I am not about to argue against something I have never used but it may be worth considering what a guy called Forrest Addy had to say on WoodCentral. He is one of the folk who really do know their onions and is worth listening to. This response by him was to a query from someone who wanted to slow their grinder down as they thought it would cut cooler as a result. However the same logic holds good for a number of situations.
QUOTE
Any way to slow down a 3600 RPM grinder? (Joern Larsen, SF Bay Area, CA)
Why slow down a perfectly good bench grinder when the problem you may be having with overheating your cutting edges is due to your grinding wheels being dull and neglected.
The reason for the success of the newer slower speed grinders (1800 Vs 3600 RPM) is ignorance and pandering. The object of this wasteful purchase is ostensibly to prevent the overheating of edged tools when grinding them. The result is when purchased the problem recurrs as the original factory dress on the grinding wheel dulls.
Dispelling the ignorance:
The reason tools overheat while being ground is friction. When the grinding wheel is clean and the abrasive grains in its surface are sharp, they cut cool and efficiently. Any edged tool dulls in use and that as true with the abrasive grains in a grinding wheel as it is with a chisel or plane iron. When the abrasive grains become dull from use they tend to rub not cut and ever-increasing effort on the tool against the grinding wheel is necessary to sharpen it it. Thus the tool overheats, turns blue and the temper is lost. A tool will overheat as readily on a 1800 RPM grinder as it will on a 3600 RPM grinder.
Solving the problem:
Learn to dress your grinding wheels. Make/buy a diamond wheel dresser on a hand shank so you can dress your grinding wheels, making them round, and thereby removing the dull grains by knocking them out of the bond to expose fresh sharp grains. A suitable diamond dresser would be a small cluster diamond such as found in the link for less than $40.
A suitable shank could be made from a piece of 7/8" round bar 12" long by drilling a 7/16" hole in the end 1" deep and cross drilling and tapping for a set screw. This is a life time tool when used in the home shop for the weekly grinding wheel tune up. Your grandchildren will pass it almost unscathed to their grandchildren and they will use it to dress their grinding wheels into the 22nd Century.
Exposing the pandering: when a market opportunity occurs and a perceived need is fulfilled by selling something useless that is pandering: buy this gadget/product and health/beauty/sharp tools are instantly yours. Magnet therepy, herbal remedies for impotence, beauty products, and slow speed grinders are all in the same class of pandering.
When new, the slow speed grinders work great and why not? The wheels are fresh and sharp and they agressively cut while the work stays cool. You are pleased with the money spent for the problem is solved - until the wheels grow dull and then you're burning the edges again. Then you have to buy another grinder, don't you? Why not? That's how you solved the first problem with the high speed grinder.
Nope. There's good reason why grinding wheels turn as fast as they do. That's the optimum speed established almost a hundred years ago for vitrious bonded aluminum oxide grinding wheels in professional shops. You'll never find a slow speed (half speed, actually) grinder in a professional sharpening shop. They're not productive.
Times haven't changed much since 1912. The abrasive and the bond and the process controls for making grinding wheels are much more refined today but the interaction of the grain with the steel edge is still the same. 5000 to 5500 surface feet per minute is the optimum speed for aluminum oxide against hardened carbon or high speed steel.
The reason you want to buy or make a half wheel grinder is because of deliberately perpetuated ignorance and possibly because the other guys are getting them. Well, you're smarter now. Are you going to make/buy what you don't need and will work properly for a short time? Or are you going to learn dress your grinding wheels and solve the overheating problem forever?
No, you have to use a diamond dresser to make a clean smooth round sharp grinding wheel. There are no low cost options. Trust me. The wheel dress obtained by use of Norbide sticks, star dressers, the abrasive stick are all a distant second best to the silky cool cut of a sharp well dressed wheel dressed with a diamond dresser.
To answer the original question: No. There's no practical way to reconnect a 3600 RPM two pole induction motor so it runs as a 1800 RPM four pole motor.
UNQUOTE
