Perfect Cuts With a Circular Saw Guide





Introduction: Perfect Cuts With a Circular Saw Guide

About: Build instead of buy....most of the time.

While a nice table saw setup is beneficial for perfectly straight cuts on sheet goods it's not 100% necessary. You can get perfectly straight cuts with a cheap circular saw and a guide track. One of the advantages of using a circular saw and a guide track over using a table saw is most often it's much easier to move the lightweight circular saw over the plywood rather than move the heavier plywood over the table saw.

This isn't an original design or concept as people have been doing this for years. You will need the following tools:

  • Circular saw.
  • A few clamps
  • Sawhorses will help. If you don't have sawhorses a few scrap boards laying on the ground to elevate the plywood will be fine.

You will need the following materials:

  • Either 5/8" brad nails (what I used) or 3/4" screws.
  • Wood glue.
  • One sheet of 1/2" plywood. You won't need a full sheet but you need the full 8' length.

Using power tools incorrectly can result in a very bad experience. I used my brother's circular saw that had the guard tied back. Don't do that. It's dangerous. You can walk with a wooden leg and hold things with a wooden hand but you can't see with a wooden eye. Wear your safety glasses.

Step 1: Cut the Fence Piece

First, make sure the plywood you are using has at least one perfectly straight factory edge. As long as it looks straight when looking down the full 8' edge it should be straight enough to use. Keep track of which edge is the factory edge during this build as that's the edge that will be the fence for the circular saw to run against. Use sawhorses or boards on the ground to work off of with the plywood. (pic 1)

With the plywood on the sawhorses the first thing I did was rip a small piece off of the long direction. I believe this was a 3” wide piece. Its good to cut as straight as you can but not absolutely critical. (pic 2)

The main thing to keep track of here is the factory edge of the plywood. It's the right edge that I'm pointing to (pic 3).

Step 2: Cut the Base

Because the factory edge is straight it is the most important part of this track build. But it's only half of the circular saw guide and we still need a base for the saw to ride on. I used the factory edge as a guide clamped to the rest of the plywood to cut off another strip. This time it was about 9” or so wide. I clamped it down on both sides. (pic 1)

With the first strip clamped down and ready to be used as a reference fence for the circular saw I noticed there was quite a bit of flex as I pushed on it in the middle of the panel. To stop this flex I clamped a scrap piece of wood in the center of the plywood resting against the opposite side of the first strip. This stopped the first strip from flexing. (pic 2)

Then with the saw tracking against the factory edge of the first strip I cut the 9” wide base strip. (pic 3)

Step 3: Assembly

This is where measurements might be a little different from saw to saw. You may have to adjust your dimensions as needed. With the saw blade resting against an edge of the plywood I used a tape measure to determine that the distance from the furthest edge of the circular saw base plate to the blade was 3-3/4”. As I just said, this measurement will probably be different on different saws as there is no standard here. (pic 1)

The first strip with the factory edge will be glued and nailed to the wider base strip but the factory edge needs to be just a little further from one edge of the base strip than the distance from the blade of the circular saw to the furthest edge of the saw base plate. So in this case I got it close to 4” on both sides and marked my base strip. (pic 2)

After adding glue to the smaller strip I nailed it to the base strip making sure it is on the reference lines from the previous step. This is where you can use screws if you want. Really, the glue is where the holding power comes from. The nails or screws are just to hold the pieces together while the glue dries. (pic 3)

Step 4: Make It Zero Clearance

The precision of this jig comes from this step. Once the smaller strip is secured and the glue has had time to cure a cut is made with the circular saw referencing against the factory edge of the smaller strip. This establishes a zero clearance line for where the circular saw will cut every time you use the track.

Step 5: Enjoy Perfectly Straight Cuts

We now know that the outside edge of the base strip is exactly where the circular saw will cut when slid across this track. To use it simply line up the edge of the track with reference marks on your material, clamp it down, and cut a perfect line every time. Remember that the circular saw blade itself will remove a little bit of material as well so it's best to place the track on top of the material you are cutting to length and not the off-cut of your material. (pic 1)

Having an 8' track like this is incredibly handy for cutting down sheet goods. But it can be a bit cumbersome at times if you need to make precision cuts on smaller pieces like a 3' x 3' sheet. For that reason I made a second 8' track and cut it into 5' and 3' sections. (pic 2)

Remember that Lowes and Home Depot will make a few cuts for you on plywood so if you buy your plywood from them you could have them make a 3" cut first followed by a 9" cut along the long direction and then just go home and put it together :)

If you've enjoyed this Instructable and want to see more stuff like it check out my website at I've been posting projects weekly since early 2013 and have a ton of stuff to browse through :) Have a great day folks.

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For making that first cut parallel on both sides (as gnach mentions below) clamp a straight, narrow piece of pine about 12" long to the bottom of the shoe so that it will keep the blade a consistent distance from the factory edge. You'll have to be on top of the plywood for this cut, so it's best not to use saw horses, but just support it above the ground with some 2x4s.

The framing crews I worked on would use a small wooden wedge to hold back the blade guard (placed inside the blade-guard lever). It's easily removed, so that the blade can be guarded when the saw is put away or is bouncing around in the back of the truck. And as you mentioned, this is not a recommended technique for the inexperienced. It's not enough to try to remember that the blade is exposed. You have to intuitively and habitually conceive a saw with a pinned-back blade guard as a fast-moving weapon of pain and death, so that even when you're tired or distracted, your instinct can keep you safe rather than relying on conscious memory. I once saw a guy with a grizzly flap-wound scar on his thigh that was the result of his holding his saw too close to his side, and the blade caught on the handle of his hammer that was hanging from his framing apron. That jerked the saw into a rotation, right into his thigh, and from the looks of things, it penetrated as far as it could go. Another danger is putting the saw down on the floor before the blade has stopped spinning, where it becomes a one-wheeled clockwise-rotating go-cart that heads right for your toes. Pinning back the blade guard is useful for some precision cuts, because it makes a smooth entry into the wood easier, but use the wedge, and remove it as soon as the cut is done. The snap-tie method is both less safe and more likely to lead to a dull blade.

2 replies

Bo88y, it's never okay to wedge or tie your guard open on a circular saw. There's no reason to either. Circular saws are designed to be used 2 handed, the left hand can hold the guard open safely via the lever and it springs back over the blade as soon as you release it.
I've met a guy who will never squat his own body weight again because he severed his quad with a circular saw. It's just not worth the convenience. If you need 1 hand on the job while you are sawing then you are taking a short cut. Stop, use a clamp or a guide and do it properly!
Great guide Jay, it's nice how the saw 'foot' doesn't come in contact with the material, mine often leaves rust marks behind coz my saws old and cheap.

Another way to keep the foot from marking up the material is to occasionally run a file over it to take down any "pimples" that may have been pushed up by nicking or rust. Then, a couple of 2-layer strips of masking tape running lengthwise over the foot will hold it up a smidgen above the work. Wrap the ends of the tape up over the top, to avoid snagging.

Most of what I said about the wedge was a warning of what could go wrong, and advice not to use it if inexperienced. But there are reasons that professionals use it, and there are reasons for blade guards' having little handles on them, so that even without the wedge, one can manually hold the blade guard retracted while cutting. Some blade guards will not retract properly on certain thicknesses of material, but will act as a hook that prevents the saw from being pushed forward. Some saws will tend to twist to the right when starting a cut, because beginning the blade-guard retraction exerts a drag to the right side of the handle. The quality of the work can be affected.

The best safety device is an attentive, focused tool-user.

greta job

thanks for sharing

If you put the saw against the guard on the other side(motor opposite), you will be pushing AGAINST the guide instead of away from it, so the saw will not tend to drift away. Also, on(most? all?) circular saws, that measurement is 1.5 inches.

With this method, you can use C-clamps to hold the guide down instead of nailing it. (and not worry about the saw motor bumping into the clamps)

You're a great brother!

Fantastic! Thanks for submitting this. just in time for me as I was conteplating on how to best rip a large sheet of plywood i have.

1 reply

Awesome. Glad you are able to find use in this. Have fun!

That is a great idea!!! Thanks for sharing it :)

I have always problems with those kind of cuts because it is impossible to make a perfect one.

My circular saw has a rule that helps you to make some kind of perfec cuts on the edges but depends on the bad or good is the edge (

Thanks very much for this. What a brilliant idea.

Good instructions; but I would add one consideration since I had to remake mine a couple years ago.

When you make that second cut to generate the base, be sure it is wide enough to allow clamping beyond the saw motor. Otherwise, you can't make a full cut without adjustments.

Good job on the jig! Maybe over-stating the obvious but make sure the height of the jig is less than the clearance of the saw motor, before nailing/gluing the pieces together. Some circular saws have very little clearance on that side.

I really appreciate the simplicity of the technique to insure perfection in a long cut, i think i will adapt it to a router for making exact duplicates of complex shapes like the rib for a wing, certainly i'm building one for my circular saw!

Great instructional! I have been doing this with clamps for years. I guess I can just make a long and short one. Thanks for sharing!

Excellent set up, being a Festool track saw owner I can say that track saws are great for tons of uses.
The only threat is that of running your saw off the track away from the guide side, hardly a big problem if you are paying attention.
I would consider using non slip tape on the bottom to keep the guide in place if not using clamps.

Great idea and instructable. Made a set today for my plunge saw, thanks for sharing.

This is great! I can't afford a table saw and have been forced to use a router with a templating bit to get my plywood rips square post cut. Didn't quite know how to make a jig but thought of it several times...then I stumble upon this great instructable! Thanks! I'm headed out to my backyard shop right now.

I wish I saw this a week ago, definitely using for the future

Very nice! This will be my next project.