Edge Joining

[garryjc]

I have been trying to join timber to make a wide flat board. Sometimes all is fine, but more often the wood cups and I do not have the desired flat board. I use a jointer that I beleve to be square. Biscuits and firm clamping.

How important is it to alternate the growth rings?

The timber is from a local Mitre 10, usually KD.

Any thoughts?

Thanks

Garry

[BobL]

Hi Garry,


I have been trying to join timber to make a wide flat board.
Presumably you mean something like a wide table top?
Also, how wide and thick are the starting boards?


Sometimes all is fine, but more often the wood cups and I do not have the desired flat board. I use a jointer that I beleve to be square. Biscuits and firm clamping.
Do you mean the whole table top cups or the individual boards in the table top?


How important is it to alternate the growth rings?


Alternating the growth rings helps but if they are quite wide boards to start with and continue cupping back and forth as the moisture levels go up and down then your top is going to have a lot of movement and could eventually destroy itself. One way to handle boards that cup significantly is to rip the boards in half and assemble them in alternate fashion.

KD can mean over dry or dried too quickly and the boards need to recover before use. Before making something like a table top I would leave the individual boards for a couple of months or more in the shed and see how much the individual boards move in that time. Individual boards that move a lot in that time may be rescued by ripping in half or thirds but may also be best left out of the top.

It's hard to do but buying timber that has the growth rights at much at right angles as possible and not parallel to board width reduces these problems.

[Wongo]

I reckon it doesn’t matter what you do, the top will still cup sooner or later. The important thing is to attach the top to the base quick smart and allow it to move at the same time.

[garryjc]

The board warps, not the individual boards.

I wanted to make sides of a case from solid wood. The sides were to be 700 h x 500 w x 19. It seemed impossible to get KD flat sides. If the timber didn't warp before I started the panels seemed to look like a half moon whortly after they came out of the clamps.

Should I use narrower boards? I used 2 x 200 and 1 x 100. Would 6 x 100 be more stable?

Any ideas would be appreaciated!

Garry

[davo453]

I can't say I've had any trouble with cupping once the board is attached to the base.

I always use traditional techniques to make furniture which allows for natural wood movement.

I have pre made boards and had them cup while in storage. storing them flat with a weight on top helps a lot.

I always make my boards with alternating growth rings and don't really worry about their width or thickness.

I use mainly recycled timber these days and as that is generally very dry it doesn't move much at all.

Cheers


Dave

[BobL]

The board warps, not the individual boards.

I wanted to make sides of a case from solid wood. The sides were to be 700 h x 500 w x 19. It seemed impossible to get KD flat sides. If the timber didn't warp before I started the panels seemed to look like a half moon whortly after they came out of the clamps.

Should I use narrower boards? I used 2 x 200 and 1 x 100. Would 6 x 100 be more stable?

Any ideas would be appreaciated!

Garry

To avoid confusion lets call a set of boards glued together a panel. If you take the panel out of your clamp and it immediately bends this means the whole panel is under tension suggestion poor jointing. How do you joint the boards? - do you joint them in pairs and then open them out like a book with the jointed edge as the hinge? This aligns the edges even if they are a bit out of square. This would also be consistent with panels bowing different amounts.

[rightendup]

I'm with BobL,
Either the doubling up of boards through the jointer or write an 'F' on the side of the board that touches the fence, on glue up you would see the 'F' on the face of every other board.
And yes, narrower boards make better panels but not necessarily more attractive panels.
Often, especially on smaller jointers, if the wood has not gone through the table saw with a good edge to start with it will never be corrected by jointing, for good jointing you need a good table saw with a long fence (like the Biesemeyer)
For really good edge gluing one first joints through the jointer and then follows with a joiners plane, mine is 16" long Record (took 14 solid hours to flatten the sole!) to this I clamp a maple 8 quarter block that is rabbeted which keeps the hand plane from tipping left or right - invisible glue joint results.

Jay