Question on truing up plywood

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Forum topic by Steve posted 12-09-2017 06:49 PM 969 views 0 times favorited 10 replies Add to Favorites Watch
View Steve's profile


2079 posts in 1354 days

12-09-2017 06:49 PM

Wife sent me this table to build for the kids So I planned it out to get all the pieces I needed out of a sheet of plywood. With the understanding that the sheet isn’t exactly 4’ wide, but overall it shouldn’t matter too much.

Perhaps I was hoping for too much out of that stock piece of plywood. But I was hoping to get 2 equal sides after having the sheet ripped in half, but that didn’t happen. One side is about 1/8” wider than the other.
And then I wanted a 2×4 piece out of one side. But it seems somewhere along the way, the saw wasn’t at 90, so that cut wasn’t square, so i’m left with having to true up the larger piece myself.

So to get the 2’ x 4’ piece trued up, I’m assuming I should i put the cut side against the fence? Then I’ll have two parallel sides that I can then true up the edges with?

This is probably a novice question, but I thought I would ask the experts.

Here’s the table I want to build and what I was hoping my cut list would be.

10 replies so far

View jerryminer's profile


960 posts in 2213 days

#1 posted 12-09-2017 07:27 PM

I think you’re on the right track. Whichever edge is straight can be used as a reference against the fence. Cross-cutting your panel first will give you a panel that is easier to handle.

A small loss of width will not matter a bit in this project (will anyone know the difference if the table is only 23 1/2” wide instead of 24”?)

-- Jerry, making sawdust professionally since 1976

View Steve's profile


2079 posts in 1354 days

#2 posted 12-10-2017 12:33 AM

Thanks for the confirmation. Not the end of the world I know. But I was hopefully optimistic that I could just make a few rips and then be all set for assembly.

View KenKorch's profile


14 posts in 940 days

#3 posted 12-10-2017 01:00 AM

Many folks warn that factory edges of plywood may not be truly straight. With that in mind, if you run the plywood factory edge along the table saw’s fence, then the cut will be parallel to the factor edge, but it is possible neither the factory edge nor the cut edge will be straight from front to back.

This is one place where the use of a long track saw can really help. It can be used to cut a truly straight edge (cutting just a little bit of material off) that can then be placed against the table saw fence, and in turn produce a truly straight cut edge.

The best of luck and joy on your project!

View Shamb3's profile


41 posts in 953 days

#4 posted 12-10-2017 01:16 AM

If you have a big enough cross cut sled you can get the ends back to square real easily after you get the long sides parallel.

View sawdustdad's profile


379 posts in 1657 days

#5 posted 12-10-2017 03:25 AM

I always use a factory edge against the rip fence. Have never really had an issue. Cross cuts up to about 20 inches can be handled on the sled. Wider than that, and it’s back to the rip fence.

You just need to make allowance for the blade kerf in your plans. I usually allow for a tad more, maybe assume two pieces 23-3/4 out of a 48 inch panel. This allows me to run the first cut panels through the saw a second time to clean up the factory edges.

-- Murphy's Carpentry Corollary #3: Half of all boards cut to a specific length will be too short.

View JBrow's profile


1368 posts in 1692 days

#6 posted 12-10-2017 03:33 AM


Echoing sawdustdad, the cut diagram for a sheet of plywood that measures 48” x 96” will not yield all the parts shown in the cut diagram at the specified dimensions. Each time the plywood is cut, the kerf of the blade will produce waste that is unaccounted for in the cut diagram. It is the waste produced by saw kerf during the first cut that may explain why the first two pieces were not equal in width. A table saw fence set to 24” would produce an off-cut that is 23-7/8” wide.

Since the cut diagram fails to account for the saw kerf, a 24” wide piece of plywood cannot yield all the specified parts. At best, the width of the bookshelf parts can be no wider than 11-15/16”. The problem of yielding aprons, bottom, and cleats from the top offcut is more acute since several cuts are required; each cut producing 1/8” of waste (assuming a saw kerf of 1/8”).

View Steve's profile


2079 posts in 1354 days

#7 posted 12-14-2017 09:05 PM

we’re getting there. just need to sand it up and then decide on a finish. couple spots that stick out to me like when the wood moved while screwing a pocket screw, buy my daughter insists that I’m the best at building things out of wood. and that’s all matters. :)

I’ve found that i could definitely benefit from a zci and need to get on that. and a mobile base is also a high priority. i did have fun building this though and want to do more projects to build up my confidence using the table saw.

View jerryminer's profile


960 posts in 2213 days

#8 posted 12-14-2017 10:06 PM

Looks good. And the client is happy—that’s the main thing!

Every new project is a learning experience. You’re well on your way. Best of luck.

p.s. ZCI is very helpful. Also, a “scoring cut” will help keep your cuts clean—- Set the blade very shallow, like 1/8”, make a pass, then cut again at “through height”—almost like having a scoring saw.

-- Jerry, making sawdust professionally since 1976

View Steve's profile


2079 posts in 1354 days

#9 posted 12-14-2017 10:12 PM

thanks for the tips. it’ll be nice to park my car back in the garage once i get the courage to move my table saw out of the way. i’m not sure what craftsman was thinking with those factory wheels.

View Andybb's profile


2762 posts in 1376 days

#10 posted 12-15-2017 01:23 AM

Looks like you nailed it! Nice work.

-- Andy - Seattle USA

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