One for the carpenters

[Tim Lamb]

An overdue project is reaching the pile top!

Our ancient Pine folding table, used for garden events, has exceeded all reasonable use by dates; being riddled with woodworm (treated), very heavy and exhibiting signs of protracted careless catering use.

I have in mind cannibalising the metal fitments and re-constructing the timber work using some sawn Oak scantling I have in store.

Apart from the increased weight my questions relate to the practicality of biscuit jointing 80mm wide planks to create a table top say

700x1700?

Is there a preferred grain orientation to minimise warping.

My stock of biscuits appear to be plywood. Are these weather proof?

Suitable glue. Aged sixteen, I made a display cabinet for my then girlfriends glass animals and nearly destroyed it by using powdered (one shot?) glue. Purple stains:-(

Any other thoughts?

[GB]

Ikea will sell you a table top for £15. It's smaller, and far lighter. It will survive a bit of light rain, although it is by no means waterproof.

[nothanks]

How thick are the boards? Assuming you have a jointer or jointing plane you should be able to get the edges flat so the only issue is preventing the pieces from rising-up when clamping. You either need a few of something like this:

or to arrange a flat and stiff board with a stop strip, wedges, cawls, clamps and weights.

Unless the wood is quarter-sawn (unlikely) then ensure the curved grain is alternated to reduce cupping.

Biscuits are cheap, buy some new ones. If you don't have a biscuit jointer you could use a loose tongue, rather than biscuits. Use almost any D3-rated glue, but I wouldn't use PU for this job.

Were the girlfriends very small, or was it a huge cabinet? ;-)

Don't fix the top rigidly to the base ... it needs to be able to move so use over-size holes for the hold-down screws (with penny washers) or provide slots. Do you know anyone in a joinery shop with a wide-belt sander? If not, unless you've accurately thicknessed the pieces and clamped them well during assembly, you might be in for a lot of scraping and sanding to get the top into a good condition.

It should be a satisfying project.

[The Natural Philosopher]

quarter sawn is what you want where the rings all are vertical. (assuming a horizontal table top) Wood warps by differential expansion and that occurs between the outer and inner rings of a tree. Quarter sawn merely varies its width, it doesn't warp Naturally the grain is very plain on quarter sawn.

Up to a point, yes.

I think possibly (mildly) foaming polyurethane glue for this. It will gap fill and waterproof. Clamp everything together hard though. My experiences with model boats in my youth suggest that it doesn't matter if the glue is waterproof if the wood is not

[The Natural Philosopher]

But it will be warped by the time you get it home, and rotted through by the year end.

[John Rumm]

ok

Depend on how it is sawn. Assuming it is flat sawn (the grain curves across the planks wide axis in an arc, the surface shows "cathedral pattern grain"), then invert each board so that the arc curves in alternate directions for each.

If it is quarter sawn (grain straight up and down) then it does not matter. Reft saw (grain at 45 degrees) then alternate again.

It is not going to matter much once they are surrounded by wood... (they need to swell a bit in the wet to work well).

All the biscuits need to do is assist with alignment when clamping up - they don't add any significant strength for this applications since there is already a substatial amount of long grain contact.

Any waterproof glue like Titebond III or Resin W etc. Sometimes marked D3. Clean up any glue on the surfaces with a damp cloth before it starts to dry though.

[Tim Lamb]

Existing 20mm. The scantling was sawn from a fallen Oak and roughly

90x85mm

No jointer. Usual technique has been to clamp several boards together and run through the planer. For gluing, I have a flat top work table and plenty of sash cramps

Ok.

Umm. I have a bench router and also a biscuit jointer.

Not heard D3 rating. I'll look it up.

Ha! Late '50's there was a fashion for collecting miniature model animals made of coloured glass. She got hitched to a BBC TV producer so it was a wasted effort.

Ok. I would have missed that!

I have a Startrite 12" planer so the thickness should be easy.

Might need transport wheels:-)

[RJH]

As an aside, the shop returns section in IKEA is pretty good for table top sized sheet materials. It's pretty rubbish (foil coated chipboard most of the time) but fine for basic shelving etc.

[GB]

That's just your prejudice. The £15 table top probably has a cardboard cell inner core, which won't warp. If it is kept dry, it will last for years. It will obviously fall to pieces if left out in the rain, though, and it won't take until the end of the year.

For use in 'garden events', it's not a bad solution.

[fred]

If oak is well seasoned it should make a good outdoor table. You are unlikely to have quarter sawn stock though some years back we did get a local forestry rip an 8ft log into quarter segments which we than transformed into 25mm thick planks on a band saw. Interesting exercise but I wuldn't do it again. Polyurethane glue is satans spawn. It may gap fill but gives no stregth to the gap filled areas. Use Cascamite. Excellent for outsoor use and has great gap filling properties. Beware those fancy outdoor pva glues. (I'm thinking of you Titebond) I made several projects with them and they didn't hold up well.

I found alternating the growth rings when glueing up wide sections unnecessary. One of thoe intrenet tropes which gets repeated ad nauseam. Yes I understand the theory but never found it necessary.

Standard biscuits are not waterproof any more than standard Domino loose tenons, as I discovered recently when swmbos clothes line table fell apart. The dominos had failed in many cases. They make exterior use ones but only available in long lengths at an exorbitant price. I ended up making my own out of oak.

[Tim Lamb]

Ah! The Oak was milled in the field using a mobile Lucas mill. A large circular saw is mounted on a portable frame and manually trundled along the length of the trunk. Long ago now and a mix of 90mm x 180mm, 90 x 85 and 180 x 25 were cut from various parts of the trunk. Boring finish it is:-)

[Tim Lamb]

I think, as has been suggested, the biscuits are more for positional benefit than permanent fixing. For smaller jobs, I have applied glue to mine. I'll consider routing a slot and using a full length tongue as an alternative. Cascamite? Is that still in use:-)

[The Natural Philosopher]

Opinions are divided. Like long welded rails keeping it in position with rigid conectors is fine when it expands. It will crack if it dries out more than when you screwed it down tho...

[Tim Lamb]

ISTR you venturing width expansion (across grain) being greater than length (along grain). I don't plan to leave it out in all weathers but it is bound to get some Sun.

[The Natural Philosopher]

IIRC shrinkage green to average indoor humidity is 1% along the grain, around 3% along the trunk radius and up to 7% in the circumferential direction The worse cut is a flat sawn plank the goes near the heartwood. The most stable plank is one that goes from the heartwood to the edge of the tree, if you can see curved rings, be careful

[TimW]

2'6" x 8' A standard table size, and much more fun to make one than buy one from worktops express or similar.

The way to do it depends on what tools you have but a few thoughts: I would not attempt to glue up 9 or 10 3" boards in one go. I might do two or three at a time then re straighten the edges, or add one at a time even. Reason being that required clamping pressure and issues of flatness and open glue time will make a single glue-up almost certainly a nightmare.

A straight router bit run along a straight edge is not a bad way to machine the glued edge. It will be nice and square, and you can always take another shaving off with a plane.

No biscuit required, glue plain butt joints.

Your top is not very thick, you might want to screw battens on the underside - screws in slots to allow movement.

Cleaning up the top surface is quite a lot of work. I would favour a hand held electric plane and learning to get a hand plane razor sharp rather than a belt sander which is a horrible job. A wooden plane can be lighter and less exhausting for that kind of job. Never sand then plane

- it will blunt your blade. A block plane with the blade slightly convex is the way to finish without leaving 'steps' from the blade edge. The oak will tear up and you must learn to love the hand finished look if you do it that way.

Waterproof pva is not a bad glue for this job. Or Polyeurethane, but beware the rapid curing time.

HTH TW

[nothanks]

That's quite thin for a top. TimW makes a good point about adding battens underneath to help keep it flat. Also, you could add a piece around the edge to increase the apparent thickness.

TimW has said that biscuits aren't necessary ... strictly that's correct but they make alignment a damn site easier if you reference them from the top surface.

Other thoughts:

- are you going to leave the ends as end grain? An alternative would be to add lengths of wood to the ends and mitre where they meet the outer lengthways boards. This looks best if the widths are made the same.

- had you thought about assembling the top as separate boards with small gaps between them? I have a garden table with a teak (!) top, between the boards is a gap of about 5mm - saves jointing and lets the rain water through, but needs a support frame.

- don't use steel screws in oak!!! Use brass or S/S.

So I presume you'll join boards to make three 10" wide panels, run them through the thicknesser, and then join the panels.

[Tim Lamb]

I'll take a view as the job progresses. Functional is the intention:-)

Yes. By far the simplest method. Bit tricky for cutlery as the purpose is outdoor eating. Also differential timber movement with exposure to sunshine. I expect Teak is much more stable than farm Oak.

Been there. Done that!

Excellent plan. I have been concerned about excess glue removal on the underside when assembling the strips.

[Tim Lamb]

Yes.

I've not done much hand held routing and would have to create a suitable guide. Previous technique has been to have waste material at both ends of the work such that a group can be secured together with screws. This speeds up the job and makes the work square.

Hmm. I purchased a job lot of imported hardwood advertised as lorry flooring. Turned out to be strips glued together to make up 12" wide boards. Sadly the glue has not stood up to use as agricultural trailer sides.

Indeed. Advised elsewhere.

This was a 250+ year old meadow grown tree so a fair bit of wavy grain from branches. I hope to get the jointing accurate enough for a sanded finish.

I still want to learn which glue goes purple on Oak.

[TimW]

On 10/08/2023 14:49, Tim Lamb wrote: [...]

I may have missed the context but steel/iron plus water plus oak will give you a very bad blue tanin stain. So wet pva plus a steel sash cramp will stain. Put cling film on the bar, or even newspaper. TW