m2c1Iw
29th April 2007, 01:50 AM
How do you stop plywood from warping I've got the problem with everything from clear (handiply stuff) through to marine in sizes from 1/4 to 3/4. I do take a long time to make stuff but it seems you have to keep it stored flat and faces sealed which is a problem in my shop. Major :anoyd:
Mike
sinjin
29th April 2007, 01:25 PM
Store your sheets flat. But i agree it's just about inpossible to keep them from warping.
We used to buy ply by the pack and the top couple of sheets particularly on thinner sheets ie less than 6mm would always warp. The other reason is there seems to me that the vaneers are still quite green when they are glued up into ply form and so during the glueing and pressing process stress in the vaneers builds up.
Anyway i never really worried about it to much but working with nice clean flat sheets is always desirable.
echnidna
29th April 2007, 01:33 PM
store it flat with a chipboard cover sheet on top
Toolin Around
29th April 2007, 01:46 PM
Quality and the number of veneer layers does have an impact on movement in ply. The greater the number of layers the less the sheet will warp. Cabinet grade ply (not sure what you call it here) makes a difference as it is better seasoned and usually made up of more stable core veneers - but costs are much higher for it. I used to use a 3/4" meranti (sp?) ply that was very stable - stank something awful though.
soundman
29th April 2007, 09:30 PM
I've used my fair share of ply and also left plenty lying arround for long periods.
factor 1
ply with lots of stresses..... there are a couple of brands and types of ply that are terrible they'll warp in a full pack straped down:~
Slash pine is shocking.
I've ripped a sheet of slash up the middle and had the cut spring 10mm along the length of the sheet.....lots of stresses.... shets lo=ike that will warp with the slightest provication.
buy good ply that isnt prone to warping
factor 2
moisture.... if there is a difference between one side of the sheet and the other... almost any ply will warp...... a sheet of ply laid flat on a cement floor will warp as the weather changes.
keep your ply in a place where it has even moisture exposure on both sides.
This is why the top sheets of a pack warp...... never take the top sheet off the pack when offered by the timber yard.
factor 3
surface absobency imbalance..... ply laminated or finished on one side will be prone to warping.
I store my ply standing on edge packed with other sheet goods... it warps no more or less than flat.
there are all sorts of things that can be said and done but simply..... ply can not be trusted to stay flat of its own accord.
cheers
bitingmidge
29th April 2007, 09:37 PM
What Soundy says!
FWIW, I store mine vertically in a hinge-out rack, packed together so they don't lean at all.
http://www.woodworkforums.com/showpost.php?p=128847&postcount=47
Cheers,
P
m2c1Iw
29th April 2007, 09:55 PM
Good info, I use a rollong cart which stores vertically but still a problem might hae to add a veneer type clamp to hold em flat. Especially when I paid a fortune for some marine ply A facing both sides and grain running lenghtwise. Currently making a FFW ply tool cabinet and worried about the amount of distortion. over 5mm in 1200. Had to redesign and put a centre divider to correct.