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Joining a bent lamination

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Forum topic by Dorado posted 03-15-2013 09:47 PM 985 views 0 times favorited 15 replies Add to Favorites Watch
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Dorado

5 posts in 586 days


03-15-2013 09:47 PM

I’m in the process of making a coffee table top that is the shape of a right triangle. The three corners are rounded into a 3” radius. The edges of the top are trimmed with 3/4” x 1 3/4” Red Oak to create a thicker looking top to the table. The corners edge banding will be bent laminations made up with layers of veneer. My first question is: Has anyone had success with 1/16” or 1/24” flat cut Red Oak raw veneer around this radius?

My 2nd question is: What kind of joinery would be best to join the ends of the arcs to the ends of the strait edge banding? I have thought of Dowels, Biscuits, and even a running dove tail. I not sure if the plastic resin glue used with the laminations would be a factor or not.

Work Safely!

Dorado


15 replies so far

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SCOTSMAN

5421 posts in 2273 days


#1 posted 03-15-2013 09:48 PM

Mortice and tennon or similar. Alistair

-- excuse my typing as I have a form of parkinsons disease

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SamuraiSaw

464 posts in 652 days


#2 posted 03-15-2013 10:06 PM

I’ve not had good luck bending oak, especially that tight a radius. Oak is such an open grain, it has a tendency to split. If you’re steam bending, oak doesn’t like moisture and has a tendency to turn black.

Have you thought about making the radiused corner out of solid stock, say poplar, and putting Oak veneer on the radius? That would give you a clean look and allow you to create a solid joint with the skirt.

-- Artisan Woodworks of Texas.... www.awwtx.com

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Woodendeavor

222 posts in 1294 days


#3 posted 03-15-2013 10:15 PM

I have built shaker boxes from oak 1/16 thick on a radius of 2 1/4”. I have to be careful to pick straight grain but it is possible

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SamuraiSaw

464 posts in 652 days


#4 posted 03-15-2013 10:20 PM

Do you steam the wood?

I’ve had a little better luck with rift or quarter sawn, but I’ve never had good success with plain sawn oak.

My technique needs some help.

-- Artisan Woodworks of Texas.... www.awwtx.com

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404 - Not Found

2544 posts in 1657 days


#5 posted 03-15-2013 11:31 PM

What is the table top made of and how thick is the table top (1 3/4 is the height of the banding right?).

If I understand this correctly, you are attempting to give a beefier look to your top by adding a combination of bent lam corners and straight pieces. Sorry to poo poo your idea, but I can’t see it working. To get a seamless join between the top and the banding at the round corners, you would need to laminate them directly onto the edge of the table top, to do that, the table top will have to made the finished thickness you desire – if it’s made of veneered mdf for instance, you could double it up, maybe put in a different thickness plain mdf as a filler to get the desired thickness (eg 3/4 1/4 3/4) and trim it all up using a template cutting bit to get the edges perpendicular around the perimeter and the full depth. Then start laminating. Now that’s going to be a problem as well. Look at some commercially made round tables, they are edged not in segments as you suggest, but with continuous lengths overlapping and tapering at the joins so you don’t see lots of butt joints – which is what you will have with what you are proposing. I would be thinking in terms of wrapping pieces of laminate around the whole table to achieve a seamless edge, and with the radius being tight, and the timber being oak, I don’t know if that is achievable. In hindsight, you probably would have been better off edging a plain mdf full depth top first, and veneering on top of that, or making it out of solid timber altogether.

Are you routing a profile onto this table edge? If it’s just a straight edge – contemporary look, you could use 2” iron on edging – but again, the table top would have to be the desired thickness all the way around for the iron on edging to stick to.

If you are still going to try making three curved corners, you can give your thin material a pre-bend where it needs it by covering the area you need to bend with a wet cloth and put a hot iron on it for a few seconds, leave the iron on til it’s crackling and spitting, take the iron off, bend the piece around something and allow it to cool.

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runswithscissors

1010 posts in 713 days


#6 posted 03-16-2013 12:56 AM

You can easily bend 1/8” or even 1/4” oak to a 3” radius by using heat. No need for steam or any moisture. The thicker the wood, the more you need a bending strap around the outside of the bend. Wide banding from the lumber yard’s dumpster is good for this. Clamp one end in your vise, the other end with a C clamp, and heat the area you want to bend (and a little beyond) with a heat gun. Be careful, as you can easily scorch the wood with a heat gun. Within a 3 or 4 minutes, 1/4” oak should be ready to bend. Bend gradually, keeping the heat on.
I always have good luck bending by eye, and overbend because there will be some spring back. With wood as thin as your contemplating, the heating should only take a few minutes, and the cooling only a minute or 2. After you have bent the number of laminations you need, you can nest them and glue together. Obviously the inner plies will need a little tighter bend. I’d clamp this layup around a form until the glue dries.

Oak is one of the easiest woods to bend with heat. You could do the corners separately as you were planning, or use long enough wood to do all 3 corners, with a butt or scarf joint between 2 of the corners.

A lot of people will tell you you can’t bend without moisture. I have been doing it my way for years, for many different projects. Try it. You might be surprised how easily it works..

Geez, maybe I should do a blog about this.

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404 - Not Found

2544 posts in 1657 days


#7 posted 03-16-2013 01:04 AM

rws, I have seen it done on the flue of workshop stove, but as I haven’t got a workshop stove, have never tried it.

View Loren's profile

Loren

7734 posts in 2336 days


#8 posted 03-16-2013 01:32 AM

Bending veneers to a 3” radius should present no
big problems.

You might pre-bend the first few on a hot pipe to get
the shape you want. After 3 layers are laminated up,
the rest can be laminated one at a time with no pre-bending.

-- http://lawoodworking.com

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Dorado

5 posts in 586 days


#9 posted 03-16-2013 03:53 PM

Woow, such a great response to my thread, and I thank you all.

My table top is 3/4” thick and my edge banding is an attempt to get a beefier look as stated above. The bent laminations are merely layers of dry veneer. These are not steamed or soaked in any form, and heat is not used via the technique I was suggesting. The laminations would be layered with a plastic resin glue with a fairly long open time and clamped to the 3” radius mdf form with cauls. Of course the form and cauls are taped to prevent advertent adhesion.

RWS and Loren suggested heat bending the oak using 1/8” or 1/4” material using a heat gun and pipe. Do you need to use straight grained quartered sawn wood to this?

I’m starting to realize that trial and error with an experimental mind set could be one approach that would answer a lot of questions and prove to be useful. Can’t hurt.

Has anyone tried a sliding dovetail to join the ends of the arcs to the straight edge banding?

Work safely! Dorado

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Loren

7734 posts in 2336 days


#10 posted 03-16-2013 04:31 PM

Yes on the straight grained, no on the quartered. Grain runout
can be a problem. 1/4” can be bent on a hot pipe though that’s
pushing the limits and I recommend a backing strap.

You inquired about bending veneer 1/16” or 1/24” thick. The
thicker you go the trickier bending becomes.

The thickest I bend on a hot pipe is usually 1/10” or so. Any
thicker is pushing the process and operator skill, though
personally I believe well chosen stock up to about 3/8”
can be modestly bent on a pipe. A 3” radius is not
a modest bend.

If the curved parts are not structurally loaded like legs
or chair parts, you might consider doweling rounded
corner pieces into straight skirts, then veneering
the outside face.

-- http://lawoodworking.com

View levan's profile

levan

411 posts in 1667 days


#11 posted 03-16-2013 09:00 PM

My prefered method would be to use tite bond II. Apply glue to both surfaces, let dry, start at one end of the veneer and simply iron it on. A ordinary household iron. Straight grain is nice but try out a sample. I would just veneer the entire table edge, you can just use a backer that is atached to the top all the way around. TRY IT YOU WILL LIKE IT.
best wishes

-- Lynn "If you think you can do a thing or think you can't do a thing, you're right". Henry Ford

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runswithscissors

1010 posts in 713 days


#12 posted 03-17-2013 11:44 PM

1/4” X 1 1/4” oak. Bent to 3” radius. Included angle between arms is slightly narrower than 45 deg (one of the corners of a right triangle). Heat applied for about 4 1/2 minutes. Cooled about 2 minutes. The bending strap is lying across the arms (1 1/4” wide, which limits width of the stock I could bend). It is a piece of banding from the lumber yard’s dumpster. Heat source was an infra-red propane powered paint stripper. A heat gun would work as well, but scorching is more problematic with it. Except for a cardboard template cut to the 3” radius, this was a completely freehand bend. To alter the bend (including straightening it out), it would need to be re-heated, which can be done, in spite of assertions to the contrary.

No moisture used at all. This is a salvaged piece of oak from a piece of trim, and therefore can be assumed to be very well cured. Straight grained, but paid no attention to whether it was vertical grained or flat grained before bending. Makes no difference in my experience. (Checked it after bending, and it was semi-vertical grained, angled at about 35 or 40 deg. from vertical).

A bend like this is virtually permanent, with no built in stresses like a lamination. That is because the grain structure of the wood is physically altered, the fibers on the inner part of the curve sliding past each other and folding in on themselves (in extreme bends, this may happen radically, which to me spoils the results). Upon cooling, this new orientation of the fibers is “frozen” into place.

If I were building your table, I would do the bending first, then scribe the inside of the bend onto the table top material. Easier to get a precise fit that way.

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SamuraiSaw

464 posts in 652 days


#13 posted 03-18-2013 12:13 AM

”Geez, maybe I should do a blog about this.”

I think you should!!!

-- Artisan Woodworks of Texas.... www.awwtx.com

View Dorado's profile

Dorado

5 posts in 586 days


#14 posted 03-18-2013 02:28 PM

RWS

Woow, great pic and detailed explanation. I agree with your last statement concerning the scribe technique. So… I have a lot of great ideas brewing here and need to get busy making sawdust. I’ll be back and let everyone know how I made out.

Work safely

Dorado

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runswithscissors

1010 posts in 713 days


#15 posted 03-18-2013 08:22 PM

Another thought: You could make a template, say from 1/4” hardboard, to fit that inner curve exactly. Scribe the curve onto your table top, and cut to outside the line. Then use the template with top-bearing pattern cutting bit in your router to trim it to a precise fit.

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