Loose tenon joinery

[Derek Cohen]

I made this bed for my wife and I about 30 years ago, borrowing from plans in Woodsmith magazine (link here, if interested: https://www.woodsmithplans.com/plan/heirloom-cherry-bed/). (https://www.woodsmithplans.com/plan/heirloom-cherry-bed/)

https://www.woodcentral.com/home/uploads/2022/11/441_20221106.png



This is solid Jarrah, with the lower rails 30mm thick and 150mm high.
Joinery for the bedhead and tailboard is mortice-and-tenon (side rails use mechanical fasteners) ...

https://www.woodcentral.com/home/uploads/2022/11/820_20221106.png

https://i.postimg.cc/RCfDNNtK/2.jpg

I have a memory of building this in two weeks. My wife was visiting her mother, and I wanted to surprise her on her return. The slats all morticed and anyone who has fitted a construction like this will share the nightmare it was. There I was, the night before (working in the livingroom where there was space), fitting slats into mortices and trying to pull everything together with all the clamps I had. The parts would stick, and ... oh, the despair. But it came together in time.

I vowed never again to build a bed like this. But of course I did. Just one.

Now I want to build two single beds, also in Jarrah, which will be a simpler construction. Just a frame (rails) morticed into legs (in the same way as the bed above). That is, the head- and tail ends will be mortice-and-tenon, with the sides connected mechanically. One change with the the size of the rails: still 30mm thick, but now 125mm high. A little lighter looking.

The posts are likely to be 60x60mm square and will run about 10mm above the sides/rails.

Here's the issue: I have some Jarrah, but the ends will not be long enough to use mortice-and-tenons. I shall need to use loose tenon joinery. (And, no, I am not going to purchase more for the length - Jarrah like this is hellishly hard to find and Expensive!).

With 30mm thick boards, the 1/3 Rule applies and so the mortice and the tenon are both 10mm wide. Agree?

But now here's the issue: how deep into the rail does one make the mortice to support the loose tenon? The posts will have 40mm deep mortices for the end rails.

The plan is rout out the mortices for the loose tenons. The ends of the rails offer a challenge in that they are about 940mm, which runs 130mm above my bench. I could deal with this by making a small table to support the router.

The alternative is to make the 10mm mortices with a Domino 500 (which would be easier to start the mortices since the boards would be horizontal owing to their length). I do not plan to use dominos to join rail and post, however, as I do not see the dominos as strong enough (too narrow), even if three are placed alongside each other. Your thoughts here?

The other issue with the Domino is that it has a maximum 28mm depth of cut. It this too shallow to support a loose tenon (in single beds)?

Regards from Perth
Derek

[Keegan Shields]

Derek,

I used a Domino 500 and 10mm loose tenons to assemble a full sized solid maple door with a stain glass panel in it few years ago. No sign of sagging yet.

With a bed that has slats under the mattress which prevent racking of the frame, I think 10mm loose tenons will be fine. As I’m sure you know, Dominos/loose tenons/tenons resist sheering forces really well - which should be the majority of the force applied on a bed.

The only time I’ve had a loose tenon fail is when it was too large for the rail (my mistake), or when there were pulling (tensile?) forces applied to it.

Beautiful bed by the way!

[Andrew Hughes]

My thoughts it will be fine.
The loose tenon will be in the long grain of the rail? It will never come out after it’s glued in
Good Luck Derek

[Kevin Jenness]

I think in that situation three or four 10mm dominos would be ok as there is not a lot of racking stress across the end frames. As you seem to be on the fence though, you could make deeper mortises with a plunge router by clamping blocks flush with the rail ends to provide a more stable support. I would sandwich a piece of 30mm material between two thicker pieces to make a "U" for easy clamping. I would probably make two mortises about 45mm long and as deep as your tooling allows.

[Jim Becker]

I used the D700 and 14mm Dominos and 14mm connectors for the bed project a did a couple years ago for a client. Uber-strong.

[Malcolm McLeod]

With 30mm thick boards, the 1/3 Rule applies and so the mortice and the tenon are both 10mm wide. Agree?[/COLOR]

But now here's the issue: how deep into the rail does one make the mortice to support the loose tenon? The posts will have 40mm deep mortices for the end rails.

The plan is rout out the mortices for the loose tenons. The ends of the rails offer a challenge in that they are about 940mm, which runs 130mm above my bench. I could deal with this by making a small table to support the router.

The alternative is to make the 10mm mortices with a Domino 500 (which would be easier to start the mortices since the boards would be horizontal owing to their length). I do not plan to use dominos to join rail and post, however, as I do not see the dominos as strong enough (too narrow), even if three are placed alongside each other. Your thoughts here?

The other issue with the Domino is that it has a maximum 28mm depth of cut. It this too shallow to support a loose tenon (in single beds)?

Regards from Perth
Derek

I have used a few hundred Dominoes and never been able to ‘disassemble’ any such joint built with 8x22x50mm (Festool beech) Dominoes. And I tried. The rail/stile fails first. (I did a bulk purchase of the 8x22x50, so tend to design around it :: Scottish frugality.)

Mortises are 25mm deep in 95% of my installs; I’ll occasionally use 15mm depth to allow for cross-grain installs in 3/4” nom. material. For furniture use - or things other than entry doors and such highly leveraged constructions - 8mm thickness is probably plenty IMO, but 10mm will give you that much more margin.

Don’t forget you can cut a single mortise via multiple DF 500 plunges and make your own loose tenon stock to fit, in the width & material of your choice.

[John TenEyck]

The 1/3 rule was true when mortises were cut by hand, but I use thicker loose tenons now that I cut the mortises with a router. There's no danger of blowing out the sides of the mortises like there is when hand chiseling. I'm positive 10 mm thick Dominos are strong enough for the bed frame, but if you have the ability to cut thicker ones I would. What's the next larger size, 14 mm? Perfect if you can cut them. If not, don't worry about it. Put in as many 10 mm ones as logically fit and sleep well. As for the depth, the rule of thumb is 3X the thickness, so for a 10 mm Domino you would ideally make the mortise at least 30 mm deep. But again, these "rules" were developed for hand cut joints. Cutting a mortise with a Domino or router leaves a nice consistent and smooth wall so a well fitted tenon develops maximum strength when glued, as evidenced by Malcolm's comment about 25 mm deep being sufficient.

As for cutting them, use a Domino if you have one. If not, make a temporary (or permanent like I have) horizontal router mortiser and you can cut mortises in the end of boards of almost any length. If I were doing your project, I would cut 1/2" x about 3" wide x 2" deep mortises in the ends of your 125 mm (4.9 inch) rails.

John

[Jim Dwight]

I suspect that tenons an inch into the piece will work but I would much rather have them at least as deep in both pieces. I have the big domino machine so I can go 2 3/4 inches deep. I would also prefer a 12mm tenon. I saw a test somewhere that tested the 1/3 rule and the joints were stronger with tenons a bit thicker. It might have been by Mathias Wandel. But if 10mm tenons 25mm deep is the best you can reasonably do, I think it will work. I would make them as wide as the plans call for, however. I think using little pre-made domino tenons causes domino joints to get a bad reputation. It is very easy to make your own loose tenons any width you need. I do not buy domino tenons, I make them. Good use of scrap. I am also retired, however.

I have made 3 beds of the style you picture. I agree getting the slats in is a pain. I left the mortises open on the top once and tapped them in after I glued the frame of the headboard and footboard up. I had little tenons on the other end and mortises for them to go into. What I did on the last one was far easier. I got the idea from a Wood plan for a crib I built. You just plow a dado in the cross pieces of the headboard and footboard the width of the slats and then use little spacers to position the slats after everything is glued up. You have to put the slats in then the spacers to have space to tilt the slats in. A dab of glue and a pin nail or two secure the spacers. TONS easier. It's a little tricky to figure out the length of the spacers but if you have to cheat a little on the last one or two it is not very noticable. I had the spacers stick up about 1/8th just because it's easier than trying to get them perfectly flush.

The oldest of the 3 beds is at least 20 years old, might be 30. It is oak and my son and his wife sleep on it now. Another was a wedding present for my daughter and son in law a little over 11 years ago. It is cherry as is mine, made in 2018. Only mine used domino joints, the others were all traditional mortise and tenon. Doesn't matter, they all work fine.

[Albert Lee]

Derek, I build bed all the time (single, double, long single, king single, even queen) and as you know my operation is semi commercial, the standard 100mm long x 14mm domino will suffice in situation like this.

[Derek Cohen]

I have planned on either 10mm thickness for the loose tenon, in which case I will start the mortice with the Domino, and then deepen it with a drill. Or make the mortice completely with a router as I have a 1/2” diameter spiral bit deep which is enough (past experience showing me that it is possible to go a little wider in the mortice when using a router). The traditional side of me wants to go with 10mm.

I have also roughed out the loose tenons from the same Jarrah board. This was necessary as I expected their total length to be greater than a domino. The question I have is how deep does the loose tenon need to be anchored in the stretcher? Linked to this, would it aid strength to lock the anchored end with a pin?

Regards from Perth
Derek

[Jim Becker]

10mm/.375" spiral end mills are readily available so you can avoid the larger .5" mortise if it doesn't work for you. I actually keep a piece of .375" tooling with a 1.75" LOC (length of cut) for certain CNC things like cutting out guitar bodies or thicker charcuterie boards and that can also be used as a "mortise monster" if I needed to.

[Derek Cohen]

Jim, thanks. I have been searching for a 10mm spiral bit. The ones I find are end mill bits for CNC use. The problem is that the shanks are also 10mm. I have one in 8mm, and have an 8mm-to-1/2" adapter. Is there such an adapter for 10mm-to-1/2"?

Regards from Perth

Derek

[John Kananis]

Is this what you're looking for? You mean a collet adapter I believe.

https://www.whitesiderouterbits.com/search?q=6400x10

[John TenEyck]

Just use a 1/2" bit. 10 mm vs 12.5 mm; there is no meaningful difference. Why make things difficult/expensive?

John

[Kevin Jenness]

I agree with John. You have a 1/2" d. bit long enough for your liking, it will leave sufficiently strong sidewalls, so why not use it? Starting a mortise into endgrain with a Domino 500 and deepening it with a drill and chisel would be difficult and not improve the result significantly if at all over a well-fitted 1" deep mortise made only with the Domino. I would be wary of using a bit longer than 4x diameter in a hand-held router.

[Greg Quenneville]

I might have some 3/8” endmills Derek. I can send one to you if you are going to get a collet sleeve.

Greg

[Derek Cohen]

Thanks for the offer Greg. Much appreciated. However, I think that it makes sense to use the 1/2" spiral upcut (CMT carbide).

https://i.postimg.cc/CKyS4LTT/6.jpg

This has around 3" depth of cut (100mm/4" length).

So, instead of walls 10mm thick, they will end up roughly 9mm thick.

Regards from Perth

Derek

[Jim Becker]

Jim, thanks. I have been searching for a 10mm spiral bit. The ones I find are end mill bits for CNC use. The problem is that the shanks are also 10mm. I have one in 8mm, and have an 8mm-to-1/2" adapter. Is there such an adapter for 10mm-to-1/2"?

Regards from Perth

Derek

You should be able to find a .375" to .5" collet reducer "out there". Some routers do have available collets I suspect, but it's a less common size for these tools. I'm a little spoiled in that respect given the wonderful ER collet systems used with spindles in CNC context.


BTW, the tool I mentioned is a "Cobra" brand and available on Amazon. Not sure what your buying options are for tooling, but I cannot imagine that you cannot find the same or similar somewhere in your buying options. You might even be able to source a .375"/10mm tool with a .5" or 12mm shank

[Warren Lake]

You better use extra care if you run the 4 inch 3 inch cutting capacity bit. They are meant to be in machines and in a router there can be vibration and whip. I used mostly 2 inch cutting capacity but also the three inch as well. They were high speed steel end mills for milling machines. Cut very well but I went through tons of them changing them out as soon as they were getting dull. Long bits like that can get whip in them and vibration.

On one occasion I had the 4" bit in and router running turned it in front of me to lay it flat on a carpet on the bench. I cant remember if I switched it off as i had other jobs where the routers were left on all the time. As I turned the router to lay it down did the wind from the router sucked up my Red Green shirt which was not tucked in and shirt wrapped around the bit pulled the router right into my stomach bit first. I was not hurt, the shirt stalled the router.

[Keegan Shields]

Yikes! I would need some new underwear after that Warren.

[John Kananis]

Yikes! I would need some new underwear after that Warren.

Agreed. That sounds terrifying.

[Warren Lake]

its was fine as I was not hurt. I dont mind an incident if im not hurt, or even the ones where I was hurt some amount but not enough it mattered. It was fairly un expected though with so many years on routers. Should have kept the shirt and put it on a hanger in the shop. Id call it a good day as a lesson was learned, id always been careful with loose clothing, sleeves, not wearing gloves etc. A reality of those really long bits is that on a plunge router it may not retract far enough so the bit is always projecting. Now you have to pay attention to your jig thickness and set up. In my case I was cutting from the side of the bit so it was left locked in the one position.

[Derek Cohen]

Warren, when it comes to using a router for morticing, this is the fixture I made several years ago. It allows the router to run along a track (deep wooden groove) without tipping. The work piece is clamped below …


https://www.woodcentral.com/home/uploads/2022/11/861_20221108.jpeg


https://www.woodcentral.com/home/uploads/2022/11/355_20221108.jpeg


https://i.postimg.cc/qvdd6H7M/87426017-CD42-4-ECA-AE75-A00-F14-CF3410.png
My hesitation in using this at the start was that I preferred to use a 10mm bit, which I do not have. Now I believe that I have been over-estimating the stress on a head- and tail end. The racking issues lie with the sides, not the ends. I plan to review the use of bed bolts there, but the head/tail loose tenons could be 10mm or 12mm and this will be strong enough.


Regards from Perth
Derek

[Warren Lake]

Derek your jigs are nicer than my furniture. I didnt do much plunge mortise stuff as I have a mortise machine. I doubt you could use the 4" bit in your router on that set up, maybe if so that router would have alot of travel. I guess a hole could be drilled as well to start the router if the bit extended too far. Past I was using a makita for lots of that work then got porter cables. I didnt read from the start but see you are mortising from the end in which case yeah the bit can be hanging out.

[Tom Bain]

Not sure if it’s an issue here, but I have used a shorter 1/2” spiral bit to start a deep mortise and then switched over to a longer bit once the mortise was deep enough to accommodate it. A little bit of pucker factor when you start up the router with the bit already in the mortise, but it worked!