It is difficult to cut a straight line by hand with thin cut off wheel in an angle head grinder. I had an angle head grinder and wanted to make a mount for it to convert it to a cut off saw. I know you can buy a mount at Harbor Freight Tools, but I have a bias against most of their tools and wanted to make my own. I also have a welder. I used scraps of steel I already had.
Step 1: Basic piece for a start
A friend gave me some scrap pieces of steel. One of these was a piece of 1 inch square tubing about 22 inches long with a 90 degree bend at one end. For a long time I had no idea how I would make use of this piece. If you choose to make a saw like mine, you probably will not have a piece like I had, but you can use other things. You could even weld a couple of pieces of square tubing together to make an "L" shaped piece.
Step 2: First step
I cut about 9 1/2 inches from the straight end of the square tubing and welded it in a "T" to the end of the 90 degree curve. See the Sketch up drawing to see how the parts are positioned for welding the two pieces of square tubing. Then I welded two door hinges to the 9 1/2 inch piece.
Later I added a magnet from a hard drive. It makes a convenient way to store the bolts for securing the grinder to the mount attachment. The magnet is visible in the lower right of the picture.
Step 3: Weld a base
I had some 3/4 inch square tubing I used to make a base for the cut off saw. The narrow slot between the two extra pieces in the center is positioned so the cut off wheel fits into it. Welding a frame of steel sounds easy, but it takes some special care to have a frame that lays flat when finished.
Originally I used some scrap chip board shelving for a base. That worked pretty well until I used some water to cool steel I was cutting. The chip board swelled and I decided to replace it with a steel frame for the base.
Step 4: Weld the hinges to the base
Here you see the welds for attaching the hinges to the base. My welds are not very pretty. I found it a little tricky to weld the edges of the hinges to the corner of the relatively thin square tubing, lest I burn through the tubing.
You can see something extra on the right hinge. I will explain that in the next two steps.
Step 5: Depth of cut adjustment--part 1
Here you see a partially used cutting wheel on the grinder and a new wheel. I wanted a limiting stop to regulate the depth of cut as the cutting wheel wears.
Step 6: Depth of cut adjustment--part 2
I drilled a 5/16 inch hole into the right hinge under the lateral piece of 1 inch square tubing. I drilled a hole in a square of thicker steel and tapped it for 1/4 inch x 20 thds. I welded the square of steel over the hole in the hinge. Then I inserted a 1/4 inch bolt with a locking nut on it. This allows me to change the limit stop on the saw as the blade wears. I found this a helpful addition to the cut off saw.
Step 7: Vertical support for the grinder
I welded a piece of square tubing in vertical position to support and attach the grinder. It is long enough to reach down to the tapped mounting holes in the grinder head.
Although it comes later, you can see the 1/4 x 20 nuts I welded to the main arm to receive the bolts that hold the grinder firmly against the arm. The nuts distorted a little during welding and I tapped them after welding.
Step 8: Cut the vertical and add a horizontal piece
Cut the vertical piece from the last step to length and add a horizontal piece at the same height as the tapped holes in the grinder head. It is important that you make sure you keep the grinder aligned at each step so that the cutting wheel will be at 90 degrees to the base and also 90 degrees to the fence you use. You want your cuts to be square when you use the saw. There is the possibility of compensating for any error as you go.
I used 1/8 x 3/4 inch strap iron across the ends of the horizontal piece. Before putting them in place or cutting them to exact length, I welded a nut to the end of each piece. then I drilled them out so the mounting bolts can slip through them with ease. (The visible welded nut is painted yellow.)
I clamped the grinder in place and lined it up as precisely as possible. I screwed one bolt into the grinder head with its strap iron and welded nut in place. Then I clamped that piece of strap iron to one end of the horizontal piece. This allowed minute adjustments before tack welding. Then I attached the other piece of strap iron and checked to make certain the cutting wheel was still in alignment. I clamped it and tack welded it. Then I finished my welds and cut off any extra strap iron from the ends closest to the camera.
Step 9: Upper mount for the grinder
I used a piece of 1/8 x 3/4 inch strap iron to hold the upper portion of the grinder against the main arm. I had to grind a triangular notch into it to fit around part of the grinder case. I used 1/4 inch bolts and made thumb adjustment levers for them from 3/16 inch rod bent at an angle and welded to the bolt heads. Step 7 shows the attachment of the nuts to the main arm.
Step 10: The fence
The saw needs a fence to hold work pieces against the rotation of the cutting wheel and to assure accuracy. I used a piece of angle iron from an old bed frame. I welded two tabs to it so I can clamp it in place with "C" clamps. I made two small nicks in the base frame with a hacksaw so I can quickly align the fence again if I remove it to cut something without the fence.
I may yet modify the way I mount the saw for use. Currently I use a couple of larger "C" clamps to mount it on the top of a saw horse.
Step 11: The shower of sparks
Perhaps I should have mounted the grinder rotated 180 degrees clockwise so the cutting wheel would be on the right side of the grinder rather than on the left side of the grinder. But, I prefer to look at the work from the left of the cutting wheel and to use my right hand to operate the saw. The price I pay for that is the shower of sparks shoots back at me rather than toward the front of the cut off saw. I made a sheet metal deflector I clamp to the cut off saw's frame. It works very well. Before I made it, I ruined a good polyester sweatshirt.
To use I simply squeeze the grinder's switch with my right hand while lowering the saw into the steel I am cutting.
Initially I would mount the grinder when I needed to make a precise cut. Then I would remove the grinder when I needed to grind or cut something freehand. Eventually I got some Christmas money I used to buy a second angle head grinder so that I can leave this grinder in the cut off saw attachment.
This has been a valuable addition to my workshop.