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Laminating a curve - with a twist.

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Laminating a curve - with a twist.

Postby 9fingers » 23 Jan 2019, 18:02

I had a job turn up for which I needed two 20 mm square lengths of oak with a curve at one end.

Like this lower component

Skids -photos 015.jpg
(270.95 KiB)


I decided to do it by lamination as I had no facilities for steaming but it seemed a waste to make the whole piece from laminations as most of it would be straight so I chose to make it using kerf cuts and matching infill pieces glued in.

I used a fine kerf blade (2mm approx) designed for a portable saw and ore out the hole from 5/8" to 30 mm to fit the tablesaw.

Skids -photos 024.jpg
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The ends of the kerf cuts are curved naturally to the cirumference of the blade. Putting a protractor into the cut I estimated the angle of a line to form the chord of the end of the cut and trimmed the infill strips to that angle.

Angled end of the infill strips

Skids -photos 021.jpg
(235.53 KiB)


The strips were cut from anothe piece of the same oak and thickness sanded to a sliding fit in the kerf allowing for a layer of glue.

Dry fitting in the strips looked like this

Skids -photos 023.jpg
(270.65 KiB)




I then turned my attention to a suitable jig to bully the workpiece to adopt the curve I wanted of radius 200mm.

Drawing it all out on a offcut of 18mm MDF, I then used the bandsaw to cut both the inner radius of 200mm and the outer one of 220mm.

Skids -photos 022.jpg
(276.77 KiB)


The holes are to allow the ends of F clamps to make the workpiece conform to the required shape. The might look a bit ramdomly placed but each lies on a radial line starting at the centre of the curve and evenly distributed along the circumference of the curve. The aim was not to have the holes too close together which could weakened the jig.

The smaller part of the jig was initially a single piece but this prove too difficult to use as it wanted to slide along the curve as the clamps were tightened. I was a nightmare with a dry fit let alone with glue. We all know how glue-ups get all the more stressful once the glue is applied and 3rd, 4th and 5th hands suddenly become necessary.
So in the photo is plan B the small block to the left can be clamped rigid to start with to control any left-right slippage and the crude link between the two parts acts as a hinge.

Skids -photos 020.jpg
(288.58 KiB)


First use the small block to clamp the straight portion of the work piece whith the block aligned to a pencil mark on the main part of the jig and the start of the wanted curve aligned to a second mark - apologies these have not come out that well on the photo.

Then with the reference points fixed the next clamp can be added and gradually tightened. Depending on how much threaded adjustment your clamp has you can use either a single clamp of alternate between two to take up the adjustment.

Skids -photos 018.jpg
(288.79 KiB)


One clamp will take it most of the way but to be certain I added a few more.

Skids -photos 017.jpg
(294.37 KiB)


I allowed best part of 24 hours for the glue (D4 PVA) to go off.

Once out of the clamps/jig the result looked like this.

Skids -photos 016.jpg
(262 KiB)


All I had to do next was make a second one.

I've written this part of the project in the tips and tutorials section and the rest of what I then went on to do will be in the woodwork section with a cross reference here
viewtopic.php?f=19&t=3822#p57662

Hope you find this interesting/useful

Bob
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Re: Laminating a curve - with a twist.

Postby Malc2098 » 23 Jan 2019, 19:01

:text-goodpost:
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Re: Laminating a curve - with a twist.

Postby Mike G » 24 Jan 2019, 08:44

Nice idea, Bob. I've laminated the entire length previously for similar bends. The only thing I'd say is that this technique is really only practically available to those with a table saw, because kerfs cut any other way would be too thin, and probably too rough, to be of much use.
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Re: Laminating a curve - with a twist.

Postby Rod » 24 Jan 2019, 09:28

Nice technique Bob

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Re: Laminating a curve - with a twist.

Postby RogerS » 24 Jan 2019, 12:07

That is so elegant, Bob :eusa-clap:
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Re: Laminating a curve - with a twist.

Postby Woodbloke » 24 Jan 2019, 12:48

Helegant it is :D - Rob
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Re: Laminating a curve - with a twist.

Postby TrimTheKing » 25 Jan 2019, 11:04

Very nice Bob.

:eusa-clap:
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