Plywood Thicknesses

Hey all, I had to do a design for a plywood cutout Wikihouse for someone today, and I had to go to Home Depot to measure the thickness of plywood. I've been meaning to take the time and really measure the true thickness of the different types of plywood they have there.

Today, I finally made that time. Below there is a link to an Evernote document with a picture of each piece of ply, it's thickness, overall size, and price.

I am going to get this into a speadsheet where we can all add to but for now I've got an Evernote document you can all see:

[www.evernote.com]

This should be really good for making designs that are fitted together.

If no one else is going to say it, thanx for this, not all inclusive and what each store has will vary but still a good ref.

You're very welcome! It's not all inclusive, and I suspect that some of these can change. I did this more just to get people aware that thicknesses matter when you're making things that fit together. I made the mistake a few times of assuming that the called thickness of a material was actually how thick it was, and I ended up with some furniture and other parts that didn't fit well together.

Most of the furniture you make from [www.opendesk.cc] requires you to use a specific thickness, or adjust the openings accordingly.

One suggestion is to create a test strip with a number of pockets of varying thicknesses, then try fit to the pockets over the edge of the plywood you are using to make sure everything will fit together the way you want it to.

Say the nominal thickness of your ply is .75". In a small section of the ply, create a rectangle that is 10" wide and 5" tall. Then draw a series of rectangles that are all 6" tall (extend beyond the original rectangle on both sides), and .71", .73", .75", .77" and .79" wide (width is in .02" increments on either side of the nominal width.) A big hurrah for anyone who responds with the reason why you make the pockets taller than the test strip.

Pocket each of the rectangles to a depth of .375" WITH THE BIT THAT YOU WILL BE USING to cut out your parts. There is enough of a difference in the way that an up spiral and a down spiral machines, and machining with a climb cut vs. a conventional cut that it will affect the size of your slots/pockets.

Cut out the rectangle, then make a notation of the width of the slots before you forget what you have done. Also write down the bit you used, and the cut direction (climb/conventional.) You could get fancy and use the ShopBot to mark the width, but a Sharpie works.

When you get a new sheet of plywood, fit the test strip over the edge before you create your design files. Remember that some times, you want a tight fit (going together once, never coming apart again), sometimes a looser fit (plan on breaking down the furniture for moving to a new location, applying paint after you cut out the parts but before assembly.)

Check out the 100kSchools.org website for a picture of the test strip we made in Japan (mm instead of inches, process the same.)

You have to extend it past so your rectangle piece of ply can fit into the slot.

This is a really smart idea, I am definitely going to try this out so I can check things before I embark on a huge project.

For the test piece, I should be using the same kind of ply to cut the test slots in as I am using to make the eventual piece right?

Well, if I'm reading the description correctly, all we need to do is to take a piece of the material and cut a series of dadoes (at the .375" depth) of the needed test widths, all the way across the test piece so that you can fit the test piece over the edge of the material to be used for the project in order to find the proper fit.

That's great Sally, I'll add it to my list of jigs and templates to make.