Total novice here - glued a panel for a table and there is some cupping/not flat. Any advice on getting it flat & avoiding this for my next project?

[Dan James]

I thought I would take up a little woodworking as a hobby for my spare time - it has always interested me and I need a new coffee table, so I thought why not start off with that?

I spend a good few quid on a bunch of tools and clamps and took a trip to the local timber merchant for some 100x25 PAR redwood which I cut to size, doweled (I have since found out dowels are not needed except with MDF) and glued it securing in clamps. It's real sturdy but it isn't flat - I have discovered that one of the lengths I got had a nasty twist, far left board in the below image is so twisted it doesn't lay flat so both sides need work I think. In this situation, how do I work with what I have? Would this be a job for a plane? looking for any advice!

 

[Hornbeam]

2 things to consider
Timber will always move a bit. Looking at the ends of your boards, the growth rings always tend to straighten out during drying. You can either alternate the boards or accept a gentle curve which would be pulled flat by the underframe of the table
Also look at the planed edges of your boards if they are slightly out over 25mm they will be out a lot more over a couple of joints/board widths. Dont use the planed edge as supplied by the timber merchant. squareness is definately not guaranteed (or expected)
Dowels may not add a lot to the joint strength but they help with alignment and stop everything slipping around while clamping up
Ian

 

[recipio]

Don't beat yourself up -- it happens to all of us. Cupping is likely if the growth rings are all the same orientation, especially in pine. Not having a true right angle between face and edge is another problem. Dowels and biscuits help keep the boards aligned but must be accurate. I wouldn't start to plane the top - you are just creating a tapered ' wedge '
Assuming you are going to use rails and legs you might just get away with using 18 mm threaded inserts to hold the top down using a bracket or just drilling straight through the rail. Clamp the top down while inserting the M6 bolt - it should hold whereas a simple screw will not.

 

[HOJ]

Presume you haven't prepared the timber other than dowelling it and gluing together, as @Hornbeam & @recipio say, don't expect off the shelf par timber to be perfectly straight or square, you still need to dress them if your going to make things such as this, so a plane is pretty much an essential (that opens up a whole different debate). worth having a look for @custard's post about Edge jointing boards:

You could plane the top flat, or even sand it but the underside will need to be done as well, so you're going to lose thickness from 25mm if that's what it is now.

 

[Fergie 307]

Personally if the width isn't critical I would probably run a saw down the joint between the second and third board from the left to separate them then redo that joint, you should only lose a few mm. Looks as though the two on the left are aligned with each other, and those on the right look ok, it appears to be that second joint that is the problem. Maybe that the edges were not at right angles to the top on that joint. Important when you glue up to ensure that the piece is held flat while the glue sets. And always check the joint dry first, so place the two pieces together and make sure they are correctly aligned, ideally on a flat surface, before you reach for the glue. And I would use biscuits or dowels, they will help keep the boards aligned. If you haven't got a jointer, and don't feel confident with a plane then you can get the edge at right angles using a router. Just clamp a long straight edge to the board at the correct distance from the edge and then run along it with a straight cutter, that's if you have a router of course