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Should I sweat warped/twisted drawer bottoms?

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Forum topic by Sam_NY posted 01-14-2013 11:16 AM 930 views 0 times favorited 8 replies Add to Favorites Watch
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Sam_NY

3 posts in 686 days


01-14-2013 11:16 AM

Topic tags/keywords: drawers warp plywood

Hi all,

First post here, but lurker for a while…

My question: I cut some drawer bottoms for some large under-bed drawers (approx. 24W x 27D). I wanted something a little heavier, so I bought 3/8” ply and cut grooves in the drawer box. The ply (sanded pine from HD) has warped significantly since I cut them to size. Actually it’s more like a twist.

I’ve been weighting them down flat, but haven’t tried spraying with water, etc. I’m wondering if I should try to resolve before assembly/glue-up, which I guess depends on whether the drawer will force the bottom flat again or whether the warp/twist will instead to pull the drawer box out of square. Any thoughts? The drawer sides 3/4” birch ply and are about 8” tall.

Thanks for any advice.


8 replies so far

View Fred Hargis's profile

Fred Hargis

1985 posts in 1218 days


#1 posted 01-14-2013 12:36 PM

Those are pretty robust drawers, and I’d bet that 1/4” ply for the bottoms would have been plenty. I think I would assemble them and see…my guess is that the sides are stout enough to straighten out some minor twist. But if that 3/8 ply is doubled over you may want to make new bottoms.

-- Our village hasn't lost it's idiot, he was elected to congress.

View EEngineer's profile

EEngineer

906 posts in 2338 days


#2 posted 01-14-2013 02:07 PM

To me, with 24”W X 27”D X 8”H drawers, 1/4” seems marginal. I think 3/8” is more appropriate. However, as underbed drawers, they may never be subjected to as much load as, say, shop or kitchen drawers.

I agree with Fred, though – 3/4” drawer boxes are pretty stout. If you make them like traditional drawers, i.e. dado or dovetail at the drawer front and back dadoed into the sides with the drawer bottom slid into the grooves at the drawer bottom after the box has been assembled, I don’t think the bottoms will cause the drawer to warp.

Plywood doesn’t move much at all with changes in the seasons or humidity. I would consider gluing the drawer bottom in, also – don’t leave it floating like most drawer bottoms.

-- "Find out what you cannot do and then go do it!"

View RussellAP's profile

RussellAP

2963 posts in 1011 days


#3 posted 01-14-2013 03:21 PM

It’s a pretty stout design using 3/8 ply, but if you have room under the bottom, I’d span the 24” width with a piece of hardwood for support. 2 feet is a lot of room for heavy clothes and it will eventually warp it without some support.

-- A positive attitude will take you much further than positive thinking ever will.

View Sam_NY's profile

Sam_NY

3 posts in 686 days


#4 posted 01-14-2013 03:38 PM

Thanks for the replies. I was up in the air about whether to go 1/4” or 3/8” for the bottoms.

EEngineer, that is how I constructed the drawers: dadoes front and back with grooves cut for the bottom. I was thinking about gluing the bottoms as you suggest to help keep everything rigid.

I just put one together dry and it occurs to me now that once fitted in the grooves, most of whatever pressure from the warp is probably exerted on the groove itself, not the joints, if that makes any sense. Anyway, since it seems okay dry, guessing I’ll be safe once it’s glued up. Just being paranoid…

Thanks again for the advice.

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Sam_NY

3 posts in 686 days


#5 posted 01-14-2013 03:49 PM

Russell: I did leave a little extra space beneath the groove just in case I decided to do that. Certainly can’t hurt!

View MrRon's profile

MrRon

2937 posts in 1968 days


#6 posted 01-14-2013 08:32 PM

Replace the bottoms with 6mm Baltic Birch plywood in a 1/4” wide dado.

View Loren's profile

Loren

7809 posts in 2373 days


#7 posted 01-14-2013 08:36 PM

Put a drawer together dry to see if the bottom twist is
strong enough to twist the drawer.

Ball bearing slides can prevent a drawer from twisting.

I don’t think an out-of-flat drawer bottom in your situation
is likely to be a deal breaker, but it depends on the
fit tolerances you are working to.

-- http://lawoodworking.com

View pintodeluxe's profile

pintodeluxe

3515 posts in 1538 days


#8 posted 01-14-2013 09:03 PM

If the drawer bottoms are to be assembled into a groove in the sides, assembly will likely correct most of your problem. When you groove the drawer parts, you might aim for a slightly loose fit to give yourself some wiggle room during assembly.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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