Thread: Is a profile necessary?

It depends on how straight the boards are.
Strength wise there's no need for a profile but it sure helps when gluing up to have quick reference points to align the boards.
Often a few biscuits is all that is needed.

For a 2.5 meter long table that is also 1 meter wide, I would put something in there to align the boards. whether it be dowels, dominos, biscuits, or the double F joint. My preference would be for the double F joint assuming I wasn't worried about how the end grain glue joints would look AND I have enough material to account for the ~5mm/board I lose due to the profile.

You can glue up the top without any alignment aid by gently applying some clamping pressure and tapping the boards into alignment with a rubber mallet. This is what I usually do for smaller glue ups of 5 boards not more than 1200mm long. Or you can use "clamping cauls" but they suck imo, more trouble than they are worth, and don't work nearly as well as the "tap tap tap with a mallet" method.

Thanks for the help.
At the end of the project I'll either out up a pic of the table or a pic of the fire that the wood became.

Hi Mike,definitely agree with Bob and Kuffy.
Edge to edge gluing is perfectly acceptable without any fancy profiling when using Modern Pva glues etc,have never had any boards separating.
using biscuits or dominoes certainly helps align the boards both vertically and laterally and reduces the amount of time needed to dress the glue-up afterwards.

Plain well jointed boards are much easier to work on if there is a problem as well, with or without biscuits or dominoes . I've got this in as a restoration job at the moment . The only way I cold fix the top is saw it to pieces and then be a fair bit short on timber to make up for the lost wood. I think we are just going to leave it and give a repolish as is . It's up to the client to decide that .

Rob

Apart from the alignment issue the use of a profile on a glue edge is also because it increases the glue area.
Regards Rod.

Originally Posted by Rod Gilbert

Apart from the alignment issue the use of a profile on a glue edge is also because it increases the glue area.
Regards Rod.

It's true... A double F or similar profile like what is shown in Robs photos on the previous post more than doubles the glue surface and hence the strength of the joint. BUT As Robs photos also demonstrate, this does not mean that the joint will withstand the ravages of time. Also if the boards are cupped or warped even a little this sort of joint is tricky to make ... they are tricky at the best of times.

Table top joints do not need to be very strong. They are just holding the boards together. Butt joints are strong enough for this purpose.

Splits joints such as those in Rob's pictures are probably due to chemical degradation of the glue with time and/or stresses at the joint due slight differences in swelling and warping of each board with temperature and moisture.

Whether you profile or you don't - my advice is don't skimp on the glue - either in quality or in quantity - and don't be tempted to clamp so hard that all the glue is squeezed out. Some oozing is desirable (it tells you that there is enough glue covering the whole surface). Excess glue forms a bead when dry which can be easiy removed with a sharp chisel and then sanded (I find this better than wiping with a wet cloth before the glue dries).

Hope this helps...

Jorge

20 or more years ago I would have joined boards with biscuits. I look back now and recognise that it was not necessary. I have since simply butt jointed all and, as Kuffy mentioned, tap tap them into alignment. It needs to be noted, however, that planing the top is second nature to me, and this may not be everyones cup of tea. I cannot imagine having to sand a top flat.

My experience with profiled tops - such as tongue and groove joints - is that this adds an extra area in which one must take care. Not only must the edges be jointed flat, but the machining of the joints then must be accurate. Any deviation will show up as a gap. An alternative to a T&G joint is a spline. I think this is too much effort.

It has been shown that biscuits (used to align boards) can telegraph through to the surface in time, showing up as deformaties. This is enough to forgo using them. I purchased a Domino 500 a little while ago for a kitchen build. It occurred to me that the smallest domino is a fraction of the size of a biscuit. Perhaps these can be used to better align boards.

I believe that the secret to a flat top is to glue up immediately after jointing and thicknessing. Leave the thickness slightly over the planned dimension. Use decent clamps that you are comfortable setting up, and do so on a flat surface. Use the floor if necessary. Tap boards into alignment. I use cauls along edges as the clamping pressure may not extend there. Use a decent glue (I stick to Titebond as it is a familiar entity). I generally only glue one side (but liberally) - because it is less messy than stacking boards with glue on both edges - and then rub the boards together as they lie on the clamps. I wipe off excess glue with a wet rag (some don't agree with this, but I have never experience a problem with the finish - in any event, I handplane all surfaces).

Regards from Perth

Derek

Originally Posted by derekcohen

.....Use decent clamps that you are comfortable setting up, and do so on a flat surface. Use the floor if necessary. Tap boards into alignment. I use cauls along edges as the clamping pressure may not extend there. Use a decent glue (I stick to Titebond as it is a familiar entity). I generally only glue one side (but liberally) - because it is less messy than stacking boards with glue on both edges - and then rub the boards together as they lie on the clamps. I wipe off excess glue with a wet rag (some don't agree with this, but I have never experience a problem with the finish - in any event, I handplane all surfaces).

Regards from Perth

Derek

I think this is good advice from Derek... I made these cheap sash clamps that clamp down on the boards being glued from both sides (link below).

Home made sash clamps made from cheap pine short cuts

I have never used them on something as big and as thick as a table top, but the results is invariably a very flat board that requires NO planing and a minimum of sanding. Cost me ~ $20 for a set of three (pairs) and I've used them several times. I think they work better than store bought pipe or sash clamps, and they are so cheap it's embarrassing.

Enjoy the project....

Originally Posted by GarciaJ

I think this is good advice from Derek... I made these cheap sash clamps that clamp down on the boards being glued from both sides (link below).

Home made sash clamps made from cheap pine short cuts

I have never used them on something as big and as thick as a table top, but the results is invariably a very flat board that requires NO planing and a minimum of sanding. Cost me ~ $20 for a set of three (pairs) and I've used them several times. I think they work better than store bought pipe or sash clamps, and they are so cheap it's embarrassing.

Enjoy the project....

Have you planed a slight curve on the clamp faces or have you just left them as is?
Cheers

Originally Posted by Lappa

Have you planed a slight curve on the clamp faces or have you just left them as is?
Cheers

Left them as is. The pressure on the face and back of the "job" does not need to be high. Actually i think it is far better for each sash to be perfectly straight... otherwise you might end up with a cupped laminated board.

If you are concerned about clamping pressure you could put a build up of green packaging tape where the lats and the sashes intersect.... I've not bothered...