Grinder From a Microwave Blower Motor

What’s up everybody? Today I’m going to re-purpose a salvaged microwave blower motor from an over-the-stove microwave and turn it into a small bench grinder.

A salvaged microwave
Hand tools I.e. screwdrivers, nut drivers, snips, wire crimpers, ETC.
Safety equipment such as gloves and eye protection
Detergent or crud remover and a brush

wire nuts or connectors

Extra wood and some method to mount (I use clamps since I store it under my workbench when not in use)

Grinding wheels

Something to sharpen or polish

CAUTION: PLEASE LOOK UP METHODS TO DISCHARGE THE CAPACITOR!! THE CHARGE THE MICROWAVE CAPACITOR CAN STORE CAN SERIOUSLY HARM AND/OR KILL YOU. EXERCISE EXTREME CAUTION!!!!!!!!!!!!!!!

I apologize, but I did not get any photos or video of the teardown of the microwave. However, every microwave is different and tearing apart my particular one might not truly benefit everybody.

A word of caution, but there are sharp edges and stuff they could hurt you so make sure you stay safe. Also if you’re going after the magnetron part of the microwave just be aware that there is dust that could go airborne that could be harmful to your health. I don’t remember exactly but I believe that it is either bismuth or beryllium.

There are many useful parts of an old microwave (such as the asynchronous motor) but I am after the blower motor, in particular. After I procure my part, it desperately needed a bath...

I saved the plastic blowers (pic 2 and 3) for the plastic part I will sand away to mate to the shaft later. It will make more sense in part 4.

Once you have your motor isolated and cleaned up, you are ready to get it prepped for your station. Looking at my schematic picture, the orange and red wires go to the capacitor (mine is not polar so orientation didn't matter). The blue wire goes to the high speed and the yellow wire goes to the low speed. As I explained in my video, I’ll use the yellow wire thinking that since it’s slower speed it will have higher torque. And finally the white wire goes to neutral.

Once I have everything connected and isolated to protect myself from the 10 µF capacitor, I switch it on (and by that I mean I plug it in since I actually do not have an in-line switch) to ensure it is working properly.

The next thing to do is to make a base for it and properly isolate the capacitor for everyday use.

Once everything is working properly, I used some particleboard and screwed pieces together in order to make a base. I got some grinder wheels from the hardware store to attach to the shaft. I also had some stop collars from my used parts bin that I use to ensure they did not fly off.

I use the plastic piece from the original blower fan to act as a coupler between the grind stone and the shaft, if that makes sense now, and so far it’s worked great. Later on, I used a spare bit of particleboard to make a "polishing" wheel. It mounts directly on the shaft but I had to dissect the metal housing as you can probably see in picture 4, as well as my smaller version that doesn't even work. You cannot hone an edge if you cannot get the blade to mate with it...turns out.

I have some magnets on the base to "store" tooling, like an Allen wrench for ease but I do that with all my tools.

That is basically it. I used a broken piece of equipment to make another new piece for my shop. Thanks for looking and be on the lookout for my next one!