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. https://www.instructables.com/id/Too_Much_Flex_in_a_Circular_Saw_Base/
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. https://www.instructables.com/id/Making_a_Square_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.