belt sander

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jraney

Joined
Aug 6, 2010
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hey i might have missed this but what is the purpose of having a variable speed steup? i have an electric motor that i was going to use to biuld a sander is it possible to wirein a dimmer switch to control my speed. i have been told that this could burn up my motor if it is not a 3 phase motor, so i figured i would ask you folks.

josh
 
I think most people would agree sometimes you want to hog off a whole lot of metal really fast, so higher speed is better; when you want to go slow and careful, lower speed rules. More control at lower speed. Variable speeds can be acheieved by a 3-phase motor wired up with a switch or pedal, or any motor driving pulleys of varying diameters. Generally a popular set-up is a 3450 RPM motor with a 4" drive wheel, good single-speed choice. That's what I'm setting up now. Next grinder I make will be 3-phase with a pedal.
 
ok so what am i in for ? is this going to be really hard to biuld or are most of the parts i need easy to come by or what? so the main thing you think is the rpms of my motor?
so about all the question but when facing a file to cut the entire bevels anything has got to be better, don't get me wrong if that is what it takes then that is the way i will do it but it is going to take awhile.

thanks
josh
 
For true variable speed, you need a VFD, Variable Frequency Drive and a 3 phase motor.
Search here for VFD will give you hundreds of threads.

Variable speed gives you control and means you make your mistakes much more slowly.

A dimmer switch on these motors will give you smoke.
 
jraney said:
ok so what am i in for ? is this going to be really hard to biuld or are most of the parts i need easy to come by or what? so the main thing you think is the rpms of my motor?
so about all the question but when facing a file to cut the entire bevels anything has got to be better, don't get me wrong if that is what it takes then that is the way i will do it but it is going to take awhile.

thanks
josh
Click to expand...

No it's not hard to build, but it's not a 5-minute project. IMHO the best option for a home-built grinder is the Grinder-In-A-Box kit from Polar Bear Forge, which consists of the frame components laser cut from 1/2" steel. You'll need to drill and countersink a few holes, tap some threads. you'll have to scrounge up some angle iron for a tooling arm, and acquire wheels. You can order a new motor for it, or scrounge up a used one somewhere.

If you haveaccess to a sheet of steel, you could cut the pieces yourself, but most people wouldn't be able to save money doing that over buying the kit. Jamie ought to get a Nobel pize for putting that kit together.

If you're handy with welding, you can make the frame from angle iron.
 
is the motor i have good for anything? i will look at it tommorow but i think it is only 1/3 hp if that makes a difference. well i will check out the grinder in a box deal anyhow.

thanks
josh
 
1/3 Hp would be on the lower end of the small side for a 2X72. Most people are going 1-3hp for their grinders.
 
oh well i found the motor anyhow thought i might get lucky and be able to use it for something like this, looks like i will need another plan of attack.

thanks for the info better now then later and me asking why it didn't work.

josh
 
I am in the midst of collecting the parts to build one of the Grinder in a Box kits, I plan on going with a VFD and that is my stumbling block. I am having a heck of a time picking out a VFD that suits my needs, 110V input 1.5 Hp rating and a reasonable price for the home hobbyist. Not many manufacturers make 1.5 Hp 110V VFDs and they are all on the pricey side if I end up having to buy a new motor. If this keeps up I may have to break down and go the single phase and step pulley route.
 
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