How to get "Square" Cuts with Circular Saw Guides?

[Andy Sowers]

Hi

I'm wondering how folks ensure that they get square cuts when using circular saw guides?

Last fall, I bought an Ez-Smart guide with the speed square, but I find that my cuts are off by as much as 1/16" when cutting larger sized panels (on say ~4'x4' panel). I'm sure the problem has to do with:

1) the fact that the square itself may not be square enough
2) the length of the square might not be long enough compared to the length of the cuts (the square is 1.5' in length).

For issue #1, the manufacterer has a procedure to square up guide using a rafter's square, but I question whether I could find a rafter's square that's accurate enough to fix the problem. I have some accurate engineers squares, but they're certainly way too small to be used in this application. But even if I could somehow get the square perfectly squared up, I still dont think this addresses issue #2...

So I open this up to you guys who use saw guides (be it EZ, festool, Dewalt, etc.), how do you get square cuts?

Thanks

Andy

[keith ouellette]

I'm not familiar with your set up but I use a bar clamp to cross cut plywood.
here is the one I have.

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/clampinx.html

If the plywood is bowed a little then I clamp the the bar down with some small clamps so that it will sit on the plywood and not let the saw slide beneith the clamp.
This will only get you a square cut if the plywood is exactly square to begin with which may be your problem also.

with careful measuring and placement of the bar clamp you can make a cut parallel to the lead edge.

I don't know what type of plywood you are cutting but it may not be square to begin with and this will mean you will not have a square piece when your done.

If you are using a guide to rip a piece of plywood you will have the same problem.

[Ken Fitzgerald]

Andy...using a framing square as a reference is great and if they are not perfectly square, they can be adjusted to be that way. Most good framing squares come with a small manual and tell how to make those adjustments. It involves "peening" the square with a punch and hammer to move it into being perfectly square.

[Paul Steiner]

When it comes to square cuts on sheet goods,
I use a framing square and a drywall t-square to check for square. This is accurate enough for most things generally after one cut with the circular saw the piece is small enough for my tablesaw.

Another factor to getting a good square cut with a circular saw is blade thickness and quality. All of the blades found at borgs are now made of thin metal about 1/32" with large carbide teeth about 1/8". These blades flex to easily. Any movement on the top of the saw will cause the blade to flex and throw off your cut.
I use blades that are about 1/8" thick with 3/16" teeth, no flex. You can still order these or find older ones. I have one from 1980 cuts as straight as an arrow.

[Colin Giersberg]

I have used the Pinnacle 24" T-Square for this purpose. I don't know how accurate this is, but so far I haven't been disapointed.

Regards, Colin

[Michael Prisbylla]

I use a drywall t-square, too. Works well. You can also use a 3-4-5 triangle measurement to check for square.

[Walter Savick]

I saw this in a magazine from a guy in Piqua Oh. Sorry, I don't remember the magazine or the guy's name. You need a square that reaches at least half way across your panel. It doesn't matter if your square is not square. It will still work. This assumes that your panel has parallel sides.

Mark your panel on one edge where you want to cut it. Find and mark the center of the width of your panel where the cut line should be. With the square aligned with the edge mark you made earlier, mark an intersecting point on the center mark you made.

Flip the square like a book page to the other edge of the panel. Align the square with the intersecting marks at the center of the panel and mark the edge of the panel opposite from your original length mark.

Align your cutting guide with the marks on each edge and cut. Disregard the center marks for this step. Your cut line should be square with the sides if they are parallel.

Hope I explained this OK:rolleyes:

[Doug Hobkirk]

My humble suggestions:
1) Tune your framing square to make it spot on using the peening technique.
2) Adjust your EZ Square per Dino's instructions.
3) Accept that you should make a mark at the far end of the cut to guarantee good results if you are cutting more than 24".
OR
Spend money and build a power bench and then dial it in carefully!

(I also use the EZ guide system)

[Matthew Hills]

I've gotten in to trouble with guides if I try to rush anything.
Be careful and double-check your measurements and alignment after everything is clamped down, and use things like offset blocks to account for the base width of your circular saw.

Note that if you're doing cuts in the middle of a sheet, you can use a compass and straight edge to construct the perpendicular line. (e.g., http://www.mathsrevision.net/gcse/pages.php?page=49 ). This technique requires enough edge on both sides of the desired cuts that you can extend your marks out across the wood.

[Burt Waddell]

Hi

I'm wondering how folks ensure that they get square cuts when using circular saw guides?

Last fall, I bought an Ez-Smart guide with the speed square, but I find that my cuts are off by as much as 1/16" when cutting larger sized panels (on say ~4'x4' panel). I'm sure the problem has to do with:

1) the fact that the square itself may not be square enough
2) the length of the square might not be long enough compared to the length of the cuts (the square is 1.5' in length).

For issue #1, the manufacterer has a procedure to square up guide using a rafter's square, but I question whether I could find a rafter's square that's accurate enough to fix the problem. I have some accurate engineers squares, but they're certainly way too small to be used in this application. But even if I could somehow get the square perfectly squared up, I still dont think this addresses issue #2...

So I open this up to you guys who use saw guides (be it EZ, festool, Dewalt, etc.), how do you get square cuts?

Thanks

Andy

Andy,

Secret number one is to make sure the line you are setting the square on is a good, smooth line. The factory edge of a sheet of plywood is typically rough enough to throw a square off. Secret number two is make sure the square is set up as perfectly as possible. A perfect square on a perfect line should yield a perfect cut. If I recall correctly the EZ Square is 16" long and you are typically doing a 48 1/2" cross cut. That means any error along the edge of the square will be multiplied by three when you make a cut. Secret number three is make sure the square doesn't move during the cut. If I am doing a cut that must be perfect, I clamp the out-bound end of the square.

Also as someone stated, the PBB is a highly accurate approach to cutting and routing wood.

I now use the EZ system for all of my cutting except some of the miter cuts. I find results to be equal to or better than those using unisaws and an excaliber sliding table.

Burt

[Jamie Buxton]

Here's a thread about how I deal with that issue.

http://www.sawmillcreek.org/showthread.php?t=49778&highlight=guided

[Jim Heffner]

Andy, I read all the posts about checking this and that and types of methods...all good ideas and advice that I read....but I didn't see anything about relating to the saw. I would first start with the saw, check to see if it is square with the sole plate (base) and then the blade, to see if it is running true with base. A friend gave me a Milwaukee circular saw that he said would not cut straight...after a few minutes
of checking it I found the problem. It had been dropped and banged around and generally abused to the point that it couldn't cut square if it had too! I took the time and effort to remove, the sole plate and fix the problem re-align it, and now it works like new! I'm not saying this is your problem...but it is another thing to think about and check it out. Hope this
helps you find the problem........

[Chip Lindley]

A square SQUARE is *square*! An unsquare SQUARE is *not square*! Test your square to insure an exact 90degree angle. I use a Starrett drywall square to mark out sheet stock. I tweaked the square with a longer *T* and set it to an exact 90. It works great to mark out sheetgoods, and then apply a ripping guide made specifically for my SkilSaw.