Thread: Will this work as a straight razor polisher?

I just picked up this double buffer grinder from a local ebay seller. I was wondering if this up to the task of polishing straight razors. I paid $30 so not that big of a loss.

Yep, pretty fast motor, so much care should be taken. I recommend smaller diameter wheels to offset that RPM. I wonder if there is a way to slow it down a bit?

I'm just thinking out loud here, but would a variac be a safe (to the motor) way to slow it down? Any electricians in the house?

That! I hire guys from the School of Automotive Machine. Part of their issued kit is a Milwaukee grinder for porting cylinder heads. Straight out the end, single speed, weighing 4 pounds and running WAY too fast.
They go to the tool place and get a widget to turn em down for 15 bucks. They say it works great. Why not for this? I feel it is that the Milwaukee die grinder has brushes and most 3400 rpm motors are brushless. So I feel that the motor needs all it's voltage to start, but would it burn up as you got it running, cut it down by half, and applied load?

In general:

If a motor has the ability to be Variable speed, it is a huge selling point and only the cost of a different switch so if it were it would be

I am by no means saying it positively can't be slowed down, but I am saying the odds are against it being done easily..

Use 4 inch wheels and use care and light pressure and you should be fine, it will take some practice to learn how to hold the razor and keep a finger on the temp..

Originally Posted by robellison01

I'm just thinking out loud here, but would a variac be a safe (to the motor) way to slow it down? Any electricians in the house?

No. A variac will not make it go slower. It will just make it burn out faster.
You need a frequency drive to turn the 60Hz into 30 or 20 Hz.

Originally Posted by sharptonn

So I feel that the motor needs all it's voltage to start, but would it burn up as you got it running, cut it down by half, and applied load?

The speed is set by the frequency. The voltage gives it power (not exactly, but close enough for basic understanding).
If you cut the voltage, you'll just take away power without reducing the speed (significantly).
If you then apply load, it will slow down significantly, with a sharp increase in motor current.
If that slowdown lasts (because of the load), you'll burn the motor coils.

One other thing to consider is that some cheap speed controllers may mess up the local electric grid.

Originally Posted by Lemur

One other thing to consider is that some cheap speed controllers may mess up the local electric grid.

Yes, that is another thing wort considering. The motor won't really notice, but frequency convertors work by taking 60Hz, converting it to DC and then reconstructing a sinewave of the correct frequency. But it is an imperfect reconstruction. It will be more or less stepped in little increments so that the whole resembles a sinewave.

A good frequency drive will have a close match to a sinewave, while a cheap one will havbe bigger steps, and more importantly: they will also have interference or spikes in the output. None of this has a big influence on the motor, because the motor coils combined with the inertia of the motor smooth out things as far as shaft speed is concerned. But there will be a lot of noise and garbage going down the grid. As a result, you might damage or at least influence other electronics in your home.

That's why it is worth going for reliable brand names, such as danfoss or siemens (to name 2 popular ones) instead of buying cheaper ones at half the price, even though the seem to do the same thing.

well from what i am hearing i neither want to ruin, the motor or spend more than what i paid for it.