Coote grinders

[grizzled gizzard]

Hello gentlemen, I'm going to pick up a Coote grinder very soon, and I need some advice.

First of all, I'm getting the 2x72 because it seems so much more popular. I'm guessing it's more economical (more belt for the money), and helps dissipate heat better. Is that close? Other than not taking up as much space, is the 2x48 better at anything?

I'm going with the 10" wheel because I figure less hollow-ground is better. Are there other concerns I need to be aware of? Would a smaller wheel be better for other things?

Now about the motor... I have a 3hp, 3phase Marathon motor that needs a variable frequency drive, but there are really a wide range of VFDs, and the prices are way different, and I'm just talking about ones that should match my motor! This is my main question. What sort of VFD do I need?

Any info is more than greatly appreciated.

Thanks a bunch,
GG

 

[Justin.Mercier]

to get the proper VFD for a 3hp motor, you're looking at a lot of money, more money than you'll be spending on the coote grinder.

 

[tattooedfreak]

Wow.. a 3hp. I run a 1/2 hp on my coote (yes it bogs occasionally) I will upgrade to a 1hp in a few months but it works for now. I use step pullys for speed changes and it works fine. With the coote, make sure you have room behind it so you can swing the upright back for hollow grind. You will find that the pulley side will get in the way sometimes but you learn to work around it. I have both the 10" and 6" wheels but I dont use the 6" that much as it's a pain to raise the upright when you switch out the wheel. It all depends on what im working on. You can use the 10 for hollow grind, put the platten on for flat or leave the platten on and use the wheel for a semi hollow (you'll see when you do it). It's a great machine though and belt changing is simple and quick. Once you get used to it, you will see that it is a very versitile machine.

 

[Justin King]

The 10" model with a small wheel attatchment is probably the moste versatile Coote setup, IMO. The only reason to go with a smaller contact wheel would be if you want a specific size of hollow grind. Personally I don't care much for hollow grinds and if I did them it would be on a 10" wheel or larger.

 

[travis wuertz]

I really like KB electronics vfds. For 3hp you will need a KBAC 29D. It will do 3 hp and will cost you probably in the neighborhood of $300. I also recommend State Electric, I've used them for a lot of motors and controllers.

On another note anyone thinking of buying motors, new motors as of Dec 12, 2010, motors produced or imported to the US will have to be "premium efficiency" meaning 84.5% and higher instead of the usual 82.5% (approx). No big deal for buyin used stuff, but I just thought I'd throw that out there. Thanks government.

Also I beleive I saw in Surplus Center, surpluscenter.com some VFD controls. They weren't totally enclosed, but I imagine a do-it-yourselfer could make it work. I remember them being pretty cheap. Check out surplus center anyway they got all kinds of cool stuff.

 

[C_Claycomb]

I have the 10" wheel and often wish I had gone with the 8". I don't do hollow grinds, that might change, but so far everything I do is flat and even a 10" wheel doesn't give as broad a hollow as I would want on most of my knives.

What can an 8" do that a 10" can't? Handles and tang tapering.

The smaller wheel will let you hollow material from the center of a tang, prior to flattening, with greater precision and safety than the 10". You can't grind all that deeply into the tang before the grind runs off the edge with the bigger wheel.

I like to do sculpted handles. There is a series of photos of me working on a Spyderco bushcraft type handle to show what I normally do. An 8" wheel is just right for hogging material off a handle and leaving the shape that I like. The 10" wheel ist too big for handle sculpting. Sure, you can hog some material off, but agian, it is easy to go too far because of the larger diameter.

Other factors. The 10" does allow me to fit the 9" disc and while the disc is great, 9" is really on the borderline. A 12" would work much better and if I had the space I would be happier like that. The disk can also get in the way when profiling on the "knife maker's rest" against the wheel.

The 10" wheel comes very close to the bench top unless you put a spacer under the base. Close enough that you will probably struggle to get a Scothbrite belt fitted if you don't raise the base a bit.

Cant' comment on the motor. I have a 2hp motor and it works very well. The Power Twist belt was a great buy to reduce vibration and it pays to take care on how you set up your pulleys to ensure they are really tight and concentric on the shaft.

Chris