A device for a screwdriver from the gearbox of a broken angle grinder

Every tool has its time. But this does not mean that it should be thrown into a landfill, because some of its parts can still be used. For example, as in today’s case with a broken angle grinder (angle grinder). Let's try to make an interesting device for a screwdriver out of it.

For this homemade product, we only need the gear part from this power tool. This part is removable in most grinders, and sometimes even remains “alive” after their final use. It is important for us that the gearbox housing is intact, the bearing and chassis are working, without slipping or, even worse, jamming. You will also need a small piece of shaft attached to the rotor. Well, shall we get started?

We turn the angle grinder gearbox into a tool

The first step will be to separate the gearbox from the rest of the grinder body. This is not difficult to do; it is usually square in shape and secured with screws at the corners.Perhaps for this separation it will be necessary to start dismantling the electrical part of the tool, remove the brushes, the start button, and then the rotor with the shaft and gearbox.

The gearbox needs a complete overhaul. We disassemble it completely, removing all retaining rings and gaskets. If necessary, we replace the bearing; it most often fails in this tool. This is due to the activation of metal elements at high speeds, and the entry of microparticles into the lubricant, and then into the bearing housing.
This angular gear transmission involves two elements - the drive gear (small, located on the shaft) and the driven gear (wider, located in the gearbox itself). Due to the difference in the number of teeth, the transmission speed is set and the speed of rotation of the gearbox shaft is regulated. We dismantle the drive gear by unscrewing the nut on the rotor shaft with a suitable wrench.
For our device to work, you will need a piece of shaft 7-8 cm long. It may be necessary to cut off part of the rotor housing to do this.

When all the components are ready, you can begin assembling the gearbox with a section of the rotor shaft. We place the drive gear in its place on the rotor shaft and tighten it with a wrench.

We connect the air separation gasket and the gearbox housing with four screws, which we then cut to length flush with the nuts.

The outgoing section of the rotor shaft needs to be modified. We clamp the gearbox in a vice and fix its shaft with a clamp. The rotor shaft, in turn, is worked with a grinder to the shape of a tetrahedron. The most convenient way to do this is with a sanding disc. Using a caliper, do not forget to measure the accuracy of the size, which corresponds to 6.5 or 9.5 mm (depending on the mounting size of the screw heads).

Important! The more uniformly the shaft is ground, the more accurately its center of rotation will be located, and therefore the backlash when rotating the tool will be minimal.
The gearbox attachment is ready, all that remains is to clamp the rotor shaft into a screwdriver or drill and check it in action. The tip of this device, namely the gearbox shaft, allows it to be used as a wrench or a device for tightening self-tapping screws. It can be used in hard-to-reach places where the body of a conventional tool does not allow this. Just like that, practical, cheap and easy!

Some practical tips

Of course, such a device cannot be made manually. To work, you will need a grinder (working!) with cutting and grinding discs, screwdrivers, pliers, pliers for retaining rings and terminals, a hammer and wrenches. You may need a puller to remove the bearing.
And when assembling the gearbox, do not forget to fill it with lubricant, as grinder manufacturers do. This will extend the life of your instrument. And at the right moment he will help you out, because as you know, a spoon is precious for dinner!