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Thread: Belt-driven Bench Grinder???
11-30-2008, 01:20 AM #1
Belt-driven Bench Grinder???
So I have a motor I am looking for a use for and have some questions.
- Baldor - 2 HP
- 115/220 VAC
- 1725 RPM
- 1.125" diameter shaft
I was thinking of maybe building a belt-driven bench grinder (my factory-built one is just about dead). Is ths a good idea, or does something like this not work as well as a factory-built unit? I know I would need to offset the pulley sizes to achieve a faster RPM on the grinder, but that should be easy enough to do.
So, has anyone done this before? Are there pictures / specs you could share? Or any other suggestions for the motor?
11-30-2008, 03:24 AM #2
Belt driven Bench Grinder
I recall that the late Kenneth C Hart writing as Martin Cleeve in Model Engineer published the design for his in the early 1950's.
Shortly before his death, Cleeve published 'Screwcutting in the Lathe' and although it is difficult to see, the belt driven grinder is the tool for his ideas of sharpening his HSS Vee tools.
Maybe someone else has the old Model Engineers which give the details but we had to drop the ideas of putting this stuff on the web by the new owners of the magazine.
I hope that this is some use to you
11-30-2008, 04:48 AM #3
Hell yes, makes a lot of sense. A little pulley in the middle and a couple of ball bearing pillow blocks, a double ender shaft, motor below, V-belt between. Mount it all on a plate and make a nice sturdy easily adjusted tool rest for it.
11-30-2008, 05:41 AM #4
General Tool used to sell Grinder/Buffer heads that were belt driven. Basically a one piece Zamac Casting with two pillow blocks in the expensive one and plain bushings in the cheap one. Sometimes it also had a pulley guard as well. I have one of the better ones that they made for Sears that says Craftsman on the front. Think I have another one with only the bushings still in the plastic bag. Cost around $10.00 or less when I bought it 20 years ago. The only issue is changing the drive belt and if you use a poly twist belt then it is not a problem at all.
11-30-2008, 05:44 AM #5
Belt Driven Grinders
A 'Senior Moment'- sorry!
The book 'the Grinding Machine' by Ian Bradley- ISBM 0 85242 324 1
(MAP) has a a whole chapter devoted to all sorts of belt driven stuff.
Well worth the efforts to try and get a secondhand copy!
11-30-2008, 05:50 AM #6
Don't forget, if you make your own shaft, the right hand side side needs to have left-hand threads!
11-30-2008, 05:56 AM #7
My belt grinder is belt driven (and I don't mean the abrasive being the drive belt).
Separate motor for a bench grinder sounds like a great idea since all the retail ones I've used of recent manufacture are incredibly easy to stall (borderline worthless - and we're not talking about low end import crap). I have a taiwan 1/2hp 6" that I can stall grinding grooving tools out of HSS blanks (FIL gave it to me), but my 3/4hp 8" isn't much better.
Another benefit is that you'll have less "bulk" between the wheels for more clearance when doing contours.
11-30-2008, 06:57 AM #8
1725 R. P. M. may be a little slow for a direct drive grinder. A 3450 R. P. M. motor would be better.
11-30-2008, 10:55 AM #9
I have one that I built long ago, using pillow blocks as mentioned before. It works great.
I do, however, have a feeling that if I ever hire an employee, my grinder will have to disappear, as there is no satisfactory way of guarding it and it will not fly with an OSHA inspector.
11-30-2008, 11:12 AM #10
Your idea is a great one...but I'd add this. 2hp could make one heck of a grinder!
You might want to save th 2hp motor for something else and buy an inexpensive 1/2hp for this purpose...but its not a requirement.
I'd say that you need to balance the shaft size with the distance to the bearing support. IOW, you can't copy the scale of a belt-driven buffer which might have 8" between the wheel and the bearing support.
This is a 3hp grinder for comparison. It doesn't use wheels, it uses *rocks*
11-30-2008, 02:09 PM #11
The matter of motor speed, grinder speed and motor power has to be related to the size of the grinding wheel. Big wheels can use lower speeds and more power. Little wheels need high speeds and low power. If the plan is to use the 2HP 1750 motor to its full potential, then pick the wheel size first. I would prefer a TEFC motor for a grinder, but you might just shield an ODP motor from the grit you make.
I like to let experienced professionals do my design work whenever possible. So I just went to the Baldor web site and clicked up their 2HP grinders. They have a single phase model 1217W with a 2HP 1800 RPM (nominal, really 1725 or so at rated power) motor. It uses 12" x 2" x 1 1/4" wheels. So there you are: design done. You might lose a tiny bit of power in the belt efficiency, but I would just use a 1:1 pulley ratio. You can probably build a really great grinder for a lot less than the $1850-$1900 price of the Baldor 1217W. You can buy parts like the eye shields from Baldor, or on eBay.
And the RH thread goes on the right side and the LH thread goes on the left side of the spindle. The idea is to make wheel slip, if any, tighten the nuts.
11-30-2008, 02:49 PM #12
LVanice is right. If you don't do you homework you might make a bomb, not grinder. Wheel speed can directly affect your lifespan.
11-30-2008, 02:56 PM #13
The first bench grinders were all belt drive, this is not unexplored territory and can be made to work just fine.
Here's a thread in the antique machinery forum I started trying to find the maker of one I just aqquired, it has a pic or two if that helps.
Mine is flat belt but the design would be easily converted to vee belt
Flat belt Bench Grinder
11-30-2008, 04:31 PM #14
I earlier wrote, "Don't forget, if you make your own shaft, the right hand side side needs to have left-hand threads!" which is wrong. L Vanice's post is correct. Sorry about that.
11-30-2008, 05:21 PM #15
If you had an issue with the belt slipping, you could just use double belts like an air compressor. My lathe spindle is actually belt driven by 5 v-belts from the speed gear box, the geared head is then driven off the spindle.
11-30-2008, 07:43 PM #16
As stated been done that way before electric motors existed. Her eis a link to a rock grinder set up. about four seperate wheels on one belt driven shaft. No idea how you change wheels or belts, probably takes some time for the inboard wheels.
Easy way to make a grinder is to
use you existing one. either put a pulley on one end or mount a pulley where the rotor was on the old shaft. then cut some slots to let the belt go inside the motor casing and out to the new motor. If nothing else I would see if you can reuse the motor shaft and guards with a pillow block set up.
11-30-2008, 07:48 PM #17
I've used belt-driven grinders for fifty years. One 8" Dayton unit I bought from Grainger thirty-five years ago, driven by a 3/4hp motor, is still in use today, just replaced the bearings this year. Properly designed, they have advantages over direct drive grinders. One is the body of the motor is not in the path of long work. Also, the shaft can be made any length. This is advantageous if you might ever want to use it as a buffer.
For your 2hp motor, I'd make the 1" shaft about 24" long, with the pillow blocks about 12" apart and the pulley between them, mounted on the heaviest stand I could devise. The base on one of mine is a 24"square of 1/2" steel plate. Make the rests and guards removable, so when it is to be used as a buffer, there is 360-degree access to the buffing wheel.
thnx, jack vines
12-01-2008, 12:20 PM #18
I have made and used quite a few belt driven wheels. My mother has a friend who's father was killed by a grinding wheel coming apart and hitting him square in the head. It does actually happen. I had a grinder set up that did not have guards on it. I really like this setup because I had a vapor zone set up on it that used a 50/50 mix of detergent and water. It is really stingy on coolant and the only time you can tell there is vapor there is if you stick your finger up near the wheel and then it comes away wet. I use it for grinding anything that I don't want to overheat. I got scared when I heard about this guy getting whacked so I made some guards out of brake drums with a segment cut out with a torch. I think they will stop the wheel if it splits or at least deflect it. You may want to do this Rockfish.
12-01-2008, 01:18 PM #19
12-01-2008, 01:45 PM #20
Belt driven grinder
Have a look at this link for a four wheel grinder,
If it doesn't work go to Google. type: Britan Grinder & then search in "images"