Cut Off Guide for a Circular Saw





Introduction: Cut Off Guide for a Circular Saw

About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first ...

Sometimes following a pencil line with a circular saw does not give the straight, smooth cut you want. For times such as those, a cut off guide is a great help. I was looking for a welding project and had some left over steel from another project. I decided to make my own saw guide.

The slotted brace on this circular saw is described in another Instructable I did. It makes home duty saws more accurate.

Step 1: Materials

I used some 1/8 x 3/4 inch flat bar and some 1/2 inch angle iron.

Step 2: Overview

This is an overview of the cut off guide.

I wanted it to have a low profile so it would not interfere with the saw motor, and yet I wanted to be able to hold it firmly against the front edge of the board I am cutting, as well as be able to clamp it to the board, if need be, without the clamps getting in the way of the saw motor.

Step 3: First Weld

The first weld is a butt weld at the end of the guide nearer to yourself when in use. I ground the weld to be flush with the surface of the flat bar.

Step 4: The Second Weld

The second weld attaches the angle iron to the brace piece. See the photo in step 3. A tack weld or two will do. But, before making the weld, try to make the angle iron exactly perpendicular to the long guide that goes against the saw base. Use a good square. See my Instructable on making a square to be truly square.

Step 5: The Third Weld

The third weld attaches the long guide piece to the angle iron. I made a light tack weld and also used a plug weld. A plug weld is made when the welding rod is pushed down into the steel at a considerably higher than normal amperage, melting a hole as you go. Then you back the electrode out of the hole, filling it as you go. The tack weld is on the side of the guide piece opposite the side against which the saw base rides (left side of the bar as shown).

Step 6: What I Would Do Differently Next Time

I was too eager to weld something. Welding makes metal very hot, and when it cools, it changes its shape. When I finished there was some distortion in the angle iron piece and in the long guide piece. I had to do some work with a file to make these straight and square again. See the yellow and red lines for the areas I had to dress with a file.

I would have saved some time if I had drilled holes and tapped threads for screws. I might have been successful with the welds if I had done only a little light tack welding, but the plug weld made just too much heat. The saw guide works well now and it is very strong, but I spent more time than I would care to admit making corrections with a file. Still, it is a useful addition to my tools.



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    15 Discussions

    Thanks. This saw never fit my hand well. I gave it to someone whose saw died, and I replaced it with a nice Porter-Cable saw I really like.

    Please do try it. You will like it. Since publishing this Instructable, I have made a second one for my son. It is held together with screws. There were no problems with metal distorting due to heat from the welding. Also, I used the guide in the photos again today. It still works great.

    What is alot easier is to just use a speed square (a plastic one is about $3.00) with an attached piece of 1" x 2" x 12" long (or even longer if you want) with a threaded bolt through it and knob on the other side. You can slide the piece of wood up to the circular saw blade and then tighten down the knob to set the spacing. The wood is easily replaceable if you change saw blades or even saws. Too, you don't have the risk of cutting into metal with the circular saw. This is really similar to the Kreg "Square Cut" jig - but the plastic piece they use to set to the circular saw would be the 1" x 2" replaceable piece of wood.

    3 replies

    I wanted something with sides on it longer than the common 6 inch speed square and did not want to spend for a larger speed square. I had one made of orange plastic, but it shattered the first time I dropped it (accidentally). Adding a piece of stable wood for a longer guide would work. I had not seen the Kreg Square Cut jig, but found a video demonstrating it. But, I have a welder and had been thinking about something like this as a useful welding project for some time.

    I understand. Certainly your steel cross-cut guide would be strong - take the hard knocks of being used in the workshop or job site. I used a plastic 12 inch speed square and attached a piece of plywood to it for my cutting guide. It enables me to switch between my two circular saws very easily. It hasn't broken yet - but I'm counting the days! Using the piece of plywood allows my to set it directly/exactly to the line of where I'm cutting (or at least suppose to be cutting). I can even trim a little of it off to be exact. I could have used a steel speed square for durability. But your right - they cost about $15. I actually got the idea from watching the Kreg Square Cut Jig but didn't want to spend the money for it. Too, Bench Dog makes something similar. In reality, I think my idea is better than either of the Kreg or Bench Dog Pro Cut Circular Saw Guide because I can also set it to do 45's or whatever. I do have to take it apart to do such though and switch the bolt around. But theirs won't do that. Additionally, if I do that - I usually have to replace the piece of wood that I used to show the cut line. Too, I found that the only Speed Square that works well is the Swanson Speed Square because they have the "slots" built within to place your bolt to attach the piece of wood. Anyway, I liked your idea.

    Some type of cut off guide is almost necessary for a circular saw. I struggled for years with folloiwing the line or positioning and clamping a framing square to the work. Somewhere I saw something similar to what I eventually made and coveted it. Whatever a person uses, it must be low enough not to catch on the saw's motor housing and be easy enough to hold firmly so it does not move. I like the idea of something the saw cuts the first time to provide positioning guide. Thank you for your comments.

    I made one out of wood strips and coarse threaded sheet rock screws. I used the old 3-4-5 trick (6 inches by 8 by 10 , actually) to make it square.

    Otherwise the tool is exactly the same.

    I agree with you, if I were to make it out of angle iron, I'd likely clamp, drill, and then screw in a sheet metal screw. Then I'd test for squareness, and then I'd maybe practice my welding and then grind the excess screw off.

    1 reply

    I recently made another of these for my son.  I drilled and tapped for machine screws.  It worked well.  Welding can make steel distort in funny ways.  What was straight becomes curved.  I used the 3-4-5 process to make a copy of a combination square and level used by the Egyptians thousands of years ago.   Thank you for the comment.

    Do you have any experience with JB Weld (an epoxy especially for metals).  I wonder how that would hold up for this application.

    1 reply

    I have friends who have successfully used JB Weld to restore stripped threads inside a hole and to repair a broken aluminum casting.  I think it might work.  I would rough up the surface on both pieces in the contact area with a very coarse grinding wheel for the best adhesion.   I would not want to drop or jar it, lest a joint break.  The same is true of plastic speed squares.  I had one of those shatter when I dropped it from a table top to the floor.

    I did recently make one of these for my son.  I used #8 screws and tapped threads in the receiving member.  That did work very well.

    That works. Often I have found myself wanting to cut a board greater than six inches, which is the size of a smaller speed square. A larger speed square runs $15 or more, based on what I have seen. I did not want to spend that much and enjoyed the challenge of making my own cut off guide.