1/4" ply strength

[chopnhack]

Does anyone know how to simply calculate the strength/load capacity of 1/4" plywood (assume weakest species/ commercially produced ply). I am building some pantry drawers and using 1/4" for the bottoms and was curious as to the strength. The drawers are small at 15x13 so I don't think I'll have a problem, but was really curious as to how to figure this problem out. The drawer sides will be 3/4 birch cheapo HD ply with 1/4" dado's 1/2" up from bottom edges.
Thanks for any info.

[Pappy]

Actually you are going into overkill with the drawer sides. 1/2" Baltic Birch is plenty strong and better ply than the crap from the Borg. Supported in dados on for sides, or even 3 with the bottom tacked to the rear piece from the underside, you should be good with 3/16" ply for the bottoms.

[cabinetman]

Actually you are going into overkill with the drawer sides. 1/2" Baltic Birch is plenty strong and better ply than the crap from the Borg. Supported in dados on for sides, or even 3 with the bottom tacked to the rear piece from the underside, you should be good with 3/16" ply for the bottoms.

I agree, 3/16" for that size drawer is adequate, 1/4" would be better. For sides, BB in 1/2" would be best if plywood, or any 1/2" hardwood plywood. I've used 3/4" in a jam, it does look a little heavy, but will make for a strong drawer. If the bottom fits in a groove, and is captive with the back of the drawer, or gets fastened to the underside of the back, cut it so it squares the drawer when inserted. Hold the drawer square when fastening.
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[JimD]

You could google "sagulator" and calculate deflection like the bottom was a shelf. It would not be completely accurate but would be conservative.

I agree that 1/4 is enough as long as the drawer is not real deep with heavy stuff in it.

I normally use 1/2 BB dovetailed on all 4 corners for drawers. Drawers for clothes are 1/4 plywood bottoms as are kitchen drawers up to 6-8 inches deep. Deeper kitchen drawers get 1/2 BB bottoms. This is not based upon calculations, just a little experience plus hopefully some common sense.

Jim

[sscherin]

The last drawers I made were 17x17 OD, 3/4 sides (I had it laying around)
1/4" Hardboard bottom in a 3/8" deep dado 1/4" off the bottom of the drawer sides.
Interior Depth was about 5"

They passed the small child test. (about 25 lbs)

[ironhat]

The last drawers I made were 17x17 OD, 3/4 sides (I had it laying around)
1/4" Hardboard bottom in a 3/8" deep dado 1/4" off the bottom of the drawer sides.
Interior Depth was about 5"

They passed the small child test. (about 25 lbs)

Didn't s/he cry when you closed the drawer?

[chopnhack]

ah, awesome thanks for the info all. The sides are 3/4 only because I had a lot left over. I will be dado'ing all four sides - I am going to try my luck with a lock miter bit in the router for the joining of the drawers edges. I think that if I get the "set up" down it should make for some really strong joints when glued up. The back will simply be screwed on - in case the wife over loads one of these drawers Its for a kitchen pantry right off of the kitchen in a hallway closet so if i really botch the job, it will be hidden!! I hope it comes out good -- if it does i get to do another couple neat jobs in the house which equals tool purchases!!!!!