I wanted to get more from my circular saw. I developed and made this portable saw guide based on some 3/4 inch plywood and two very straight pieces of 1 inch angle iron. It can make both crosscuts and rip cuts, if one of the angle iron rails is moved away from the other.
This saw guide requires a half-sheet square of 3/4 inch plywood (4 feet x 4 feet).
Step 1: View From the Front
The blade guard has been tied in the retracted position with a piece of wire. You see a slightly tapered piece of 1 x 2 holding the switch trigger in the "on" position. This is not necessary, or even desirable, for crosscuts; but it is necessary for rip cuts.
I added a strut to keep the weight of the saw motor from causing the base to flex. I described this in another Instructable titled "Too Much Flex in a Circular Saw Base."
Step 2: The First Step
The first step is to begin cutting 3 inches from one of the machine cut edges of your plywood. This piece will be 3 inches wide and 4 feet long. Cut as straight as possible, even though you may be guiding the saw freehand. Once you have this piece cut, you can mark the factory edge and use it as a saw guide for cutting another just like it. Glue these one on top of the other to make the front fence for the saw guide. Keep the edges aligned and square as shown in the photo. Glue and clamp the fence to the saw guide table.
Cut another piece from the plywood that is almost 3 inches wide and 4 feet long. You want the remaining large piece to be 3 feet by 4 feet because the steel angle iron rails are 3 feet long. You will use this last narrow piece to make the rear support for the angle iron rails. Cut two pieces from it about 12 inches long each. Glue them together. I also glued two short pieces from this together to make a block 3 x 3 about 10 inches long. I fastened this block below the saw guide table so I could mount the saw guide on my Black & Decker Workmate as well as on saw horses.
Step 3: Drill Holes for the Rails
Purchase two 1 inch angle iron pieces 3 feet long each. Sort through those available to find two that are not bowed in any way, but are very straight.
Here is one of two screwheads holding the angle iron rails in place. They are 1/4 x 20 inch bevel head screws. In the photo you can see a bit of the support for the rear ends of the angle iron rails. Do not glue the rear support to the saw guide table. It will remain adjustable for assuring square cuts from the saw guide. Two similar screws anchor the rails at the front, too. Carefully mark holes to drill for the 1/4 inch screws. Drill the holes as straight up and down as possible.
Step 4: Tee Nuts
The nuts that receive the 1/4 inch screws are Tee nuts. They can be recessed so the surface remains flush and on the same plane. This keeps them out of the way of several things. That will be very necessary on the rear support for the angle iron rails. The Tee nuts will be buried below the support, but above the surface of the table. This is so the rails can be anchored to the rear support, but the rear support still has a little lateral movement to assure a square cut.
Step 5: Two More Holes for Rip Cuts
You will need to make another hole in the front fence and one in the rear support so one of the angle iron rails can be moved out away from the other and be anchored. This becomes the rip cut position for the rails.
I also made four 1/4 inch spacers from Masonite. They go above the rail supports and below the rails. They provide just a little more clearance for sawing 2 inch stock. Longer screws for mounting the rails are necessary when these spacers are in use.
Step 6: Adjustment for the Rails
This is the photo of the rear support holding the angle iron rails in place. Notice the two Tee nuts for screws. They come up from the bottom of the saw guide's table. The holes in the table are elongated so the rear support can be moved side to side 1/8 to 1/4 inch. This is for fine adjustment to insure that the rails are square to the fence and the cut will be square. Notice also that the Tee nuts and screws are well out of the way of the blade's path.
About the time I first made this saw guide a friend was making a butler's table for his wife. He used solid black walnut. He had only a Shopsmith table saw for his saw. Rightly so, he was concerned about getting the top of his butler's table square. I told him about my saw guide. The guide's table was more than large enough for his table top. We held our breath and made the cuts. Then he measured diagonally between opposite corners to check for square. The difference between the two measurements was less than 1/16 of an inch. He was satisfied. I was pleased.
Step 7: Measure to Avoid Blade Heeling
The saw has some movement in the rails and is not automatically aligned. Measure the distance between the leading edge of the blade and the fence when ripping. Make it the same for the trailing edge of the blade. The markings on the rulers are a little easier to see with the eye than with the camera.
Step 8: Locking Down the Saw for a Rip Cut
I needed some way to hold the saw firmly in place while ripping. I drilled two holes at the back of the saw base and two holes at the front. Then I cut pieces of 1 x 2 and drilled them for dowels so the dowels would fit into the holes I had drilled in the saw base. One piece was made to fit the front of the saw base and one the rear. The face of the 1 x 2 rested against the vertical edge of the angle iron rail. A very small C clamp applied pressure to hold the 1 x 2 in place against the angle iron, which held the saw down, too. I would have included a photo, but the original pieces have been lost in two household moves.
Step 9: Something to Make Life Easier
A friend cut a square of 3/16 inch steel plate for me. I had access to his oxy-acetylene cutting torch at the time and made an opening for the blade. I drilled some holes in the steel plate to correspond with existing holes in the saw base. The holes were countersunk on the bottom of the plate for bevel head screws.
A plate like this allows changing from a rip cut to a crosscut without moving one of the angle iron rails to its other location.
By clamping pieces of wood to function as straightedges or fences to the work surface of the guide table and placing them at any desired angle, it is possible to cut accurate mitered corners with this saw guide. Such straightedges would need to be almost 3 feet long. Their front ends could be placed against the fence to make them more firm.
Whether using the steel plate to mount the saw or just using the saw's own base on the angle iron rails, the saw moves more smoothly if I put just a little used motor oil on the rails.
Take a look at the two other photos to see the saw mounted on the plate in both the rip and crosscut positions.
Step 10: So, What Will It Do?
With this circular saw and saw guide I made two nightstands for our bedroom. The plan was to use a painted finish, so I was able to use wood I found on someone's curb waiting for the garbage truck. The moulded edges were done with moulding head cutter mounted on another machine. We have used these nightstands almost 30 years now.
Step 11: Bonus
I drilled holes near the end of each angle iron rail to match the holes I drilled in the saw base as mentioned in Step 8. I can remove the angle iron rails from the saw guide table and attach them with bevel head screws to the saw base. I can use C clamps to attach a straight edge guide for ripping panels greater than 24 inches. Measure from the front and back edges of the blade to make sure the guide is parallel to the blade.