from one side of a through joint. Are those even made any anymore? What about those eliptical metal things that IKEA uses in their stuff? I would do tusk tenons.

I was hoping, naively, that Miller dowels would hold themselves in somehow (like a regular pinned joint but with extra grip because of the steps). I guess I didn’t think that through very logically — they could just back themselves out without glue. As far as one-sidedness goes, most of the joints would have access from two sides.

It’s beginning to look like bed bolts are the only viable solution. As I said, my design and amount/length of dried lumber won’t permit tusk tenons.

[Warren Mickley]

I have taken many frames apart that were put together with pinned mortise and tenon. The key is to use tapered pins (which are traditional). You can knock the pins out from the back side, using a small pin and a mallet. You might even leave the pins a little long on the back side, easier to hit out. Because they are tapered, they loosen up quickly when they have moved about 1/2 inch.

[Jim Belair]

It’s beginning to look like bed bolts are the only viable solution. As I said, my design and amount/length of dried lumber won’t permit tusk tenons.

You don't have to buy "bed bolts", just a bolt and a nut in a large hole will work.

[Allan Speers]

I don't know if it's rude to reply to one's own thread, but the idea of bed bolts just occurred to me. Part of me wants an all-wood solution, and there 30 or so stretcher joints that will need to be knock-down, so the hardware cost might add up. Talk amongst yourselves while I research that. :)


That's what I was thinking.

Any kind of joint that can just be knocked apart would probably not be that safe to use when assembled. Especially not over time, and especially not when supporting a motorized thingy with sharp needles moving about.

[Pat Barry]

Just a thought, not knowing how far you want to take this table 'down'. I would make the three leg assemblies and then use 1/2 lap crossrails (top, middle, bottom) and bolt those crossrails in place at the 1/2 lap joints.

[Max Neu]

What if you made it shorter,would that allow you to turn it sideway's to get through the door?Then you could add a top piece to get back to the finished height.I try to avoid knock down joints as much as possible,unless there is no alternative.

[Phil Stone]

Just a thought, not knowing how far you want to take this table 'down'. I would make the three leg assemblies and then use 1/2 lap crossrails (top, middle, bottom) and bolt those crossrails in place at the 1/2 lap joints.


I *am* thinking of making the leg assemblies solid; the crucial thing is to be able to take apart the stretchers, as you have discerned. I like your idea of half-laps, bolted. I'll think on that.

[Phil Stone]

You don't have to buy "bed bolts", just a bolt and a nut in a large hole will work.


True, but these are not too expensive, and look nice to boot: http://www.amazon.com/gp/product/B006ZLKVU2/ref=ox_sc_sfl_title_2?ie=UTF8&psc=1&smid=A8JNC38BPE91T

[Phil Stone]

I have taken many frames apart that were put together with pinned mortise and tenon. The key is to use tapered pins (which are traditional). You can knock the pins out from the back side, using a small pin and a mallet. You might even leave the pins a little long on the back side, easier to hit out. Because they are tapered, they loosen up quickly when they have moved about 1/2 inch.


Warren, would you consider those frames to be tight before you took them apart? I mean, had any of the pins loosened themselves?

[Reinis Kanders]

How about tension rods. Plow a grove for 1/4" all thread. Could be quicker than bed bolts, not sure about cost.

[Allan Speers]

If the top were made to overlap the leg units with a recessed apron, you might be able to fit small phenolic knobs underneath. They'd be out of the way and not too visible.

You might even be able to make the knobs out of wood. Heck, if you want it super-organic, you could even theoretically cut threads into long, thick hickory dowels, slide them through the legs assemblies and top-apron, then tighten with the wooden knobs. Easy to take apart, and kind of special, too.

Make the connecting faces in some way that the legs can't rack. (Maybe a guide dowel above each knob)

[Patrick Chase]

Hi Jim,

It is aimed more towards being able to move it (get it out of the room) if necessary. The top is 4' X 8' -- I neglected to mention the size. Here's a jpeg from SketchUp.

329187

One thing you might consider is orienting the middle tier of stretchers along diagonals (for example lower-left->upper-center and lower-right->upper-center)

With everything at 0 and 90 like that you're going to have to deal with racking loads on the joints - the beauty of diagonals is that they turn racking into tension/compression, and that gives you a wider design space for the knockdown joints.

[Warren Mickley]

Yes the pins will stay tight. I have tapered pinned tenon construction on my pole lathe; In addition to using it in the shop I have taken it to festivals more than 40 times since 1981, still using the original pins. It is helpful if the pins protrude a bit front and back. Just 1/8 protruding at the front gives you some leeway to tighten the joint after multiple moves.

Patrick mentioned racking. I would recommend a deeper apron, like three or four inches which would help with racking. A stretcher and a wide apron is more helpful than the three rails pictured. Also there is no need to have the base be as large as the top. Having a base say 42x 70 would be adequate and also allow appliances to be clamped to the edge. This would allow you to makes tusk tenons, probably the easiest joint to disassemble.

Also consider that not all your joints have to come apart to move the table. You could have the front frame, the back frame, and a pile of connecting rails and none of these would be more awkward to move than the top itself. I had a work table years ago that had two end frames (each had four pieces tenoned and pinned) and four long stretchers with tusk tenons, two in front two in back. I never took apart the two end frames. When disassembling mark everything, even wedges and pins, or put the pins back in the posts after removing the tenons so you don't mix them up.

[glenn bradley]

There is always that old "back to the drawing board" approach. . . consider a sheet goods / tusk tenon hybrid solution?

329202

The base could be made more interesting with simple cut outs.

329203

The "style" could be drastically changed depending on the cutouts, square, round, free-form,

[Alan Schwabacher]

A dovetail wedged tenon is very solid, all wood, does not require an extra long tenon, and easily taken apart. It works well for workbench leg stretchers, so should be fine in this case.

Here's an image borrowed from learningwoodworking.wikispaces
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcS-CZx7ntbJc8XuAObqE0S0JnIIa5pjxhMBlMNQTbpLb0nYJcYM (https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcS-CZx7ntbJc8XuAObqE0S0JnIIa5pjxhMBlMNQTbpLb0nYJcYM)

[Patrick Chase]

Patrick mentioned racking. I would recommend a deeper apron, like three or four inches which would help with racking. A stretcher and a wide apron is more helpful than the three rails pictured.

Yep, an apron provides its own diagonal support, and looks a lot nicer than diagonal stretchers. I'd assumed the OP was using thin stretchers to minimize weight.

[Patrick Chase]

There is always that old "back to the drawing board" approach. . . consider a sheet goods / tusk tenon hybrid solution?

329202

The base could be made more interesting with simple cut outs.

329203

The "style" could be drastically changed depending on the cutouts, square, round, free-form,

I made my son a quick and dirty workbench like that, except using hinges instead of M&T joints to attach the side panels to the back. I also didn't bother cutting openings in it. The hinges on one side are offset using a spacer strip, so that the entire back + sides assembly folds flat to 3X the thickness of the plywood (the portions of the side panels in front of the hinges are more than half the width of the back, so they must fold on top of each other).

I added a front apron that attaches to the sides via loose edge laps, and the top has vertically tapered cleats that bias the sides, back, and apron outward when the top is pushed home. The tapered cleats add a lot of rigidity as they take up any play in the hinges and edge laps, and also provide resistance to racking about the vertical axis.

No Pat, no pictures. This one was definitely carpentry, not woodworking (though I did hand-cut the edge laps and hand-plane the cleat tapers :-).

[Phil Stone]

Yep, an apron provides its own diagonal support, and looks a lot nicer than diagonal stretchers. I'd assumed the OP was using thin stretchers to minimize weight.


I kept the apron at 2-1/2 inches to maximize leg clearance. She wants to use the table both standing up and seated at a high stool. Here’s a drawing without the top, and I’ve worked a few changes since yesterday, but it’s basically the same:

329222


I understand what you’re saying about deeper aprons being an effective way to fight racking, but haven’t I compensated for that with the numerous stretchers? Seems like it should be a rigid box if all joints are reasonably tight. Also, diagonal stretchers are out, as the lower two tiers of stretchers will actually be shelving.

By the way, thank everybody so much for all the excellent input and ideas.

Edit: ignore the through-tenons showing in the above picture. They're left over from earlier ideas, and I haven't totally cleaned up the joinery in the model yet.

[Patrick Chase]

I kept the apron at 2-1/2 inches to maximize leg clearance. She wants to use the table both standing up and seated at a high stool. Here’s a drawing without the top, and I’ve worked a few changes since yesterday, but it’s basically the same:

329222


I understand what you’re saying about deeper aprons being an effective way to fight racking, but haven’t I compensated for that with the numerous stretchers? Seems like it should be a rigid box if all joints are reasonably tight. Also, diagonal stretchers are out, as the lower two tiers of stretchers will actually be shelving.

By the way, thank everybody so much for all the excellent input and ideas.

Edit: ignore the through-tenons showing in the above picture. They're left over from earlier ideas, and I haven't totally cleaned up the joinery in the model yet.

The way to think about this is to imagine that all of your members are joined by hinges or ball joints, which hold the pieces together but don't provide any resistance to rotation. Now imagine that somebody pushes the upper-left corner to the right. Obviously the whole thing will fall over to the right. It doesn't matter how many horizontal or vertical stretchers you add or how strong they are, the outcome will always be the same. What that should tell you is that all of your design's resistance to racking is coming from the joints and none from the stretchers. That's what struck me when I posted. While that's obviously workable with the right joints (just look at wooden chairs) it may limit your choice of knockdown solutions a bit.

Now repeat the same thought experiment, but imagine that there's an additional diagonal member running from the lower-right corner to the upper-left corner. Now when somebody pushes on the upper-left corner they'll cause that member to be loaded in tension, and the structure will not tilt. The structure now resists racking even if the joints do not.

Clearly a diagonal that runs all the way across like that is overkill, unless you're trying to optimize strength-to-weight. An apron as Warren suggests is a nice, traditional compromise.

[Allan Speers]

Re the racking:

This is why I mentioned using a deep apron and maybe adding guide dowels at the top, with the fasteners near the bottom of the apron. If the tolerances are good, and the dowels extend deep enough into the apron, that should eliminate racking.

I think. :o

---------------

I like Glen Bradley's concept, too. If you added two longitudinal stretchers on top, connecting the outside edges of the two end pieces, that would probably be rock-solid.

[Phil Stone]

Re the racking:

This is why I mentioned using a deep apron and maybe adding guide dowels at the top, with the fasteners near the bottom of the apron. If the tolerances are good, and the dowels extend deep enough into the apron, that should eliminate racking.

I think. :o

---------------

I like Glen Bradley's concept, too. If you added two longitudinal stretchers on top, connecting the outside edges of the two end pieces, that would probably be rock-solid.


Allan, I'm having a hard time picturing what you're describing here, but it sounds intriguing. Can I bother you for a sketch or example?

[Allan Speers]

Allan, I'm having a hard time picturing what you're describing here, but it sounds intriguing. Can I bother you for a sketch or example?

I don't have any sketchup type applications. Maybe I can hand draw something later & scan it. I'll try, when I have time.

[Allan Speers]

Well, I warned you!

329310

The knobs could go on the outside, of course, and then both the threaded rod and the dowel would be part of the apron. That would make more sense, but the above way hides the knobs.

Instead of dowels, you could use metal rod + bushings in the leg sections, for less wear.

You could even make the apron twice as deep, for extra stability, and then have those two long apron sections on hinges, so they swing up for easier transport.

----------------------------------

- but I still like Glen's idea, for its simplicity.

[Phil Stone]

Well, I warned you!

329310

The knobs could go on the outside, of course, and then both the threaded rod and the dowel would be part of the apron. That would make more sense, but the above way hides the knobs.

Instead of dowels, you could use metal rod + bushings in the leg sections, for less wear.

You could even make the apron twice as deep, for extra stability, and then have those two long apron sections on hinges, so they swing up for easier transport.

----------------------------------

- but I still like Glen's idea, for its simplicity.



Nice, Allen. Thanks for getting out the drafting equipment. :cool: I see what you're getting at, and I like it. More thinking required...

[Patrick Chase]

Well, I warned you!

329310

The knobs could go on the outside, of course, and then both the threaded rod and the dowel would be part of the apron. That would make more sense, but the above way hides the knobs.

Instead of dowels, you could use metal rod + bushings in the leg sections, for less wear.

You could even make the apron twice as deep, for extra stability, and then have those two long apron sections on hinges, so they swing up for easier transport.

----------------------------------

- but I still like Glen's idea, for its simplicity.

If you're going to bolt I'd just do what Ikea does (I'll probably go to "Neander H*ll" just for thinking that thought) and run the bolt down the middle, with a guide dowel on either side to prevent the apron from twisting. If you do that then the dowels can be short and skinny since they don't have to carry any bending loads.

[Patrick Chase]

If you're going to bolt I'd just do what Ikea does (I'll probably go to "Neander H*ll" just for thinking that thought) and run the bolt down the middle, with a guide dowel on either side to prevent the apron from twisting. If you do that then the dowels can be short and skinny since they don't have to carry any bending loads.

Oh, and put these in the Apron (from the back of course) so you won't need any knobs: http://www.leevalley.com/US/hardware/page.aspx?p=44238&cat=3,43576,45375,44238

For the record, I deny ever having used any such thing. Except when I had to. And when I was in a massive hurry.