Finding vertical load of plywood

[Brian Parker]

I understand that the strength of plywood depends on the size of the piece along with the amount of layers. Does anyone know any formulas or webpages that would help me find how much of a vertical load that plywood would hold.

I ask since I am making a cabinet for my new edge sander and I have alot of 1/2" laying around and want to use it but I want to be sure that it will hold the 200# sander and other stuff. I'll proabibly make the base have drawers so there is another good 100-200#'s of weight to hold. I have no problems using 3/4" but I'm more curious of my options. I'll be placing all of the load onto casters so I can move it around too.

thanks
Brian

[Ray Bersch]

Brian, try this link http://www.apawood.org/ you may have to fish around or refer to some publication that is mentioned on the site to get what you want. But when you find it you may not be able to apply it directly to your application.

On the other hand, just keep in mind that boxes are a rather strong design and it is easy to add reinforcement to sides - using 1x or by ripping some plywood and gluing/screwing it to the sides to improve vertical strength - or just double up the 1/2" stuff. Add support beneath horizontal spans to prevent sag and be sure your connections (sides to back, bottom, top etc.) are strong. In other words, over build the thing rather than try to decipher the engineering stuff.
Ray

[Brian Parker]

Ray, (or anyone else who would like to chime in)

I am looking to build a cabinet for my new G1531 6" x 80" Edge Sander. I figured that I could take the $100 that I saved by not buying the one with the base and make a nice base. I have some old kitchen cabinets from my parents house that arent being used. I have some 30" bases and I think a 36" also. They are 1/2" plywood sides. I am thinking of taking them apart and gluing up a piece of 1/2 or 5/8 OSB to the inside of the pieces. Do you think this is stronger than a sheet of 5 layer 3/4 inch plywood? I should note that the 1/2 ply from the cabinet is 3 layer.

any insight would be great, since the sander alone is 200#'s

[Don Baer]

The cases for my work bench are made of 3/4" Plywood. I have one of these sittng on the bench top.

http://www.harborfreight.com/cpi/photos/46100-46199/46199.gif

It wieghs in a 332 lbs and has been sitting there for 10 years. I made sure that it was sitting directly over one of the walls of the cabinate but it seems fine.

[Kent Parker]

Brian,

Rather than take things apart, consider adding to what is there to accomodate the downward (compressive) load. How about adding internal cleats to the sides or you could call them vertical frames if you like. Say two or three hardwood pieces about 3/4" x 2" with the 3/4" side against the plywood skin. It will add substancial stiffness to the panel by decreasing the loaded panels dimension.

Nice name by the way.

Cheers,

KP

[Doug Shepard]

I think maybe this is what you're looking for
http://www.woodbin.com/calcs/sagulator.htm

[Norman Hitt]

I think maybe this is what you're looking for
http://www.woodbin.com/calcs/sagulator.htm

I may be wrong, Doug, but I think he is wanting to know the load carrying ability of the Vertical pieces, ie; Cabinet ends and dividers, etc.

I would like to know a good resource for this information also, as I've agreed to help a friend build a cabinet base for his new large aquarium, in my shop, and we've calculated that by the time the glass aquarium, water, rocks and fish are all added up, there will be approx 1500# sitting on the cabinet. Me-thinks we will need to do a LOT of internal bracing in this cabinet, and I'm very concerned about Racking.;)

[Larry Reimer]

The site that Ray brought to our attention has very good information. If you search on the site for their publications there's one for plywood design specifications. It's available for free download. Will tell you how much load plywood can handle when the sheet is put in compression on edge. There's also a bunch of other good info there.

[Brian Parker]

I've checked out the site that Ray mentions and I'm not sure which PDF files you are talking about. I tried to register for the site but I have not recieved anything in my e-mail account stating what to do next.

[Ray Bersch]

Brian, sorry you could not find what you needed. But I still think you are trying to over-engineer your cabinet. I believe there are two areas that should concern you. 1) the connections and 2) the unit may be top heavy.

As Kent suggested, use your old kitchen cabinets and beef them up. You don't really need hard wood for your vertical supports if you don't want - remember your house is made with 2x4's. It is the integrity of the box as an assembly that is important, not necessarily the strength of each component (no rocket science comments, please, we're talking about a wood base cabinet here.) So, add a 2x4 at each inside corner, screw through the plywood (using pan head or washer head screws - I like square drive screws) from the outside on sides and back and through the face frame on the front. If you don't want 2x's in the front, use 1x or 5/4, or whatever. Add 2x4's around the top and bottom on the inside, make a base from 2x4's that are lap jointed at the corners, screw that onto the cabinet base, add your casters, attach your top of 3/4 or double 1/2 stuff (plywood, mdf, particle board) and you have a very strong box. And for our rocket science friends, I would ride that assembly to the moon.

As for the casters, spend some money here. Good quality, large diameter wheels will move easily and help reduce the tipping tendency by moving over small imperfections in the floor. You may want to have all four be double lockable casters (locks the wheels from moving over the floor and locks against spinning around) because you have a large "wheel" spinning at the top that will tend to add twist to your assembly. Add some weight to the bottom of the cabinet to help over come all that weight on top. You can do that with stuff in the bottom drawer. I have an old cabinet base that I use for my counter top drill press. I store light stuff on the shelves, but I put a 50 lb bag of sand on the bottom (because I had it) and it works great. Now you can spend time using your new machine.

Ray

[Larry Reimer]

Brian, sorry you had trouble at the APA site, it seems to work fine from this corner of the world. At the site you want to go to publications about plywood, then select the free downloadable .pdf file titled plywood design specifications. Registration on that site is free and immediate, no waiting for a confirmation email.

As Ray and others have said here the strength will come from the assembly. Plywood on edge will carry a considerable load. Your assembly makes sure the box stays together and the vertical pieces stay vertical.

[Norman Hitt]

The site that Ray brought to our attention has very good information. If you search on the site for their publications there's one for plywood design specifications. It's available for free download. Will tell you how much load plywood can handle when the sheet is put in compression on edge. There's also a bunch of other good info there.

Thanks for pointing that out, Larry. It's been quite a while since I visited that site, and I guess I just never got that far into the site. I'll check it out for my/our project.

[Robert Mickley]

I think your over thinking things here. Kitchen cabinets are extremely tough. Come on its a box and boxes are strong. Think about it for a minute. Look at all the things that get put in cardboard boxes and bet stacked on a pallet then stacked two and 3 high and the bottom carton doesn't crush. I would be more concered about the top than the sides.

As long as the corners don't fail your never going to crush those cabinets. If the corners concern you glue a 3/4 square in the corners. That alone will add a lot of strength.

[Brian Parker]

I've learned a bit about the load capacity of lumber and I'm going to keep some of those links handy for future project designs.

For this one after I got the sander and found how high I wanted to make the work surface of the sander. After accounting for caster height the total height of the void was 21". I just decided to take some old 4x4 scraps that were laying around and used those as 4 posts and lashed them together with some scrap 2x3's. The only money that it cost me was for the 4 locking casters which I already had purchased.

[Ray Bersch]

Yea, but it was a great exercise. Which is half the fun of it. Good job.

Ray