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I have a Makita electric drill. It's about 25 years old. It's a red one; back then the red tools were the "professional" models and the blue ones were the cheaper "homeowner" models. The problem I have with it is that it is really noisy. If sounds and vibrates like it has bronze bushings that are spinning in the housing. Taking it apart, I see all the bearings are sealed ball bearings and are in good shape - they spin easily and there's no play. The gears look good - no chipped or missing teeth. The case isn't cracked or broken. The brushes are worn, but there seems to be plenty of room left on them and the springs seem OK.

When running, there is some arcing on the brushes. It's variable speed, so noise and vibration increases with speed.

Question: Do you think this is a brush problem? Can you dress the brushes somehow to get her working like new again? Any ideas to track down the problem?

Fran really likes the drill as she finds our other drills too heavy and bulky. If this one can be fixed, I stand a better chance of finding a drill when I need one.

How's the fit of the bearings on the shaft? If it's too loose, the shaft can "walk" around the ID of the bearings. But that's usually intermittent and can be stopped sometimes by smacking the tool while it's running.

All four bearings seem to fit really well on their shafts and in the case. I gave it a few smacks as you suggested; didn't help.

Dang. That's too bad. I often rely on percussive maintenance. Sometimes it works.

worn gears .... put a bit of heavy grease on gears and try again

Bill

If Bill's grease on gears test does not quiet drill.

My guess is bearings. Sealed bearings are hard to evaluate or test. The age and increase in noise with speed, indicate bearings IMO. You would have to take them out and rig up a way to spin them to hear the noise. I realize you say they are good. You say gears are good and etc. But logic says something is bad and you didn't notice. So I have to give my opinion.

Sometimes an armature with a few shorted windings will develop a hammering type noise caused by internal stresses. Look closely at the commutator where the brushes ride. If the leading edge of one or more commutator bars shows deterioration or burning and the brushes have a ragged looking edge, that's a pretty good indicator of winding problems. Back when we rebuilt our own starters and DC generators, just about every good shop had a "growler" for testing armature windings. I've still got one stashed away somewhere, but I haven't used it in years.

You can spin-test a sealed bearing by holding it against a wire wheel buffer on a bench grinder.
Jerry

Yup. It's the gears. Took out the shaft with the chuck and the big gear on it. Closed up the case, so the motor was in the case by itself. Plugged it in and tested it: the motor ran smoothly. Reinstalled the chuck shaft and put lots of grease on the gears. It ran a bit better, but still not well.

You can buy replacement brushes and bearings, but not gears. I'd rather repair than replace, but if parts aren't available there's not much you can do.

"You can buy replacement brushes and bearings, but not gears."

That's not necessarily true Gord. If that were mine I'd check Boston Gear and some of the other manufacturers. Also making gears from scratch is not out of the question. It does require a milling machine, dividing head or other indexing attachment, and the correct gear cutter for the gear you are making. Yours is not a lost cause.

Thanks, Ray. That's too much work; I writing the thing off.

She's getting a new drill for Christmas! Light weight, rechargeable and key-less chuck.