[Chris L]

Wayne Goddard's "The $50 Knife Shop" book talks about old electric motors from clothes dryers working well as the basis for a homemade grinder. RPMs of that type of motor I understand are the lower 1750 which makes sense for grinding metal. I've heard that 2hp rather than 1hp is ideal for a grinder.

I got this motor that's never been used (it was a replacement motor for a wood jointer).





Other than being a higher RPM motor and only 1hp, is there any cost effective way for me to use this motor for building a 2"x72" grinder? It cost me nothing, so if it would be costly to retro or modify this motor to work well, no biggie.

As you can probably tell, I know next to nothing about electric motors.

Thanks!

Chris L

[Russel Baldridge]

All you'd need is a few pulleys, pieces of steel tubing, contact wheels, nuts/bolts and a bunch of time.

I've thought about building one for about a year and a half, maybe we can have a "build off" (but I need to collect parts first).

Sorry I can't tell you much about the motor.

[Chris L]

Originally Posted by Russel Baldridge

All you'd need is a few pulleys, pieces of steel tubing, contact wheels, nuts/bolts and a bunch of time.

I've thought about building one for about a year and a half, maybe we can have a "build off" (but I need to collect parts first).

Sorry I can't tell you much about the motor.

Thanks Russel. Build off.....sounds interesting. I've been reading a bunch on building one and would probably buy the $25 plans that are out there. I'd go for the no weld tube steel approach.

My whole thing is, not knowing anything about motors, the motor I have is a fast one, and I'm afraid would simply be too darn fast for grinding blades.

Chris L

[Milton Man]

Since the belts, from what little I know, are driven by pulleys, changing the pulley diameters changes the grinder speed, very much like chaning the best on a drill press.

Sorry I can't be more help than that - maybe JoshEarl et al. will chime in.

Good luck,

Mark

[Russel Baldridge]

Yeah, if you set up a pulley system to step down the speed a little, you'd also pick up some torque which would be a real plus, when you throw a piece of steel into the grit you don't want the motor to slow down much (inconsistent grinds).

Kinda kidding about the build off, but I do need to get a belt grinder. Depends on whether I can scrounge up a suitable motor and stuff, but I think it'd be good to compare notes if we both end up making one.

[kilowattkid]

The speed seems a bit fast, but as others have stated that can be adjusted through pulley size.My question is, 'what kind of shaft do you have'. You not only need to consider the motor size and speed, but how do you apply that force to the workpiece.

BTW, Motors are precharged with smoke from the factory. If this motor smokes, you have let out all of the useful carbons. Make sure you wire it properly.

Jerry

[Chris L]

It's got a shaft that measures 5/8ths (not including the extra key like extension at the end) and is 2" long.









Chris L

[smythe]

Looks like the motor can use 110 or 220 volt AC. It’s probably wired for 110 but check the machine it was to replace because it could be wired for 220 if the wood joiner was once in a workshop… some shops use 220V for all the machines.
In that square box (with the little screw) should have wiring diagram or you will see the electrical connections indicating the wiring voltage… not much of a problem if its wired for 220 and you plug into 110 (power output will be very low) but the other way around will produce the “smoke”.

It should be easy to find a pulley with 5/8th bore and (It looks like a 3/16 inch) keyway for it. For better toque (lowest RPM) you would get the smallest diameter pulley available.

[JoshEarl]

Definitely find out if it's 220v or 110v. Running a 220v motor is more efficient, but you'll need a special outlet for it in your shop.

My grinder is running with a 1 hp, 110v motor at 1750 rpm. The 2 hp thing is good; the 3450 thing is less than ideal but you can make it work. The top speed on my grinder is 3500 surface feet per minute, which is what you'll get as a base speed if you don't try to slow it down some. That's a great speed for most grinding on steel, and I do about 90 percent of my work at this speed. You will destroy quite a few blades while you're getting the hang of it, though.

Using a step-down pulley, you can drop the speed to 1750 sfpm, or possibly even lower. The pulleys work off simple ratios. If your drive pulley is twice as big as the pulley that moves the belt, you'll double your speed. (I think you also halve your torque, but I do just fine with my 1 hp motor.) I have two step-down pulleys that work in tandem. One is on the motor's arbor, and the other is connected to to a shaft that moves the wheel that moves the belt.

The main thing you need the slower speeds for is working on scales. I sometimes wish my grinder could drop down to the 300 sfpm range for delicate work. But I haven't decided to drop $800 on a variable speed motor and control system, so I make do.

Visit www.usaknifemakers.com. Tracy has some of the best prices around, and he's extremely helpful. He stocks most of the materials you'd need to make a really nice belt grinder.

Josh

[JoshEarl]

BTW, I'm moving this to The Forge, just because it seems appropriate and I like to keep things organized.

Josh

[randydance062449]

The HP is ok and so is the motor shaft size. The speed is quite fast but step down pulleys will be necessary. What you need is a larger pulley on the grinder drive shaft and a smaller one on the motor shaft. Pulleys for the 5/8" shaft size can be a 2-3 or 4 step. The smallest beginning size step is 2", which you would want on the motor shaft. You want a 3" initial step size on the grinder drive shaft or larger. With the speed of that motor I would use a 4 step pulley system. The small pulley should be a 2-3-4-5" and the large pulley a 3-4-5-6"

Pay attention to the direction of rotation on the motor. You will want a CCW ( counter clockwise) rotation.

The groove in the shaft is called a "keyway". The pulleys will also have this. A 3/16" square, 1" long piece of mild steel is placed in the keyways to lock everything together. The pulleys should also have a set screw built in. This screws down onto the "key". I sould have my grinders here at home in a week or two. Stop by and look them over if you want to. Building them is a bit of a learning curve.

[JoshEarl]

Boy, Randy, sounds like you've been thinking about this a bit lately... Well stated.

Josh

[randydance062449]

The other major determinant of belt speed is the diameter of the belt drive wheel. Most use a 4" wheel in conjunction with a 1750 RPM motor. If that wheel size is reduced to 2" then the drive speed will be reduced by 50%. So maybe a 2" drive wheel would be the easiest way to go? Don't ask me where to get a 2" drive wheel, I don't know. Maybe Tracy Mickley does? or Rob Frink?

[Chris L]

Originally Posted by randydance062449

The other major determinant of belt speed is the diameter of the belt drive wheel. Most use a 4" wheel in conjunction with a 1750 RPM motor. If that wheel size is reduced to 2" then the drive speed will be reduced by 50%. So maybe a 2" drive wheel would be the easiest way to go? Don't ask me where to get a 2" drive wheel, I don't know. Maybe Tracy Mickley does? or Rob Frink?

Thanks for the great advice, Randy. I'll have to swing by sometime when a get a chance and see your grinders. The idea with this motor and building a grinder for myself is that the motor has never been used NOS and it was free. That said, if retrofitting this motor to make a great grinder is going to cost as much as getting a good 1750 rpm motor and twice the challenge (or hassle), then nothing lost nothing gained. I'll have to look into small drive wheels and email Tracy Mickley whom I see is also a fellow Minnesotan.

Thanks again.

Chris L

[randydance062449]

Hello Chris,

I can see how this may be giving you a sense that the motor is not worth the hassle. This is not the case. Tracy Mickley can call Rob Frink, (tracy buys his wheels from Rob) Rob can say yes or no to the 2" drive wheel. If yes, then everything becomes easy and normal. You would use the 3 step pulleys from Tracy and all will be solved. If no, then you have to jump thru some hoops to get the right pulleys for the speed reduction you are looking for.

Just one step at a time,

[Chris L]

Originally Posted by randydance062449

Hello Chris,

I can see how this may be giving you a sense that the motor is not worth the hassle. This is not the case. Tracy Mickley can call Rob Frink, (tracy buys his wheels from Rob) Rob can say yes or no to the 2" drive wheel. If yes, then everything becomes easy and normal. You would use the 3 step pulleys from Tracy and all will be solved. If no, then you have to jump thru some hoops to get the right pulleys for the speed reduction you are looking for.

Just one step at a time,

Very cool, Randy. Thanks for the reassurance and the very wise advice ("Just one step at a time"). I'll get in contact with Tracy soon and keep you posted.

Chris L

[JoshEarl]

A free 2 hp motor is nothing to sneeze at. Even a low-end 2 hp motor would probably run $150 or $200. I spent more than $100 on my 1 hp, and it's just a Grizzly motor. The two biggest expenses in building a grinder are the motor and the various wheels, especially the contact wheels.

Josh

[jbcohen]

Out of croisity do you ever use the hardware on your straights?

[barneycg]

Originally Posted by JoshEarl

A free 2 hp motor is nothing to sneeze at. Even a low-end 2 hp motor would probably run $150 or $200. I spent more than $100 on my 1 hp, and it's just a Grizzly motor. The two biggest expenses in building a grinder are the motor and the various wheels, especially the contact wheels.

Josh

On the contact wheels I've heard tell that it's possible to use polyurethane coated castors as a cheap alternative - what are your thoughts on this ?

Barney

[JoshEarl]

Shhhh... Don't let that secret out.

My 8" contact wheel came off a forklift pallet jack. Free. I got a 6" wheel on eBay for about $10 plus shipping. I got a 10" wheel for the same price.

You have to get them turned true at a machine shop, which cost me less than $50 per wheel. You could probably do better, but I live in a snooty residential area that doesn't countanance dirty stuff like junkyards and machine shops.

They work very, very well. Could a $300, precision-machined wheel do better? Probably, but I don't know that my blades will know the difference until I've had a few more years' practice.

Josh