Am I abusing my tool?

I have a power drill that has a reverse switch on it. I can hit the reverse switch even when the drill is at full RPMs. It rapidly switches direction. Is this bad for the drill? I guess it’s kinda like hitting the reverse switch on your ceiling fan, but on a smaller sized, yet very much stronger and faster, electric motor.
My buddy swears this act will “burn out the brushes”.

Any power tool experts out there? I’m sure there are tons of electric motor freaks that could answer this too.

I doubt if the brushes will be damaged any more than in normal running for a universal motor but it’s probably a good shock to the drive gears.

A ceiling fan is a bad comparison. They use direct drive induction motors (someone correct me if I’m mistaken) running at low RPM so no brushes or gear train.

It’s certainly causing more wear than just turning it off, switching directions, then switching it back on. So you are putting more current than normal through the brushes, windings, etc. and causing more mechanical stress on the gears and such. The thing is, these are the same things that get a lot of wear and tear when you use the drill to you know, actually drill something. Considering how light weight the mechanical bits of the drill are compared to how much force the drill has to overcome during normal use, I think the extra wear and tear you are causing would be almost negligable.

Still, there’s just something unseemly about intentionally abusing your tools. They should be cared for lovingly. It’s just not right man!

Good God, man! Have you ever seen Toy Story? Take care of your tools!

Are you changing direction under load, or just while spinning the drill? I doubt that changing direction would place more of a load on the drill than using it under heavy load, but don’t blame me if the brushes fly out and hit you in the eye, or whatever…


Are you like Clinton and do so just because you can?

Surely you are not in that big a hurry.

Again, WHY?

If the drill has an electronic torque limiter then the increased current caused by the switching will probably be limited.

If it is an electronic drill, reversing is achieved by means of a lever switch just above the trigger switch.

What happens is that when an electric motor is turned off, the magnetic fields within suddenly try to collapse. The very act of collapsing magnetic fields will then cause another current to be induced which will try to maintain this magnetic field, which then tends to collapse more slowly.

This sudden collapse of fields also causes a large reverse voltage to be induced, and this is directly proportional to the rate of change of field.

When you switch off a motor the reverse voltage is often quite significantly larger than the original supply voltage so the motor winding insulation has to be able to cope with this.

This rate of change will be very much faster than usual if you reverse the polarity switch, hence the reverse voltage induced is going to be very much greater, the motor will stand it in all probability but you would be putting the motor winding insulation under much greater strain. If the motor is already hot, the drill fairly old and well used, you risk shorting out some of the motor windings.

Drills such as this are very robust, it generally takes a lot of ill treatment to damage them, usually things like the switch fail rather than the electrics.

Its possible that the larger current caused by reversing in this way might kill the switch if it is already aged.

The brushes will arc during the sudden slowdown phase and might chip slightly at the edges, which would reduce power and efficiency slightly.

If the drill has mechanical reverse, where you change cogs in the gearbox via a lever on the casing, you stand a good risk of buggering it up completely.

Well, yeah. If I’m piece working then I’m in a pretty big rush. If I’m hourly than I will take my freaking time.

I’m not reversing it under load. But it takes that extra three seconds to wait for it to stop spinning before I can reverse it and remove that dead screw. And then another three seconds to wait to switch it back to start screwing again.

casdave mostly all of that went over my head. But I really appreciate it. You’re saying, though, that the brushes could get chipped from this act? BTW, it’s the kind with a lever above the trigger.

You may wish to upgrade your drill if you’re in that much of a hurry.

My DeWalt cordless drills have a mechanical interlock between the trigger and reverse switch. They also have electric brakes. If the trigger’s pressed at all, the reverse switch is locked in position. As soon as the trigger is released, the reverser is usable. By the time your finger is off the trigger, the brake has stopped things entirely, making it safe to change directions without waiting.

If you’re able to reverse at will while running, you’re putting the motor into a dead stall condition while it’s trying to overcome the inertia and change directions. Not too good for it, plus all the badness described below about collapsing magnetic fields and strain on the gears.

It is a DeWalt. VSR257. I don’t reverse while still holding the trigger. But I reverse while the head is still spinning.

But I don’t know what brake you’re talking about. It still spends when I left off the trigger. It has to slow to a stop. Buddy says let is stop completely before reversing. I’m wondering if that is necessary. Will it hurt to reverse while it’s still spinning?

This is good. The reverse switch is often a cheap piece of junk, a sliding copper spade. Arcing can quickly destroy these.

With the brake, the chuck stops spinning immediately when you release the trigger, rather than coasting to a stop.