woodnthings

This topic came up in another thread, and I had forgotten that I had an easy solution for occasional cross cutting 4 x 8 panels. I made a guide for my circular saw that is 90 degrees square to the length by using the factory end of the plywood to set up the guide. It's close enough for my work! Two clamps keep the guide from shifting. Measure the distance from the saw blade to the saw base and add that dimension behind the cut line. In this case 1 1/2" clamp it up and saw away! bill

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Sleeper

Hey Bill, I could have used one of those about 10 years ago. I got a great deal on some ½” shop grade plywood. I didn’t have a use for it at the time, but when I finally started to cut it up, I found out why they were so cheap. They were exactly 4’ wide and each side 8’ long, but they were completely out of square. My buddy and I both bought 10 sheets each and they were all cut the same way. I had to go out and buy another sheet of good plywood to use as a square.

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woodnthings

To check a square for "square" draw a line across the plywood using the edge to be checked. Flip the square to the other side of the plywood and draw another line close to the first and see if they are parallel. If not, it's one of two things: the edges of the plywood aren't parallel (not likely) or the square is not "square". Adjust the square to 1/2 the distance "off" and try again. Generally speaking aside from bargain sheets, the plywood is close enough to square for the jobs I do. A drywall square can also be used as a reference since it's got a 48" long leg.
I also use a ball point pen when doing layouts since it makes a fine, but dark line for accuracy. bill

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Never stand directly in front of a horse or tablesaw that's running!
If you're not making dust, you're gathering it. After I reread my own posts, I agree with myself even more.

skymaster

Wood: If you were to make the 4' cross pc a few inches wider, put a strait pc of hardwood on it and rip the pc with your saw than you would have a guide that is EXACTLY on your cutline. just make your marks, clamp it as you do right now and cut no measuring at all
Great jig idea tho. I got tired of em and bought a slider attachment for my saw :}. I just ruff rip em then finish on TS. It is a few extra mins and cuts but soooooooo much better and easier for me.

woodnthings

I'm leaving now to make it that way. Thanks

__________________
Never stand directly in front of a horse or tablesaw that's running!
If you're not making dust, you're gathering it. After I reread my own posts, I agree with myself even more.

lvjake7761

be aware also 4x8's dont always come square
measure the sheet corner to corner they if they match its square

Jordy3738

That's a nice jig. We've used the same concept when squaring up cabinet stock rips, with a router and 1/2" straight cutter, prior to cross cutting on the table saw.

Never had enough money to invest in a sliding table saw.

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Julian the woodnut

Nice straightedge/square there! I think skymaster has the solution to make this a must for everybody to have one of these. The zero clearance square with no math involved. I must build one now....

pianoman

I see there was no mention of using the proper blade...I mean, cross cutting a 4x8 ply panel tends to chip out the top side when using a circular saw. The cross cut jig is nice...but setting up a jig using a 4x8 sheet is just wrong. Most every sheet I`ve found has one end out of square. Still, nice jig. When I cross-cut a panel...I use a Bosch jig saw after scribing a line with a knife...then block plane to square. A slight negative hook blade works well for cross cutting ( less chiping). Of corse, using a radial arm will chip out the bottom side unless you have the right blade. Today, you can buy down cutting blades for a jig saw...and some even have a boot insert to minamize chipping. Note, when using a down cutting blade in a jig saw...set the cam ation to O. Also, the down cutting blade was designed for cutting counter tops. Rick

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Julian the woodnut

Pianoman, I'll take a good circular saw with a decent blade over a jigsaw anyday. The time spent scoring, then cutting then cleaning up with a plane would take too long for my taste. I prefer to tape the edge, then use a straightedge with a zero clearance edge. I get no tearout, and don't need to clean up the edge with a plane, which would dull the plane quickly anyways. Less steps, and a clean edge wins in my book.

woodnthings

Just cut "bad side up." or use tape as suggested.
Square is relative. This jig cost about $5 and is not as accurate as a $15,000 sliding table saw, but close enough for my purposes. See post above for squaring and adjusting a square. How do you check a 4 x 8 sheet end for square if you don't have a good square other than a diagonal measurement? Lets say the diagonal measurements are different....which end is out of square? I suppose the 3, 4, 5 triangle is OK, but we just measured and marked 3 times with a tape measure... accurate? bill

__________________
Never stand directly in front of a horse or tablesaw that's running!
If you're not making dust, you're gathering it. After I reread my own posts, I agree with myself even more.

skymaster

Square is RELATIVE. Lets say that the Jig is square and you referance off the top factory edge, and crosscut the sheet. Well you now have two edges that are SQUARE to each other and can now be used to square the remainder. As far as blade I use a Freud 60 tooth fine blade and it rips fantastic and crosscuts the same, no problems. Always cut good face away from the saw and with the Jig you will have a virtually chip free cut.