Powerdrills with sliding brush reverse motors

[Andy Dingley]

Until recently, mains powerdrills were reversible (if at all) by a small switch near the trigger. Nowadays it's becoming universal for reversing to be done instead by a sliding brushplate and a mechanical switch that moves the brushgear around and changes its phasing relative to the stator poles.

Why the change ? Is this a good thing or a bad thing ? What are the advantages in terms of torque, reliability etc. ? If it's such a good idea, why did no-one do it for years, then suddenly they're all at it ?

[Pete C]

I've only seen the rotating brush plate system on Bosch and Skil drills, maybe they hold a patent on it. A lot of drills have 'reversing brushes' which sounds similar but just reverses the connection to the brushes and stator. This is often done with a sliding switch through the drill body so it looks mechanical.

I bought a Skil mains drill about 12 years ago, and it was quite well priced then for a 550W drill with speed control. In use it was unbreakable, used for a lot of sanding and driving large wood screws. Plenty of torque, could drive aforementioned screws through 18mm ply if I wasn't careful...

These days the cost of production is much lower so using a switch with maybe less reliability is not so bad.

cheers, Pete

[Mr Fuxit]

It's a change back, and it's a good thing! It means that torque is the same, or better, when in reverse, and reliability is, from the warranty point of view, much greater, as there is no chance of an idiot switching between forward and reverse without allowing the drill to come to a stop, thus damaging the transistors and I.C.s that would otherwise control the direction of rotation. Like everything else, power tools are subject to trends in fashion; not all them are of real benefit to the buyer/user.