Clamping an arch

[Wurm]

This is the top section of a stable door that I have cut and is ready to glue together. I am guessing it should be clamped from one arch to the opposing corner unless anybody tells me otherwise.

It is only the second item that I have made out of wood, the first having been an airing cupboard, so any thoughts on how best to bond it will be appreciated.

 

[MikeG.]

With such a pronounced arch I would start with a ratchet strap around the whole thing, with suitable corner protection. I'd also be using sash cramps........carefully.

 

[rafezetter]

Have to say pretty impressed if that really is only the second thing you've made from wood - you've definitely got a talent for it.

Seems MikeG beat me to it.

I'm assuming you've got something inside those butt joints for the middle and ends of the arch; like a biscuit or domino or... something?

 

[marcros]

It depends what clamps you have. I think that I would use glue blocks, because I hate ratchet straps with a passion.

 

[AndyT]

I too am impressed that a beginner has managed something so ambitious. Although I have never needed to make such a door, if I did, I'd want to follow the traditional construction and use hammer head tenons. Although it looks complicated, this method has the big advantage that the joints are tightened up by wedges, meaning that complicated clamps on the arched part are not needed.

https://en.wikipedia.org/wiki/Hammer-headed_tenon

 

[Argus]

Here's an example of a hammer-head joint.
It is a door at Plas-Glyn-Y-Weddw in North Wales.

 

[Adam9453]

Based on where you’re upto I’d just glue some temporary blocks on so you can use a sash cramp to pull it tight without any issues, just be careful when you remove them

 

[ColeyS1]

Based on where you’re upto I’d just glue some temporary blocks on so you can use a sash cramp to pull it tight without any issues, just be careful when you remove them

Sound advice!


Sent from my SM-G960F using Tapatalk

 

[Wurm]

I bought some of these clamps for the job:

https://www.bahco.com/en/p/plastic-hand ... -d9-9b-3b/

The arch is connected with a double mortice at each end and a block of wood to connect them (I think that is a biscuit?). I should have asked on here for advice before now since none of the books I read mentioned a hammerhead joint.

Ratchet straps I am familiar with, but when I did an online search for 'glue block' every return talked about something for wood turning, so I am not quite sure how that would work.

Two more questions:

I have procured an old glass table top as a flat surface to glue it on, should I put down some wax paper or equivalent so the door does not get stuck to the glass? Should I also use it around the joints if I use a ratchet strap?

One of the tenons in the base is too narrow for the mortice (I made a mistake on the cut), would mixing some sawdust and chippings with the glue help to fill the gap?

Your time to reply is appreciated.

 

[Racers]

Glue a shim to the loose tenon and pair it to fit, we have all done it.

Pete

 

[dzj]

The arch is connected with a double mortice at each end and a block of wood to connect them (I think that is a biscuit?). .

If you're using biscuits, I think you should consider using some other joinery method.
I'll assume that you're using floating/ loose tenons. You could go without clamps completely and glue one side and when it dries, drawbore and glue the other.

 

[TheTiddles]

If you can stick to glass with wood glue, you deserve a prize! However thin plastic is my go to, old plastic bags, bin bags, cling film etc...

As for the gappy tenon, if the gap’s more than a small fraction of a millimetre, use a thin bit of wood like veneer, it’ll also match better if it’s visible

A

 

[Trevanion]

I should have asked on here for advice before now since none of the books I read mentioned a hammerhead joint.

What books are you reading out of curiosity? There seems to be some interesting joinery going on with your door I haven't really seen anywhere else.

 

[rafezetter]

Wurm - for the glue blocks what they mean is something like this:

https://www.pinterest.co.uk/pin/176766354098993858/

There are two common types - reusable removable ones that are clamped to the work first then the angled clamp applied after, usually for repeated work.

The second is little more than a wedge that has been cut to a corresponding angle from the other angled face you wish to clamp and then glued onto the workpeice for clamping - once the clamping has been done and the glue dry - it's then cut and planed off.

In your case you take a sliding bevel and take a reading setting the body of the bevel so its sitting on the end of the arch mitre joint and angle the bevel part to match the average of the arch angle.

Then you get a bit of scrap large enough for your clamp head and cut it to that angle, and then glue it to the side of the door frame roughly in the middle - ensuring that the angled face you don't glue is the correct one and should be approximately parallel to the arch curve - also making sure it's not so low the clamp face can't reach it - you want to try to get the clamp face as close to the middle of the stock on both peices as possible or uneven pressure could lead to the inside glue joint being tight and the outside having a gap.

I'm not explaining it so well.... this might help you get the gist:

https://www.google.com/search?rlz=1C1AS ... APmd-2iA08

It is pretty straightforward... but remarkably complex to explain without a good reference !

Basically you're trying to make a block so that when the face of the clamp sits flat on the arch - it has a corresponding bit of wood on the side of the door stile opposite that matches the angle of the clamp face as it is presented.

Grab a clamp and put the bottom face roughly in the middle of the arch, then look at the top head and the angle of the clamp face in relation to the side of door stile - that's the angle you want to replicate in a block of scrap wood.

err hope that helps?

 

[Wurm]

This is the connection between the two sides at top of the arch, the other connections are similar. If the double tenon, if that is the right term, is not big enough I could still cut something longer.

If I am understanding it right, a glue block is made a of a soft wood and glued onto the arch so as to provide a clamp point, and then when it is removed the soft wood should rip apart leaving the oak intact. I have some thinking to do there.

 

[Trevanion]

I don't want to be a naysayer but I don't think that connection is going to be strong enough to hold against seasonal changes and wood movement. It's a very small tenon with minimal long-grain glue faces, the whole joint is going to be practically relying on an end-grain glue joint which with the instability of oak and the changing seasons the joint will just "pop" and get worse, and worse.

 

[Woody2Shoes]

This is the connection between the two sides at top of the arch, the other connections are similar. If the double tenon, if that is the right term, is not big enough I could still cut something longer.

If I am understanding it right, a glue block is made a of a soft wood and glued onto the arch so as to provide a clamp point, and then when it is removed the soft wood should rip apart leaving the oak intact. I have some thinking to do there.

Here's Mr. Vondriska doing the woodblock clamping trick: https://www.youtube.com/watch?v=AFUrpRTI6q0 It's not so much the softness of the block as the weakness of the (hot melt in this case, but sometimes people use PVA with a sheet of paper in between) temporary glue joint.

I might have been tempted to join the curved sections with splines/loose-tenons - to ensure a good level of longgrain-longgrain contact in each glue joint - a little bit like this: http://2.bp.blogspot.com/-c0CMaHSkLU4/T ... G_2938.JPG

Cheers, W2S

 

[Wurm]

Here's Mr. Vondriska doing the woodblock clamping trick: https://www.youtube.com/watch?v=AFUrpRTI6q0 It's not so much the softness of the block as the weakness of the (hot melt in this case, but sometimes people use PVA with a sheet of paper in between) temporary glue joint.

I might have been tempted to join the curved sections with splines/loose-tenons - to ensure a good level of longgrain-longgrain contact in each glue joint - a little bit like this: http://2.bp.blogspot.com/-c0CMaHSkLU4/T ... G_2938.JPG

Cheers, W2S

I am not following that bit. When you refer to 'hot melt', does the glue come apart with a heat gun before the oak starts to char? By putting a piece of paper between the two pieces of wood does that reduce the damage to the oak?

What size floating tenon do you recommend? The arch is 4" X 2".

 

[profchris]

I don't have much experience with glue blocks, but some (from musical instrument making) removing wood glued to other wood without damaging one of the pieces.

The easy way, if you use Titebond Original or PVA, is to chisel and plane away the block until only a paper-thin sliver is left. Then if you damp a few thicknesses of paper towel and apply a medium iron on the wool setting until the steaming stops, the sliver of your block should just peel off. A warm damp cloth, or sanding when dry, will remove glue residue.

This is the safe way to remove guitar bridges if a new bridge is being made.

 

[Woody2Shoes]

Here's Mr. Vondriska doing the woodblock clamping trick: https://www.youtube.com/watch?v=AFUrpRTI6q0 It's not so much the softness of the block as the weakness of the (hot melt in this case, but sometimes people use PVA with a sheet of paper in between) temporary glue joint.

I might have been tempted to join the curved sections with splines/loose-tenons - to ensure a good level of longgrain-longgrain contact in each glue joint - a little bit like this: http://2.bp.blogspot.com/-c0CMaHSkLU4/T ... G_2938.JPG

Cheers, W2S

I am not following that bit. When you refer to 'hot melt', does the glue come apart with a heat gun before the oak starts to char? By putting a piece of paper between the two pieces of wood does that reduce the damage to the oak?

What size floating tenon do you recommend? The arch is 4" X 2".

If you watch the video you'll see he's using hot melt glue to attach the temporary blocks (or 'blacks' as he seems to call them!) - the hot melt glue is relatively weak - just strong enough to hold the clamping pressure. He then uses a short mallet blow to break the joint - I guess he could have used a heat gun to undo the joint, but he might have damaged the workpiece (charring the wood or pinging the glass) as you suggest.

Regarding the piece of paper, it's simply to weaken the glue joint between the workpiece and the temporary block - a trick that woodturners often use. Here's George V. again, demonstrating that alternative technique: https://www.youtube.com/watch?v=vJNCRhVJe8U

Also https://www.youtube.com/watch?v=yhV2UyqB94c

PS I'd use splines about 15mm X 75mm X 125mm - with an exterior grade glue - I suppose you could still do things that way without wasting much of the (very tidy looking) work you've already done