I bought a 4×8 sheet of 3/4″ plywood that I thought was straight and had the store basicaly quarter it. All 4 pieces have a slight curvature. Could they have curved after the cutting? Can they be straightened? I am trying the tried and true 3 block method.This is going on top of an island so I can place a top of african limba wood on top. Even if I get this straight will it pop back up becasue I would be gluing it into particle board?
Worse case I think I can return it to HD, 2nd time around how do I ensure the 4×8 is trully straight?
Replies
Welcome to the world of plywood. What grade of wood did you buy?
The stuff at the home centers isn't furniture grade and most of it is warped.
It's not a big deal if its going to be fastened to framing or backing as it will straighten itself out.
Your piece in the photo's looks great. Did you build it yourself?
It is not unusual for plywood to warp some due to moisture changes.
One thing you can do is install some glue blocks inside the top of your cabinets. should fit over the tops of your drawers. (glue and screw them into the cabinet face/sides/back)
Then you can screw the plywood into the solid wood you use and it should stay where you want it.
https://www.engineeringtoolbox.com/wood-screws-allowable-withdrawal-load-d_1815.html
number 10 flat head wood screws through a 3/4 inch glue block would hold up to 80 pounds per screw.
Is your subtop necessary? How thick is your limba wood? You mention glueing to particle board, is the limba wood a veneer with a particle board core?
I ask because if your limba is solid wood but only 3/4”, I’d forego the ply and just build up the edge with the same wood along with strips to match fastening points below.
Also, if solid limba you don’t want to fasten that “solid” to the cabs. While you can screw it down tight from below, you”ll want a slightly larger diameter hole than your screw shank , in your cabinet mounting blocks . This will allow some lateral movement of the limba top so it doesn’t split from seasonal movement.
Maybe....
#1 Off the rack plywood. I didn't evenknow their were grades.
Cabinets are standard sink base from Lowes - Hickory. I went to a lumber store to buy more "hickory" to make the top and found most isn't figured. I looked again at the bases and most faces are glued up from 'good' figured hicory. I'm happy.
#2 glue blocks would solve the problem which is a cool solution that leads me to # 3
#3 I had granite installed on another part of kitchen and 5/8 plywood base was required. I (mistakenly) assumed it was requried for all countertops. Shows what thinking will get you. Anyway I wondered why not glue directly? Its not like its going to break. At 3/4" I did glue another 3/4" around the perimeter on the bottom to give it a thick look. I'll have to dry fit to see if my drawers will slide out.
Don’t forget.
Also, if solid limba you don’t want to fasten that “solid” to the cabs. While you can screw it down tight from below, you”ll want a slightly larger diameter hole than your screw shank , in your cabinet mounting blocks . This will allow some lateral movement of the limba top so it doesn’t split from seasonal movement.