coote grinder motor question

sunny_2_75

sunny_2_75

Joined
Nov 23, 2009
Messages
71
Hello everyone, just got my coote grinder. Now looking for a motor. The recommended motor that Norm suggested was a 1hp that runs 1750rpm's. Having problems finding a used motor that runs 1750rpm's. Im working on a tight budget. I have a 1hp motor that runs 3450. Is there a pully set up that i can use that will reduce the speed for a ten inch wheel set up.
 
pretty much just have to halve whatever else you'd be using, I think. Or use a jackshaft.

for a jackshaft, get two pillow block bearings, and 4 3 or 4 step cone pulleys. put one step cone on the motor, one matching on the jackshaft, another on the jackshaft oriented for the grinder, and then one on the grinder. It will look odd if you aren't familiar with old lathes and tooling, but it used to be a pretty common way to get more variable speeds. And it works. I have a jackshaft on two lathes, and am about to convert my coote to that, since even with a 1750rpm motor and cone step pulleys, I want to have a bit more speed control


honestly, this isn't going to cost a lot more (usaknifemaker has all the parts) than buying a 2.5 inch and an 8 inch pulley wheel.
 
I think i get what your saying...really not all to familiar with that king of stuff. I will get on US Knifemakers and check out the parts. If i did have the motor Norm recomends do I just run two three step pulleys? He didnt mention any recomendations.
 
half the pulley size on your motor..4" pulley on the grinder and a 2" pulley on the motor will give you 1725 rpm with a 3450 rpm motor..
 
Is this a good speed to run for just a single speed operation till i get something else? I will just be practicing on mild still for now.
 
1725 will be fine for now. We ran our coote with a 3450 motor half speed like that for about three years. Sometimes we just have to make the best with what we have to work with :)
 
Hi Sunny - I'd just like to suggest starting out with a three or four pulley setup out the gate. It probably won't add 20 dollars to your setup and will give you variable speed

Edit to add - I don't know what pulley's Tracey has available, but if he doesn't have step pulleys, they will be easy to find online.
 
if doing a single pulley, I'd suggest running the 6 inch or 8 inch and 2.5 - going a bit slower is better.

but tracy has the step pulleys on the website with the no weld grinder supplies. you can add the jackshaft later, too.
 
Thanks for all the replies on this issue. I think I have enough info to get started wich is ultimately what I am after. Thanks again to all who replied. I continually go to blade forums for information and have never been let down.
 
Check out this this thread. 4- usable speeds for a Coote with one step pulley..
http://www.bladeforums.com/forums/showthread.php?t=830233&highlight=pulley
You cant really use two step pulleys for a coote with a 3450 rpm motor, well you can but most of them will be unusable..Remember a 10" coote is only good to 2000 rpm's..Even with a 1725 rpm motor and step pulleys one of the speed will be usless with a coote, much too fast..
Say you have 4 step pulleys. 2" 3" 4" 5"
Heres your speeds. @1725 rpm
Drive pulley............Driven pulley....RPM's
2"------------------5"------------690
3"------------------4"------------1293
4"------------------3"------------2299
5"------------------2"------------4312
Heres some more...Single pulley speeds.
2.5"----------------8"-------------538*
2.5-----------------6-------------717*
2.5-----------------5"------------862*..These three are pretty slow for any hard stock removal but good for finsihing..
2.5-----------------4"------------1078
2.5-----------------3"------------1436
See what I mean, two of the speeds are pretty much usless on a 10" coote..You'll have one usless speed on three step pulleys.. Ive been using a Coote for a while, trust me you dont want to get much over 2000 rpm's on a Coote..It screams for mercy..Too much for a two wheel grinder and a 10" wheel..
.
Heres the formula for Sq. Ft. per minute if your curious..
Motor RPM X motor pulley diameter divided by driven pulley diameter X band wheel diameter X 3.1416 divided by 12 = SFPM
 
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awesome post!

This is where the jackshaft comes in. once you get 2 more step pulleys and pillow blocks, you have ways to get down into the 200 range, and lots of choices below 1600

my experience, which is NOT normal, since I do a lot of convex work, is that I really get the most out of the 400-900sfpm ranges. the high speeds are wonderful for profiling. So looking at usage might matter, too.

Note that doubling for 3450 rpm, the 2.5 and 8 inch pulleys are right up in a usable range.

Oh, also, you can do a jackshaft with a 2.5 inch pulley on the motor and a 6" on the jackshaft and all the step pulleys become usable. That's a bit easier.
 
I built a coote grinder too, mine has the 6" wheel. I found a motor (I think 2 or 2.5hp Baldor) on ebay that has the right speed for the shaft and went direct drive with a vibration dampening connector (can't remember right name any more)

One way you can do it is mount the motor behind or below the grinder, in the linked page the guy had a very nice setup where you lifted the motor and slid it to move the belt on the pulley, then the weight of the motor tensioned the belt. He mentioned having a spring in many cases. I have some pics and information somewhere but it's been years and I couldn't find it now. Anyways, if you mount the motor below, you don't need anything fancy, a simple plate hinged on one side is sufficient (Imagine the grinder at work height and the motor down about shin/knee height).

You can have a slot in the plate, run a bolt from a lower brace/mount through the slot and use a wing nut to tension it, put a spring below the plate, on/around the bolt, and you have resistance to the plate just falling (if you want, but not necessary I don't think).

These were things I considered when building mine. In the end because I use it for non-delicate work (I'm not knife maker) I just went with a single speed setup. Where I live there is a local "bearing" place, they also carry or can get all the pillow blocks, step pulleys and jack shafts you need, maybe you have similar where you are?

Red
 
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