ready to purchase first 2x72 grinder, coote, grinder in a box, other?

M

mxlj

Well-Known Member
Im getting ready to purchase my first 2x72 grinder. I have been looking at a coote grinder and the grinder in a box from polarbear forge, or any others out there that anyone recommends? Ideas, Pro's/cons' to each one? I am trying to stay under a grand for budget. Any good used one for sale that need new home also, let me know.
I have been using a 1x30 HF and 4x36 HF for the last year, so any grinder will be a big upgrade. I was looking at the kalamzoo but seen the coote was more recommended. Plus you use step pulleys on it. Now with the grinder in the box is it direct drive. I may or may not be buying a VFD.
What motor speeds are recommended for a 3 step pulley set up? or the direct drive style? Does it matter on the direct drive if you are going to be using a VFD or not? thank you, Larry
 
The people who make the Coote told me that I would have to keep the motor speed to around 1700-1800rpm if I wanted to use a three step pulley cone with my grinder.

Doug Lester
 
I built a NWGS for my first grinder, and I think I currently have between 6 and 700 bucks in it all together. That includes the following:

8" contact wheel
Flat platen that converts to a slack belt
Small wheel attachment
Tool table
1.5 HP motor (bought used for $80)
3 step pulley

My motor is 1725 RPM as well, and it seems to work quite well with a standard 3 step.

If you want to go with a VFD, be prepared to spend AT LEAST 500 bucks for 1.5 HP or greater. For a quality VFD you can easily spend upwards of $800 to $1200 or more without even trying.
 
I'm putting one of those types of (grinder in a box) grinders together right now. The biggest flaw I have found is the belt tension....a tension spring is simply NOT the way to go. I'm in the process of building parts to make the belt tension a compression spring (similar to what the KMG uses). The problem with the tension spring belt tension is that it does not keep the belt tight enough, and as a result, tracking suffers. To explain...the tension spring will let the machine track just fine, until you start putting pressure on the grinding surface...then the belt will sometimes "walk" or "jump"...that's a sure sign that the belt tension is not sufficient. I have to emphasis that the one I'm working on is NOT from Polar Bear forge.....but is identical. I've also had to shim up the idler wheel block to eliminate "play". I will also be building a shaft for the idler arm to frame connection...using a 1/2" bolt is too sloppy for my likes.

My intent is to buy a motor and VFD from Wayne Coe when I get that far.

This type of grinder only confirms what I have always told folks about purchasing grinders....what you pay for in the "top end" grinders is the precision. This grinder will be fine for my intended use...as a grinder for my blacksmith shop, but I would never be satisfied with it as my primary grinder. I suppose you could say that I've been spoiled after having used the "top end" grinders, but once you work with one of those machines, settling for anything less is hard to do.
 
Last edited:
If you decide to build and go with variable speed, check with Wayne Coe for prices on motor and VFD. In my research, I find he has the best prices.
 
I have a Coote and its not bad but honestly if I could go back and do it all over again I would get a bare bones KMG package with possible one small wheel attachment. You can add on on along the way.
 
Ed Maybe you are not using a strong enough spring. I use a 13/16" X 4" X .120" spring that I get from Lowes or Home Depot. Sometimes I wonder if I am not getting my belts to tight.

Larry, I sell the 1.5 hp motor for $225.32 and the KBAC 27D VFD for $375.00 both with free shipping CONUS so much cheaper than what was quoted above.

You will get a much more versitile grinder with the GIB than the Coote. You can get Jamie's rotating tool arm and mount 8" and 2" wheels and have the slack belt and flat platten all on one tool arm.
 
The Coote is a well built grinder for the money. However, it is not very versatile. It is what I have currently and would recommend the GIB or KMG basic if you can afford it.
 
I would buy a flat platen KMG from Rob for 750,get a motor and controller from Wayne.You will have the best starter package out there IMHO.Then you can add pieces to the KMG as your buget allows.
Stan
 
While I will admit that I am biased a little bit, I do believe that all the grinders listed have a place depending on each person's criteria.

Ed, for tension, I've always used tension springs. The first grinder I built was many, many years ago, and that's what I used. There was a design or two I tried a few years back that I used a compression spring, but otherwise all my grinders have been tension. The only time I've had belt drift problems, it was caused by a wheel. I'd be curious to see the changes to make to use a compression spring, if you'd be willing to share. I've seen a couple other variations that people have used to accomplish the same thing.

Regardless of which one you decide on, go to Wayne to get your motor and controls.

Jamie
 
thank you for the info guys. I am ready to buy right now, but i may have to think on it a bit longer and decide - kmg, coote, or nwg, GIB.
 
Wayne Coe said:
You can get Jamie's rotating tool arm and mount 8" and 2" wheels and have the slack belt and flat platten all on one tool arm.
Click to expand...

Did you have a post or link for this? i did a search and it didn't come up with anything but your post in this thread.
 
Well I might as well throw in my two cents worth. Being the ultra cheep person that I am I bought a Coote with a ten inch wheel and liked it so much that I got a second one with the small wheel add on and I love them. That being said I have to say that I don't mind making any attachments that I might need.
 
EdCaffreyMS said:
The problem with the tension spring belt tension is that it does not keep the belt tight enough, and as a result, tracking suffers. To explain...the tension spring will let the machine track just fine, until you start putting pressure on the grinding surface...then the belt will sometimes "walk" or "jump"...that's a sure sign that the belt tension is not sufficient.
Click to expand...

I had that problem with the tension spring on the no-weld grinder I built. The tension springs I found locally didn't provide enough tension and the belt would wander. So what I did was just use two springs...it solved the problem. It actually turned out to be a little too tight so I stretched the 2nd spring a bit.

I kind of like it the way it is now. I use 2 springs for most of my grinding but I can switch back to 1 spring if I want a very loose slack belt.
 
I built the Polar Bear Forge GIB. I am very happy with it. I wanted variable speed after comparing my friend's variable speed KMG to his single speed Grizzly. If you have an unlimited budget, want variable speed and to start grinding right away go with the KMG. But I'm a bit on the cheap side and wanted to spread the expenses over time. I also thought if I couldn't make the kit, I was kidding myself thinking I was going to make a decent knife. At the end of the day, not counting misc. tools, taps, bits and wrong hardware purchases,etc., I have about $1,100.00 into mine. This includes good components- Baldor motor, KBAC 27 vfd, Beaumont 10' contact wheel, drive wheel, platen and wheels. It was a project for me since I'd never drilled a hole exactly where I wanted, let alone used a tap. But the kit is forgiving and completing it was satisfying. Jamie was very helpful whenever I had questions along the way.
 
It might not make sense, but I'm convinced that you could put a tension spring on a grinder that is so strong that a single person could not release the belt, and still it would not work as well as a compression spring located in the correct position. It's not about how strong or weak the spring is, it's about leverage. As it applies to an idler arm on a grinder, the tension spring is always located on the "short end" of the leverage and simply does not provide "positive leverage" (for lack of a better term) or "strength" of pressure on the belt that a compression spring does. While a tension spring may "work fine" for some, I would venture to say that if you had two of these machines, one with a tension spring, and the other with a compression spring, there will be a noticeable difference in favor of the one with the compression spring in terms of tracking and belt drift during use.

Once I get the grinder finished up, I'll make sure I get some pics and post them. In words, what I did was drill/tap a 3/8-16 hole in the portion of the grinder that holds the tooling arm. I then machined out an adjustable stop for the bottom of the spring. The contact point for the top of the spring is just forward of the tracking adjustment threaded hole on the idler arm.
 
You must log in or register to reply here.
Back
Top