Offcuts: More Melted Tools By: Don Heisz

A few days ago, while at work, a guy was watching me use my new brushless cordless grinder. He came over and asked me how it was.

“I don’t really know, yet,” I told him, “I just bought it a few days ago.”

“How much was it?” he asked.

“It was about $160 with no batteries,” I told him. “All I can say about it right now is that it’s really quiet.”

“I noticed that,” he said. He was a sheet-metal worker, a duct guy, a tin banger, now called an HVAC technician, like that means anything more or less, and so used to noisy grinders. And there’s practically nothing noisier than a grinder cutting a duct.

“I had to get it to replace one that stopped working,” I said, “I had one for quite a while and it stopped working. I thought the brushes were worn out but it was faster to just get another one than order brushes or bring it somewhere to get them replaced. So, I got one just like it and it didn’t last very long at all.”

“No? Why not?”

“I thought the brushes went in it but when I tried to check that, I couldn’t get the plastic caps that cover the brushes off.”

broken cordless grinder

Above, you can see the damage heat inflicted on the poor, defenseless plastic cap.

“I saw that the plastic caps that cover the brushes had actually melted and run right down to the commutator. ”

“Wow,” he said.

broken cordless grinder

Above, you see what happened after I smashed off the plastic cap and tried to pry out one of the brushes. Below, you see it would not come out.

broken cordless grinder

“Yeah, so two grinders with plastic melted down into the motor. They both work otherwise. Well, they can’t actually work because of the plastic but I mean that’s all that’s wrong with them.”

“Why would they make covers that would melt?”

“Well, this one is brushless. So, there’s no danger of the brush covers melting. That might make it last longer.”

broken cordless grinder

Above, you see the motor which has a large amount of ground steel attached to every magnetic surface. (Note the rust – that is the result of being in water when my basement flooded.) Below, you see the plastic brush housing.

broken cordless grinder

Anyway, some of you may recall I wrote about melting tools previously. At that time, I only knew that I could not remove the brush caps on either the grinder or the circular saw. Now, I still have not checked the circular saw, other than to confirm I can’t remove the caps, but I expect it has suffered the same problem. The saw, however, was, in my opinion, abused. It was used to cut some long strips of aluminum and that made it heat up quite a bit more than it should.

You know, a tool might be able to do something, but that doesn’t mean it should. In this instance, that saw can cut aluminum, but the toll on it is too heavy.

The grinder, however, is another matter. You should be able to use a grinder without it self-destructing. A grinder grinds and cuts metal and that is what these ones were doing. If there were special instructions saying “Use for 2 minutes, let rest for 20” I would likely not ever buy it.

broken cordless grinder

Above, you can clearly see the melted cap plastic around the brush holder, but the white plastic itself is not really very melted – it’s obviously a superior plastic. Also note the carbon is cracked, but I have no idea what did that.

In this instance, it’s a problem that could be solved by making caps out of metal or Bakelite or any of a hundred heat-resistant plastics. Or, for that matter, stop making the tools out of junk and put a few pennies in where it counts. Why is there plastic that can melt into the motor?

I’m sure some other problem awaits the new “brushless” grinder. Maybe the rats that run on the wheel inside it will die after a few months.