help building belt grinder

S

sdr

Joined
Sep 6, 2015
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I'm planning on building a 2 x 72 grinder. I'm looking around the shop for parts I can use. I do have a 1.5 HP motor. Just not sure if I should plan on direct drive or step pulleys. Vfd's are out of my budget for now, however I might add one in the future. Which ever drive system I choose I'm not sure how to mount either the wheel or pully to the motor shaft. Shaft is 1/2 inch by 2 1/4 with the last half inch threaded. I'm new to the forum and not sure if this is the right place to ask newby questions or not. Any help is greatly appreciated!
 
I just built one myself, I attached a step pully to the motor shaft and a step pully to a drive shaft that had the drive wheel on the other end of the drive shaft. This drive shaft was held in place by 2 pillow block bearings. Seems to work good so far. Would definitely incorporate the step pullies, it is nice to have the variable speed option. Hope this helps.
 
Oops. I should have clarified my question. My shaft doesn't have a key way or a flat spot for a set screw. Anything I put on it now will just spin
 
Awesome, thanks. I wasn't sure if I had to grind a flat spot or make a key way.
 
I guess you could grind a little flat spot, I just used locktite and everything has stayed in place so far for me. Good luck
 
I'd grind a small flat spot for the setscrew to hold pulley.

If no VFD, then step pulley for sure - you really NEED a range of 2 or 3 speeds. Slow for sensitive grinding, and faster for profiling and heavy grinding. If you use step pulley now, it's not much hassle to change motor and add VFD at a later time if you wish.

Have fun - you'll LOVE the 2X72 grinder.

Ken H>
 
I saw a post somewhere on here that you can get a Nema 1 VFD for around $100 or something, and then put your own filters or something on it. By the time you buy the pulleys and belt you may be just as good off!

Sorry I can't help more!
 
For what it's worth I have been using a cheap vid for almost probably about 8-10 months without an issue. It was $100 and it's been working fine. For the last 2 months it's been pulling double duty powering my disc and belt. I personally knew I'd never change speed with step pulleys and needed the variable speed. I did not build an enclosure for it and neither motor I am using are sealed. The vfd is mounted under the bench and I blow it out with compressed air about once a week. Just my $.02. I know this post will be frowned upon and looked at as bad advice but you gotta do what you gotta do when you're broke.

Link to my build
http://www.bladeforums.com/forums/showthread.php/1244694-Eerf-grinder-build-a-long
 
Kevin Powers said:
For what it's worth I have been using a cheap vid for almost probably about 8-10 months without an issue. It was $100 and it's been working fine. For the last 2 months it's been pulling double duty powering my disc and belt. I personally knew I'd never change speed with step pulleys and needed the variable speed. I did not build an enclosure for it and neither motor I am using are sealed. The vfd is mounted under the bench and I blow it out with compressed air about once a week. Just my $.02. I know this post will be frowned upon and looked at as bad advice but you gotta do what you gotta do when you're broke.

Link to my build
http://www.bladeforums.com/forums/showthread.php/1244694-Eerf-grinder-build-a-long
Click to expand...

If money is really that tight Kevin has some practical tips. As far as using open motors, I have a couple that I have bought used and used like heck on and off over the years depending on how many and what Belt & disc I am currently running in my shop.

Do NOT use an open motor for any wet grinding!!!.:eek: If you have a compressor in the shop just blow the swartz/dust out of any open motors or controllers at the end of each day.

To use a step pulley system. I put the motor on a hinged board with link belt to adjust the tension. I purchased one of these Coote grinder over 16 years ago and its still working great . here's a pic of a hinged set up.
http://www.cootebeltgrinder.com/motor_setup.html
 
Thanks for the advice guys, I would rather do a vfd. Modifying one doesn't bother me as long as the price is good. I'm on a small budget with this project. Mounting the drive wheel is a mystery to me. My motor shaft is 1/2 by 1 and 3/4 long. I assume a wheel fits that? Wish I could figure out how to post pics from my tablet. I did read some info about posting pics but started getting brain damage
 
As long as you can get an inch 'n half inside the drive wheel you'll be just fine. Main thing is to have the set screw well on the shaft.

On the VFD, that will require a 3 ph motor. A 2 hp, 3 ph motor is $127 shipped for a 3450 rpm, and 3 hp Chinese VFD (NEMA 1) is around $116 shipped. You will be VERY happy if you go VFD route. TECO NEMA 4 is a GREAT VFD, but just a bit pricey for me as a hobby user.

Ken H>
 
Wow, even more brain damage! After reading many posts I'm needing more help deciding on the right motor. It sounds like I should just go with the variable motor and forget the step pulleys. Buying new is not an option for me right now. Sooo... I'm wondering if one of my treadmill motors is a good option for me. I'm not too worried about mounting them, they seem easy enough to get right. I don't have a DC controller but it doesn't seem hard to find one. Making a filter does seem important though. The 2 motors I have are; 90vdc, 15 amp, 4800 rpm. 120vdc, 5600 rpm, 2.5 HP. Do these sound ok? In the future upgrading the motor may be possible cost wise. But for now free and cheap are what I'm aiming for. Thanks again for the help

Ken your 2 x 72 is incredible!
 
Find a surplus yard. I have had very good luck getting motors at my local yard. One was brand new. At first I was tempted to build a grinder halfassed(I still kinda did). I'm so glad I didn't. Get a 3 phase 3450 motor and a vfd and call it a day. You'll be much happier in the long run. Forget treadmill motors and skateboard wheels and get the right stuff for the job.
 
Here's a thread I previously did on converting a 4x36 belt sander into a 2x72 grinder. While it doesn't address the issues you're currently pondering, you'll eventually get to the point of building a platen and I wanted to help you save money. Specifically about using a $25 caster as an 8" wheel. Unfortunately, Northern no longer carries the casters I used in the thread, but I recently bought a new one from Menards. It is polyurethane cast around steel and will need a good bit of balancing, but is very true and grinds nicely, being the same 70a durometer as most $125 grinding wheels. On tool arm setup, it is very easy to bolt one on to the 1.5" arm. I know the picture shows a plastic hub, but the ones I've found in the store are steel. Once you put the bearings in, put a bolt through it and the heavy side will roll to the bottom. Drill holes in heavy side until it doesn't roll to the bottom anymore. I have to drill around 15 1/2" holes in the last one, but it is balanced perfectly now and grinds excellently.

http://www.bladeforums.com/forums/showthread.php/803811-DIY-4x36-into-a-2x72-grinder-conversion
2176055.jpg
 
sdr said:
Sooo... I'm wondering if one of my treadmill motors is a good option for me. I'm not too worried about mounting them, they seem easy enough to get right. I don't have a DC controller but it doesn't seem hard to find one. Making a filter does seem important though. The 2 motors I have are; 90vdc, 15 amp, 4800 rpm. 120vdc, 5600 rpm, 2.5 HP. Do these sound ok? In the future upgrading the motor may be possible cost wise. But for now free and cheap are what I'm aiming for. Thanks again for the help
Click to expand...

If you already have a treadmill motor, go with it. I've converted lathes with AC motors over to DC using treadmill motors. There is no reason you should need to upgrade in the future. Buy an MC60 controller, they are the most common and the wiring is simple. Although it might be simpler to buy a used treadmill and strip it down so you'll have all the electronics. Older treadmills are better, simpler. Matter of fact, I will be starting a 2x72 grinder this fall and already have a dc motor with electronics for it.
 
I have 2 older treadmill motors just no controller. I found a free treadmill on craigslist I'm checking out tomorrow. I was planning on using caster wheels. I found a lot on eBay. Most with bearings. Some are shaped like tracking wheels. I may run into a problem finding a drive wheel for the motor shaft. That will be the next problem to solve.
 
sdr said:
I have 2 older treadmill motors just no controller. I found a free treadmill on craigslist I'm checking out tomorrow. I was planning on using caster wheels. I found a lot on eBay. Most with bearings. Some are shaped like tracking wheels. I may run into a problem finding a drive wheel for the motor shaft. That will be the next problem to solve.
Click to expand...

Yeah, if it's one of those that run flat belts they are a pain. The smartest thing is probably just to remove the flywheel, they usually screw on, and if you reverse the motor they will sometimes just spin right off. The motor for my grinder has a flat belt pulley and I haven't decided yet whether to remove it (it's part of the flywheel) or make an adapter so I can run a V belt and keep the flywheel. If you salvage another treadmill there are usually a lot of extra electronics you don't need. The important parts are the motor (obviously), the choke (a transformer between the motor and controller), and the PWM. Old treadmills may already have a potentiometer but usually they are digital. Don't throw any electronics away until you have the motor running outside the machine.
 
Both my motors have just the shaft. The biggest motor is a 5/8 shaft. The smallest is 11/16
 
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