Intro: Perfect Cuts With a Circular Saw Guide
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 jayscustomcreations.com. I've been posting projects weekly since early 2013 and have a ton of stuff to browse through :) Have a great day folks.