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By Trevanion
#1305193
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.
By Woody2Shoes
#1305200
Wurm wrote: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
By Wurm
#1305234
Woody2Shoes wrote:
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".
By profchris
#1305251
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.
By Woody2Shoes
#1305260
Wurm wrote:
Woody2Shoes wrote:
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
By rafezetter
#1305439
Wurm wrote: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.


Right idea but wrong bit - the simplest way would be to make a block that's glues to the side of the door rail at the point the top (or bottom) face of the clamp meets that point.

If you read my last paragraph in my above post and do what I suggest, that will give you an idea of what you are needing.

Apart from the issue of making a glue block that will sit "nicely" on the arch, which would involve making it match the curvature of the arch (more work), I can't envision any way that this would help your situation because the geometry is all wrong.

Soft wood or hard for the block is irrelevant as there'll be no "ripping" of anything :shock: - if you use wood glue as many people do, you'll PLANE it off down to the level of the door rail, a little sanding and it's done - if you have a hot glue gun then you can either soften it with a heat gun (can get a bit messy) or make it cold and brittle with one of those air cannisters used upside down so it sprays the propellent in the can which will come out very cold.

I've seen Norm Abrams use the paper trick and put copy paper in the glue joint to reduce it's effectiveness - essentially apply glue on both faces to be glued, and slip a bit of paper onto the glue on one of the faces, then apply the item you are gluing. I've seen it's a firm enough bond to do what's needed but then he's able to break apart that glue joint with his hands, leaving some easy cleanup.
By rafezetter
#1305445
Trevanion wrote: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.



Ahh have to agree with Trevanion - even though I'm by no means an expert I beleive it's pretty much a cardinal rule with this sort of thing (splines etc) that the grain of the loose tenon be perpendicular to the joint.

What you have now is sympathetic grain running parallel with the joint - which makes it a lot weaker and if the loose tenon seasonally expands inside the joint, which it will do parallel to the grain, the joint will have no option but to "pop" as Trevanion says.

Pegging /drawboring / dowelling won't fix this and will actually guarentee a bad result.

The block needs to be re-made - and this is pretty imperative you do it - and done so with the grain running the opposite way. However if you made it square, just turn it 90deg :) Actually on reflection if it's not square, gluing a thin shim of wood to the side to make up the difference is just as good.
By rafezetter
#1305447
Woody2Shoes wrote: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 said that :) )
By dzj
#1305504
rafezetter wrote:What you have now is sympathetic grain running parallel with the joint - which makes it a lot weaker and if the loose tenon seasonally expands inside the joint, which it will do parallel to the grain, the joint will have no option but to "pop" as Trevanion says.

Pegging /drawboring / dowelling won't fix this and will actually guarentee a bad result.

The block needs to be re-made - and this is pretty imperative you do it - and done so with the grain running the opposite way. However if you made it square, just turn it 90deg :) Actually on reflection if it's not square, gluing a thin shim of wood to the side to make up the difference is just as good.


+1 regarding the grain direction, but even if he turned it 90 deg, it'll still be short.

If I understand correctly, the door would be boarded on the outside. In such cases a halflap joint, glued and secured with screws (hidden under the boarding) would be enough for a door this size.
By Woody2Shoes
#1305607
rafezetter wrote:
Woody2Shoes wrote: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 said that :) )


(... yebbutt after I did (and I found a good video of it) :lol: :wink: ...)
By Wurm
#1305608
Can anyone recommend a method for cutting a mortice right through the arch? My router has an 'edge band' attachment which might allow me to run a straight cutting bit perpendicular to the face of the arch, but there must surely be a standard method.
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By AndyT
#1305642
Wurm wrote:Can anyone recommend a method for cutting a mortice right through the arch? My router has an 'edge band' attachment which might allow me to run a straight cutting bit perpendicular to the face of the arch, but there must surely be a standard method.


Sorry this is another "you can't get there from here" answer, but for most curved work the standard method is to cut the joints first, on square timber, then cut the curves.
Seeing as how that's not very helpful for you, you could try adding a shaped piece onto the curve so it's square again, cutting the joint, then removing the extra bit. Somewhat like the temporary blocks to angle the sash cramps.
By owen
#1305688
Wurm wrote:Can anyone recommend a method for cutting a mortice right through the arch? My router has an 'edge band' attachment which might allow me to run a straight cutting bit perpendicular to the face of the arch, but there must surely be a standard method.


Hand saw and chisel? From above? By edge band attachment I think you mean a fence?
By Wurm
#1321120
Can anyone recommend a workstand designed to clamp a piece of wood such as this in a vertical orientation? I have figured out (I think) how to cut the mortice so I just need to hold it in place while I work on the end.

I could clamp it to the banister but I would rather keep the dust out of the upstairs hall.
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By AndyT
#1321122
A proper (ie old) B&D Workmate could work, if there is enough space.

Or possibly a big piece of wood on each side (such as a joist offcut or scaffold plank) clamped onto the work, arranged to butt up against the opposite wall.

These are just guesses and might work in your space, or not!