Hidden bed bolts

[Derek Cohen]

The two beds are nearing completion of the joinery. The last report was making loose tenon using the Domino DF500 to create the mortices.


The rails are 125mm x 26mm. The mortice is 115mm x 10mm ...
https://www.woodcentral.com/home/uploads/2022/11/340_20221127.png


These are the bed ends. It is relevant to note, as the tenons extend just 28mm into the end rails, they are not in danger of coming apart from the posts. The stresses (racking) will be on the side rails. In any event, the tenons will also be pinned.


https://i.postimg.cc/fLRfMckh/15.jpg


The challenge now is to hide the bed bolts which will connect the side rails. Generally, the bolts run through the post and terminate in the side rail. My aim was to retain the clean, uncluttered line of the tapered posts. There are mechanical fasteners available, but I have used these in the past and the lighter, single beds are vulnerable to racking in my experience.


The end result needed to look like this ...
https://i.postimg.cc/T19qVj9k/28.jpg

I began by adding double 40mm x 10mm wide x 12mm deep mortices in the posts ...
https://i.postimg.cc/sXbtFzCF/32.jpg


These were initially made with the Domino, and then the ends squared with a chisel. Why squared? Because I find it easier to fit tenons exactly when they are squared than when they are rounded.


The tenons were planned to be 10mm x 10 mm. These were made with a router and a simple fence ...


https://i.postimg.cc/N0jhmbkn/29.jpg

The fence is positioned by a depth stop (top left).


https://i.postimg.cc/sXMt0X89/30.jpg


... flipped, set up, and routed again ...


https://i.postimg.cc/MGPCDRsp/31.jpg


Saw and chisel to a matching fit ...


https://i.postimg.cc/d3dgwfJh/33.jpg


The ground work is set for the bed bolt. Insert a dowel centre between the tenons ...


https://i.postimg.cc/TYVBsBkS/36.jpg


Insert the tenon end into the mortice end, and this will mark to position where the bolt will go ...
https://i.postimg.cc/13yb1M2z/37.jpg


Drill and insert a steel thread (wet the wood to make tapping easier) ...


https://i.postimg.cc/cLT2xwGB/38.jpg


I am using a M8 stainless steel bolt (cut the head off) ..


https://i.postimg.cc/Gp2NHtcw/39.jpg


A short pilot hole is drilled, using a Stanley #59 dowel guide ..


https://i.postimg.cc/wBGrJzvt/40.jpg


This is extended with a long 6mm drill bit, taking care to aim for a slight angle towards to inside face. The reason for the slight angle is to reduce the depth for the bolt. The bolt hole is widened to 9mm.


The bed bolt extends to the centre of these two forstner-made holes.
https://i.postimg.cc/W3qHwyF5/41.jpg

[Derek Cohen]

Smaller holes are added for a spanner, and the end is squared for a washer and nut.

https://i.postimg.cc/NFhPJxRB/42.jpg

https://i.postimg.cc/gjvtf6KR/43.jpg


Time to begin adding finish and glueing up the end rails.

Regards from Perth
Derek

[John TenEyck]

Always nice clean work, Derek. You might consider using Zipbolts for that application in the future. Much easier to tighten/loosen.

John

[Derek Cohen]

Thanks John. The Zipbolts look strong but a little more bulky than desired. There was nothing special about the hardware I have used, but it does the same thing. Agreed, probably more more though.

Regards from Perth

Derek

[John TenEyck]

There are different size Zipbolts. You could still use the insert in the leg, as you did. The business end is no larger than the area you excavated in the rail, likely less. I made a little template to route the recesses. You can glue a strip of wood into the dado section that you have to cut to install the Zipbolt, if you want to minimize the amount of wood removed. Just a suggestion.

I look forward to the rest of your build.

John

[andy bessette]

Just a suggestion:
A piece of round bar stock (say 1-1/2" diameter steel or aluminum) could be cutoff and tapped, crosswise, through its center to create a threaded insert That way the mortice for its installation could be achieved by means of a simple round counterbore in the bed frame. And the metal insert would neatly fill the counterbore.

https://i.postimg.cc/fLrGfsMt/IMG-1607.jpg (https://postimg.cc/G8vgbZ8d)

[Derek Cohen]

Andy, thanks. I am aware of these fittings. All the counterbore set ups I am familiar with are required to be drilled where they are visible, or interfere with the mortice-and-tenon from the end rails. Thoughts?

Regards from Perth

Derek

[andy bessette]

Andy, thanks. I am aware of these fittings. All the counterbore set ups I am familiar with are required to be drilled where they are visible, or interfere with the mortice-and-tenon from the end rails. Thoughts?

Regards from Perth

Derek

The single counterbore I refer to can replace the series of counterbores in your photo. No need to be visible or interfere with the tenons. Would provide a more finished appearance.

[Derek Cohen]

Do you have a photo, Andy?

Regards from Perth

Derek

[Kevin Jenness]

Just a suggestion:
A piece of round bar stock (say 1-1/2" diameter steel or aluminum) could be cutoff and tapped, crosswise, through its center to create a threaded insert That way the mortice for its installation could be achieved by means of a simple round counterbore in the bed frame. And the metal insert would neatly fill the counterbore.

https://i.postimg.cc/fLrGfsMt/IMG-1607.jpg (https://postimg.cc/G8vgbZ8d)

Those cross dowels are commonly used with through bolts. https://www.rockler.com/heavy-duty-cross-dowel-and-bolt-8-pack It's not clear to me how you would use them in Derek's blind fastening situation.

I have never liked those threaded inserts due to the difficulty of threading them into hard wood and winding up with the bore square to the surface. In this case I would consider modifying the end frame joinery from one wide to two narrower ones leaving material to pot the bolts in epoxy. The thread engagement could then be nearly the full depth of the post.

[Derek Cohen]

Thanks Kevin. If your link is the one, then it would not be applicable in my situation as it could not be used blind. It is designed to be used through the post, exiting at the front - which is what I am avoiding.

Regarding threading inserts into hardwood, I mentioned wetting the wood inside the drilled hole before threading. This softens the end grain enough. Jarrah has a tenacious grip! Those inserts are not coming out. The threaded bolt is then attached with Loctite 222. This is enough to hold the bolt, but can be broken by twisting the bolt.

Regards from Perth

Derek

[Edward Weber]

If I can suggest, I would use a half moon washer in the mortise. Les work mortising and the pressure is spread out over a larger contact area.

[Derek Cohen]

Edward, these washers are not available locally. They do look good, and I would have used them if it was possible, but I used what I could find. There were 8 ends to build. It is not like I was going into production. A few chops with a chisel, and done. This is all hidden on the inside of the bed, and under the rails for the cross pieces.

Regards from Perth

Derek

[andy bessette]

Do you have a photo, Andy?...

It is a concept. Best I can do is a photo of my sketch.

Along the axis of your bolt hole you counterbore for the "insert". The "insert" is a piece of round metal bar stock through which you cross-drill and tap the appropriately sized thread to match your bolt. The "insert" fills the counterbore completely and provides the threads into which the bolt is screwed.

https://i.postimg.cc/L5pHGWC8/IMG-1608.jpg (https://postimg.cc/LYxK1xFc)

[Derek Cohen]

Andy, I assume that the bolt enters between the tenons and is seated in the round thingamajig? Where is the other end of the bolt, and how does one tighten it? Presumably on the other side of the post? In other words, not hidden?

Regards from Perth

Derek

[andy bessette]

...Where is the other end of the bolt, and how does one tighten it? Presumably on the other side of the post? In other words, not hidden?...

Under a wooden plug in a counterbored hole in the mating part.

[Edward Weber]

Edward, these washers are not available locally. They do look good, and I would have used them if it was possible, but I used what I could find. There were 8 ends to build. It is not like I was going into production. A few chops with a chisel, and done. This is all hidden on the inside of the bed, and under the rails for the cross pieces.

Regards from Perth

Derek

If the bed does rack, and it will, you may have issues down the road.
In your application, the M&T joint is mainly for alignment, the strength of the connection is from the threaded connection, you need to make it as strong as possible. IMO M8 is too small/weak for a side rail/end connection, but that's just me. This joint takes quite a lot of force.
This contact point it very small in proportion to the width of the joint. All of the force from racking will be focused on that one point. What usually happens is that the nut starts to bury itself into the side rail, with a potential to split and/or bend the threaded rod.

This is why half moon washers are used, and the shaft hole is usually slightly oversized.

[Mel Fulks]

The traditional bed bolts work well. Many of the covers look better than most ladies jewelry. Most tall post fine beds of today don’t have
any hangings and that greatly reduces the beauty. Before screened windows or air conditioning the tall post beds had “mosquito netting “.
We have a friend who found an old bed with hangings , and it is spectacular! Besides the netting, it has curtains that slide open. People who
had such beds usually had servants, so they needed privacy.
I forgot the warmth of the hangings ….and the sound proofing !

[Derek Cohen]

If the bed does rack, and it will, you may have issues down the road.
In your application, the M&T joint is mainly for alignment, the strength of the connection is from the threaded connection, you need to make it as strong as possible. IMO M8 is too small/weak for a side rail/end connection, but that's just me. ....

This is why half moon washers are used, and the shaft hole is usually slightly oversized.


Bed bolts come in M6 (6mm) or M8 (8mm). The equivalent Imperial is 1/4" and 3/8". I have used the larger size.

The shaft hole used is 9mm.

The reason, as I see it, for the half moon washer is to use a flat bolt surface against a curved edge (created by a hole). The flat I chiseled is as strong, keeping in mind the wood is Jarrah (very hard). I did consider a large, single hole for the bolt end, but that would have removed more wood. I was trying to minimise what was removed.

Regards from Perth

Derek

[Malcolm McLeod]

The wood under the nut/washer may compress a bit, but that can be addressed by simply tightening the nut.

The weak spot is the threaded insert. It will fail over time due to the racking forces and significant leverage advantage of the legs. Bed bolts traditionally pass through the leg for some hard won ‘engineering’ reasons.

What is the size of the insert thread engaged to the leg? 12mm? …15mm? If you are thinking it will hold, then you could replace the 8mm threaded rod with a 12 or 15mm hanger bolt and get the same result. I would hazard a guess that no one would do this for two reasons: there is virtually no way to repair a failure of the wood thread; and perhaps too obviously folks think it will fail.

JMHO. (And the wood working is your typical top-notch.)

[Edward Weber]

Bed bolts come in M6 (6mm) or M8 (8mm). The equivalent Imperial is 1/4" and 3/8". I have used the larger size.

The shaft hole used is 9mm.

The reason, as I see it, for the half moon washer is to use a flat bolt surface against a curved edge (created by a hole). The flat I chiseled is as strong, keeping in mind the wood is Jarrah (very hard). I did consider a large, single hole for the bolt end, but that would have removed more wood. I was trying to minimise what was removed.

Regards from Perth

Derek


I believe Malcolm summed it up pretty well.

The solution would be to use a central tenon and two bolts per connection, flanking the M&T joint. A single bolted connection creates a pivot point for racking. It's obviously too late for this project, but something to keep in mind.

"Bed bolts come in M6 (6mm) or M8 (8mm). The equivalent Imperial is 1/4" and 3/8". I have used the larger size"

The equivalent Imperial is 1/4" and 5/16".
A 3/8" bolt, like many older style beds use, would be 9.5mm.

One thing to keep in mind is that when you're using a dense, hard species like Jarrah, there isn't any "give". This means, any flex or movement will be in the connections, i.e., the hardware. The hardware must be as strong as the wood, so as not to create a weak link in the chain.

Hope it works out for you

[Mel Fulks]

Under a wooden plug in a counterbored hole in the mating part.

yes, and they go back to at least early 19th century. I bought a child’s crib made in a shop that was out of business by 1820.

[Derek Cohen]

I believe Malcolm summed it up pretty well.

The solution would be to use a central tenon and two bolts per connection, flanking the M&T joint. A single bolted connection creates a pivot point for racking. It's obviously too late for this project, but something to keep in mind.

"Bed bolts come in M6 (6mm) or M8 (8mm). The equivalent Imperial is 1/4" and 3/8". I have used the larger size"

The equivalent Imperial is 1/4" and 5/16".
A 3/8" bolt, like many older style beds use, would be 9.5mm.

One thing to keep in mind is that when you're using a dense, hard species like Jarrah, there isn't any "give". This means, any flex or movement will be in the connections, i.e., the hardware. The hardware must be as strong as the wood, so as not to create a weak link in the chain.

Hope it works out for you

What is still possible is to add a narrow mortice in the post behind the threaded insert and drop in a threaded steel plate.

https://i.postimg.cc/gjvtf6KR/43.jpg


I made these for my bench many years ago ...

http://www.inthewoodshop.com/ShopMadeTools/BuildingaBench5_html_1eda0a2f.jpg


I should add that my expectation/understanding of racking is that it would be minimal anyway. The joint is not simply via a bolt. There are two shallow but tight fitting mortice and tenon joints. These alone lock the post and rail together without any vertical movement. The bolt is to keep them together. Your thoughts?

Regards from Perth

Derek

[Edward Weber]

Your expectation of racking is that it will be minimal, what often happens in the real world can be different.
If the M&T is a tight fit, this will help keep the joint from experiencing any unnecessary movement but not eliminate it totally
How these beds are used and by whom has a direct effect on the longevity of the joints remaining tight.

If someone gently sits on a bed, there is little racking force applied. If I flop down on the bed after a long day, my 200+ lbs will have more of an effect. If children are jumping up and down, etc.
Beds take a lot of abuse and must be made as strong as possible. This is why hook plates are often used as an invisible fastening system. Their design keeps them tight when weight is on the bed frame.

The main point is to make them as sturdy as possible, even beyond what you think is heavy duty. Just google wobbly bed frame and see the results.

[Malcolm McLeod]

….
I should add that my expectation/understanding of racking is that it would be minimal anyway. The joint is not simply via a bolt. There are two shallow but tight fitting mortice and tenon joints. These alone lock the post and rail together without any vertical movement. The bolt is to keep them together. Your thoughts?

Regards from Perth

Derek

“Minimal” can mean a lot of things, and racking (perceived motion) vs applied force are different.

Humans activity, whether pushing it closer to the wall, or uhm… interacting, with the bed frame, will cause racking and apply a force in the long axis of the bed frame. I haven’t tried to scale your photos, or read back for dimensions, but a quick and dirty stab at a static torque diagram would lead me to believe you have built a lever with somewhere between 4:1 to 5:1 advantage. White-board calc, with typical bed dimensions, says a 5lb belly flop would pull on the insert with ~23lbs; 200lb dive pulls on it with 920lbs (417kg), not counting inertia. …my thoughts. Hope it helps.

(ETA - Reality says such a load would be shared by all 4 joints. I have assumed 1 joint carries it all as a safety factor. I tend to over-build.)

[Edward Weber]

“Minimal” can mean a lot of things, and racking (perceived motion) vs applied force are different.

Humans activity, whether pushing it closer to the wall, or uhm… interacting, with the bed frame, will cause racking and apply a force in the long axis of the bed frame. I haven’t tried to scale your photos, or read back for dimensions, but a quick and dirty stab at a static torque diagram would lead me to believe you have built a lever with somewhere between 4:1 to 5:1 advantage. White-board calc, with typical bed dimensions, says a 5lb belly flop would pull on the insert with ~23lbs; 200lb dive pulls on it with 920lbs (417kg), not counting inertia. …my thoughts. Hope it helps.

(ETA - Reality says such a load would be shared by all 4 joints. I have assumed 1 joint carries it all as a safety factor. I tend to over-build.)




Malcolm, that's what I was trying to say, just not as technically, thanks

Not trying to beat up on Derek, but many people don't understand the forces these joints are subject to.
A bed rail is essentially a 6" lever attached to your joint.

[Derek Cohen]

Edward, I am always ready to learn more, in this case about the stresses in bed ends. These would only be the 4th and 5th I have done, and the first with bed bolts.

It strikes me that there are two ways to beef up the existing bolt. The first is the plate I described above. This simply adds strength to the existing bolt, but does nil for racking. The second is to add small angle plates in the corners above- and below the bolt. That would resist any racking.

Regards from Perth

Derek

[Kevin Jenness]

No doubt the joint would be stronger with two bolts, but one would search far and wide before finding a picture of a traditional bed frame with more than one bolt through the posts.

If you are concerned about the threaded insert pulling out and have the depth to drive it deeper, then a larger cover plate let into the post would beef it up. I don't think you need be worried about using a single bolt, especially on a single bed that will see less action than one with more occupants.

[Mel Fulks]

Agree with Kevin. The bolts replaced the “rope beds “ ,and that was a giant leap forward. Some people wanted the Empire State Building
“stronger” but good engineering worked okay.

[Edward Weber]

OP's bolt is a single 8mm (5/16") bolt, a larger 9.5mm (3/8") bolt is about 30% larger which adds strength.
Two 8mm bolts would be even stronger and would have somewhat more resistance to racking, as there is no single pivot point, depending on how far apart they are spaced.

Most beds bolted with a single bolt (3/8"-9.5mm) are through the posts, not threaded into an insert. This, along with their larger shaft, allows them to be tightened more and withstand more forces that act upon them.

[Derek Cohen]

I did research the bolt sizes earlier on. Most came in at 8mm. Some were 6mm.

Example of those similar to the set up I am using:

https://www.thefrenchbedcompany.co.uk/antique-french-bed-replacement-bed-bolts-thread-fixings-pk-4-uk-post/

https://zipboltonline.com.au/cabinet-hardware/bed-connectros/zipbolt-ut-mini-12-700-kd8-8mm-x-90mm.html

https://www.fishpond.com.au/Homeware/Concealed-M8-bed-boltsHalf-MoonCrescent-washersREPLACEMENTNO-INSERT-NUTS-lengths-75mm-200mm/9999098001649

This was an article which I consulted along the way. Not an insert connection, but again 8mm/5/16” bolt …
https://www.scottjordan.com/information/assembling-queen-size-bed


A corner block is another way of avoiding any possible wracking:

https://i.postimg.cc/HdyS3GmH/4-BB36023-4594-4213-85-F9-8-DB295369-D2-C.jpg
https://sawmillcreek.org/blob:https://sawmillcreek.org/92167f43-5767-4d4f-9371-8bd048eb4f98

I am tempted at present to just let the build proceed as is, and deal with any issues if they arise in the future.

Regards from Perth

Derek

[andy bessette]

...I am tempted at present to just let the build proceed as is, and deal with any issues if they arise in the future...

Of course. The comments were simply open discussion, not a recommendation for redoing the work.

[Mel Fulks]

Absolutely, Derek ! You have turned out a lot of good work , and will turn out a lot more ! I doubt their will be any “issues”. Yes , people
of the future might say “ this is a fine beautiful bed ,but just looking at those weird connectors I’m thinking he must have lived on an
isolated island…”

[Derek Cohen]

Thanks Mel. To be safe - now that some doubts have been created - I have ordered steel corner braces for insurance. These are designed for tables, but should fit. While waiting, the beds are now closing in on the final stage. I will post pictures once done.

Regards from Perth

Derek

[Malcolm McLeod]

If the corner braces correspond to the corner block in the #31 post, they will resist 'racking' in the horizontal plane (x-y). The bed slats, deck, and/or mattress should generally resist this without need for such a brace.

My references to loads and insert pull out are based on a vertical plane (x-z).

[Mike Allen1010]

Derek, the bed frames look beautiful. I’m eager to see the finished product. I’ve built three different beds, I think your construction looks great. “If it’s not broke, don’t fix it“. Thanks for posting.

Best, Mike.