A Power File From an Angle Grinder

This time I'll modify probably the most popular power tool of any workshop - an angle grinder - to a power file. What is more important this project could be done with basic tools like a saw, cordless drill, and angle grinder.

How I did it - you can check by looking DIY video or you can follow up instructions bellow.

For this project you will need:

Materials:

M14 coupling nut;

25x25mm and 20x20mm square steel tube;

M8 bolts, nuts, and washers;

A pair of bearings. I used 24x8x8mm;

Plywood of 15mm thickness (or other thickness);

Wood glue;

Belt sander from regular belt sander;

5min epoxy (or another fast curing epoxy);

A spring in 15-18mm of diameter. Stiffer one will be preferred;

Tools:

The angle grinder;

Belt sander with 80 grit sandpaper or just a piece of sandpaper;

Miter saw or hand saw;

Drill and bits;

Hammer;

A hole saw and forstner bits for drilling;

Clamps and some other usual bits and bobs which is laying around the workshop.

I took this M14 coupling nut, which turns into a roller during the process. I planned to use some hardwood around the nut, but later on, decided to glue a few pieces of the plywood to achieve higher strength. 3 layers of 15mm plywood will be exactly the same height as the coupling nut.

The miter saw, glue and clamps do their job and that plywood brick was made.

The outer roller shape was cut with a hole saw, and the inner hole by using the forstner bit with centering template assistance.

A strong hit with a hammer left precise shape and indication of how much plywood must be chiseled out to make a perfect fit.

I used 5 minutes epoxy to glue the coupling nut inside the plywood roller.

When the epoxy was rock solid - started to shape the needed roller form. First I cleaned both ends. Second - used the angle grinder and a belt sander to make the roller perfectly round. And third - I found the middle of the roller and sanded down a slight angle from sides to the middle. This roller shape will act as a self-adjusting belt guide and will keep the sanding belt in place.

By using angle grinder shaft as a reference point found the ideal place where the square tube should be attached. Also marked how mutch the angle grinder guard should be trimmed to make enough space for all upcoming parts.

The square tube will be attached with two M8 bolts so I drilled two holes on the angle grinder guard and after that repeated that on the square tube.

I used 25 by 25 millimeters square steel tube and cut 13cm length piece.

By drilling the small hole first I got a better centering point for a bigger drill bit. This also made it easier to drill a larger hole.

The square pipe is a bit offset from the needed roller center line and it should be spaced 9mm from the guard. So I used these three washers made from 3mm steel to align the pipe and roller centers. Added one more custom cut steel washer under the nuts to spread bolt tightening force into a wider surface.

The next moving part will be made from 20 by 20 millimeters square steel tube, which nicely fits inside the 25mil square tube.

To keep the sanding belt always tensioned I’ll use this spring under the smaller square tube. The spring sits on the first bolt, which can’t be said about the square tube. The spring should not get stuck into the pipe. Not a big deal, few cuts with the angle grinder, a bit of hammering, and the support surface were done.

I’m planning to use this sanding belt which is made for a regular belt sander. I already measured that the total length from one side to another should be 24 centimeters. Secured a metal ruler with a pair of magnets in place and marked a few reference lines with 1-centimeter spacing on the smaller tube. By compressing spring I found that the perfect travel should be 1 centimeter. So I marked the place where the ruler shows zero and added that additional centimeter for spring compression travel. Cut with the angle grinder on the mark to get the final length.

One end of the smaller pipe will sit on the spring, while another one should keep sandpaper rolling. A pair of the small bearing will make it possible. I used 24 by 8 millimeters sized bearing with the 8 millimeters inner hole. The width of two bearings stacked together will fit perfectly inside this tube.

Marked and drilled the hole for the bolt which will secure bearings in place. After that cut and trimmed the metal to get a nice tight slot for bearings.

Some final shaping was made with the angle grinder and a belt sander. Added a very thin washer in between the square tube and the bearing to ensure that the bearing will no rub into the tube.

As I mentioned before I’m planning to use the regular belt sander sanding belts. As they are way too wide for this power file I simply cut them it to my preferred width. This one was cut to 3-centimeter width. This power file setup is capable to use from 16 to almost 40 millimeters width sanding belts.

I spun the belt by hand to check if everything is straight and the shaped roller is keeping the belt aligned in the center. And look like it does.

To blend in all fabricated parts to the angle grinder - I made a quick spray can paint job.

Here some test sanding on different materials. It is no matter if you need to clean a very rusted metal surface or to trim sharp metal edges - this power file makes this job very easy. Together with fast work, it also provides very precise grinding control.

Talking about the wood - this beast eats it like butter.