Why Does an American Hand Grinder Cost $345?

The other day I had to get a bolt out of a rusted nut, and the only way was to destroy it. There was no way to get good leverage to twist it, and it was in a place where I could not heat it. Enter the drill.

My plan was to drill straight down into it through the end. The drill bit would cut into the threads and loosen the remains of the bolt. In order to do this, I needed a way to make the bit center itself in the end of the bolt. Otherwise, it would walk around and give me an off-center hole.

I have a Dumore hand grinder. Tool people love these things. They are American-made tools similar to Dremels, but they’re bigger, and they only have one speed: maximum. My Dumore’s top speed is (was) 25,000 RPM.

I got my Dumore on Ebay. It was barely used. I thought it was a bargain. They sell for $345 new, and I think I paid something like $45. Anyway, it wasn’t much.

The Dumore ran, but it faltered a lot, and I had to spin the spindle by hand to get it started. I figured it had bad brushes or something, so I didn’t send it back.

I got it to run while I was working on the bolt. I used the Dumore to put a cup-shaped hollow in the end of it to keep the drill bit from wandering. After that, I decided it was time to fix it. I checked the commutator brushes, which looked new. On the advice of a forum guy, I filed a little bit off of their ends to make them conduct better. I also cleaned the commutator with Scotchbrite and De-Ox-Id, which is a product made for cleaning electrical contacts.

When I put the grinder back together, it wouldn’t do anything at all.

I thought I had to save it. I had a wonderful American-made industrial tool in great shape, apart from not working. It was worth working on. Surely.

I sought advice and did a bunch of things, and nothing worked. Finally, I looked at the armature wires under magnification. Most of them were detached from the commutator, so there was no hope at all that it would run. Current would not go through the commutator.

I believe this explains the grinder’s willingness to run after I spun it by hand. In order to run, it needed current to go through the armature windings, and that meant it needed them to be connected to the commutator bars. When I spun it, I moved the brushes from disconnected bars to connected bars, and the grinder ran. This is my theory.

I went to Dumore’s site and looked at their parts area. They had a diagram of a similar grinder. The commutator was available, but of course, it was part of an armature. The armature sold for the low, low price of about $128, plus shipping. I contacted Dumore, and they told me the armature didn’t fit my grinder. They didn’t make armatures for it any more. They recommended a guy named Larry, in Detroit. I called him, and he laughed. He said he hadn’t seen a grinder like mine in around 20 years. He did not have any armatures.

I started prying the tiny commutator bars open and soldering the wires back on with a magnifying visor, but then I thought about it. The soldering would take maybe 4 hours, and then I would have a tool which might be unbalanced because of the presence of the solder. The armature had been balanced at the factory, prior to my work, and you can’t balance an armature dynamically at home. An armature which is balanced when at rest may go nuts when it spins. This must be due to other problems in the inertial tensor, which only motion can reveal. My guess. You could make an object with perfect distribution of mass around an axis that still had uneven distribution relative to other references. Imagine a cylinder like a rolling pin with a pound of lead at one end and another pound at the other end, on the other side of the axle.

While I was doing all this, I was also thinking about new grinders. I am not poor. I can buy a $345 grinder. Maybe that was the answer. Bite the bullet. Get it over with. Move on. I would have a great grinder for the rest of my life, and I would never miss the money.

Then I did more studying.

My grinder is about 12″ long. It has a grand total of two bearings in it. It has a heavy plastic body. It has a crummy on-off switch held in place by the pressure of the rear plate, which screws onto the back of the grinder. It doesn’t seem all that great.

People claim Dumore grinders run forever, and what you pay for is the quality of the parts and assembly. They’re smooth. They’re balanced. Unlike other grinders.

Are these things really true?

No. At least it doesn’t look like it.

Guess what Dumore charges for the high-quality bearings in my grinder. They charge about $4.40 per bearing. I’ll tell you something I have learned as a tool person. Really precise bearings don’t sell for $4.40. They are very expensive. Conclusion: Dumore doesn’t use fantastic bearings that last longer or run smoother than regular bearings.

I looked at Makita. Their model GD0603 is about the size of my grinder. It has 25% more power. Guess how many bearings it has. Four. One is a lot bigger than the Dumore bearings, and big bearings distribute wear and heat much better. The Makita’s bearings cost more to replace.

The GD0603 has a nice quality on-off switch. It has a nominal speed 3000 RPM faster than the Dumore. It comes with a wire bail so you can hang it and put a flex shaft on it. It has a two-prong plug instead of three prongs because Makita insulated it properly.

Makita sells every part of the grinder, and it’s easy to take apart and repair.

Wait…Dumore is a high-end company. They put the money in the armature. It’s balanced better than the Makita, and it runs smoother.

Really?

Makita started as an electric motor company, and here is one of the things it was known for: balancing armatures. Makita still balances its armatures dynamically.

Ooof.

Makita also powder-coats its stators so they don’t short out when junk gets in and lands on them. Dumore…not so much.

The Makita sells on Amazon for $124. I looked at reviews. Some guy said he bought his first one in 1998, and he only replaced it recently. Did he have to replace it? I doubt it. Every part can be replaced. Even the armature, which, though BALANCED, costs under $20.

Here is what I can’t figure out: how can the Dumore possibly be worth three times the cost of a Makita? Not only do I not see how it can be better; I can’t see how it could be anywhere near as good. Yes, the Makita is made in China. So what? Makita is a Japanese company, so I very much doubt they make garbage in China, and anyway, grinders are very simple machines.

I got a Makita. I will probably throw the Dumore out. I may get a bigger Makita, too, since I can get both Makitas for a lot less than one Dumore.

Once again, I feel I got stung by the old iron bug. “Old iron” is what stubborn old coots call ancient American tools. They go to their graves making fun of Asian tools and shrieking that anyone who is too cheap to pay the extremely large premium for Caucasian-made tools is a fool. Sometimes they’re right, but the problem is that they can’t tell when they’re wrong, which also happens a lot.

I think the Sino-Japanese Makita is head and shoulders better than the American Dumore ever was. Maybe an engineer could explain why I’m wrong, but I don’t see a way for him to approach the Makita in order to attack. Cheaper. Better bearings. More bearings. Better switch. Insulation. Low noise rating for protection-free grinding. Lower cost. Balanced. Cheap parts readily available. Easily repaired. More powerful.

Why do old Dumores last so long in commercial shops? I think it’s because they have to, just like American cars that last 80 years in Cuba. No one wants to spend hundreds of dollars to replace a hand grinder. A $128 armature and 9 dollars’ worth of bearings make more sense than a new $345 grinder. On the other hand, throwing out a Makita that costs a third as much isn’t intimidating. If Makitas don’t last as long, I think it’s because people can afford to throw them out and replace them. They would probably last as long as Dumores or longer if people felt motivated to treat them well and repair them. I’ll bet if Makita made no changes other than raising the price to $1500, they would last 50 years. People would say, “I paid a lot for that Makita, but I’ve rebuilt it 10 times, and it runs like new.”

If I’m wrong, explain it to me. But you can’t mention the bearings, construction, materials, or balancing, because I’ve already considered those things. Good luck.