Cut Off Saw From an Angle Head Grinder




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 ...

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.

3 People Made This Project!


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22 Discussions

Phil BYonatan24

Reply 3 years ago

I appreciate the affirmation, but the idea came from something I saw at Harbor Freight.


4 years ago on Introduction

Hi great instructable, am looking into making one for myself but with the added benefit of being able to change between 90 and 45 degrees easily. My idea would be to add a pivoting fence made out of angle-iron and bolted at the grinder end and a series of pre-set hole at the other end of the fence and base up-to 45 degrees held either with a loosely assembled bolt of pin.

1 reply
Phil BGillerUK

Reply 4 years ago on Introduction

Good idea! Thank you for looking. Please post a photo when you have completed it.


5 years ago on Introduction

This is just what I was looking for. Thanks fo posting. Just a question: the guy that was worried about safety perhaps exaggerated a bit but, in your experience, is tinkering with power tools such a bad idea?

3 replies
Phil BI_StarkGuy

Reply 5 years ago on Introduction

I have never had a problem or even felt at risk from something like this project. Follow all of the safety precautions you can, especially for safe usage. Use good sense and try to anticipate what could happen so you can avoid all such things.

What I think of as dangerous with a grinder such as these handheld units is: a) I have heard of a cutting wheel that shatters and flying pieces of it sever an artery so that the user bleeds to death in a few minutes, or b) the cutting wheel catches in a piece of steel so that the wheel jerks and badly cuts into the users leg. Both of those scenarios could happen with a tool out of the box. Neither is more likely to happen because of the modification I showed here. Thank you for looking.

I_StarkGuyPhil B

Reply 5 years ago on Introduction

And I think you can avoid the two bad scenarios by simply making a straight cut and allowing enough time for the wheel to cut through the material. Also wearing a face shield improves safety exponentially.

I don't have a welder so I will have to make my saw in another way but using yours as a basis. Would you mind if I post an Instructable of my model while giving you credit for the original idea?

I'm following you.

Phil BI_StarkGuy

Reply 5 years ago on Introduction

Please do publish your idea. I actually got the idea from something I saw at Harbor Freight.

Great 'ible! I'm hoping you'll take it to the next stage where you can cut up to 45 degree angles - that would be perfect for me! lol! Maybe it could turn on it's axis with a bearing of some sort?

1 reply
Phil Bbricabracwizard

Reply 6 years ago on Introduction

Commercial cut off saws for steel do not tilt the arbor like a power miter box does, but they have an adjustable fence on the table that angles to 45 degrees. It is very easy with the saw presented here to angle the fence so the steel is cut at 45 degrees.

Thank you for looking and for commenting.

the cut dust and sparks are very open. this is sedentry so use is dangerous as we have to move the object to cut. no use is machine stays. pls make it more different. but good concept keep it up dear sir

1 reply
Phil Bbannutechniclor

Reply 7 years ago on Introduction

I am not sure what you are talking about. I do not move the steel, but the grinder is hinged and the steel is stationary. Further, I can use this with the factory guard, but usually the sheet metal deflector for the sparks is more than sufficient. I wear a face guard, too, when I use it.

I saw your design. I notice the grinder is held in place with only one bolt. It appears to me the grinder could twist on its mount and bind against the steel being cut. It also appears to me you have no fence to hold the steel from moving as it is being cut. My grinder is held very firmly in place and cannot twist or move in its mount.

My design is an adaptation of a design once sold by a tool company (Harbor Freight) in the USA. Thank you for your comments, but after about ten years of use, I do not see any safety problems with the unit I built.


7 years ago on Step 9

Nice design and all but I really see lots of possible danger here for a serious accident. Modifications of tools often lack of properly engineered safety design and lead to horrible accidents. Yes I have witnessed lots of modified tools especially powered ones that harmed or killed people. Upside down bandsaws, skilsaw attached to a table upside down, unguarded blades and methods of attaching rotating power equipment that can bind or be thrown off and where improper access to switches were improvised.

Go ahead and curse me for wanting people safe from dangerous and improperly designed tool modifications. When your finger or hand gets cut off then you'll stop. This can throw a chip off the blade, loosen in the vice you made for it which is squeezing the motor chassis. Just as bad mixing electricity with water, mixing power tools with modifications FAR FROM THE INTENDED AND LICENSED SAFETY ORIGINAL DESIGN...

How would you feel Phil B if someone looked you up and told you that one of your improvised safety power tool modifications caused them to lose a limb? Or a life of a family member? Just looking at your skills and placement of the tool cutting blades lets me know you are not qualified to design and scary configurations of your contraptions are DANGEROUS!!!!!!!!!

Can you show us a way to put safety guards on your devices and a way to insure clamps at motor casings and switches can be operated properly as to the tools' original safety design? I don't want anyone hurt. Especially not you.

1 reply
Phil BCooldeal

Reply 7 years ago on Introduction

After some thought, I checked and it can be operated as shown with the original guard in place.


9 years ago on Step 11

you should use a cable tie to hold down the grinders switch and make a a foot operated momeruntry switch and plug the grinder into that

1 reply
Phil Bharvey639

Reply 9 years ago on Step 11

If I used this tool more regularly I would probably do that. Thanks.


10 years ago on Introduction

Excellent idea! I just happen to have a extra angle head grinder that could be converted into one of these. Just the thing for those smaller cut-off projects.