Grinder build question - possible to start on single speed and later upgrade to VFD?

L

leozinho

Member
Hi all,

I'm researching my grinder build. I plan on purchasing the GIB from Polar Bear Forge. I want to use the multiplaten with contact wheels.

As most of you probably know, the GIB is direct drive (no step pulleys).

To keep my initial costs down, is it possible to use a single speed motor that can later be upgraded to a VFD? (Do only certain electrical motors work this way, ie they are one set speed unless you hook up a VFD, and then they are variable?)

If so, what RPM motor should I consider, and what size drive wheel to give me a usable belt speed.

(Right now I'm using the Craftsman 2x42 and definitely know that it is running to fast.)

Thanks for reading my newbie question. I see a lot of people talking about step pulleys to keep cost down on KMG clones, but that doesn't really work for the GIB.
 
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I built a GIB and I think you've made a good choice. To use a VFD you'll need a three phase motor. My understanding is that if you want use a three phase motor you can't just plug it into household receptacles. You'll need a converter. Once you buy that you might as well get a VFD. I think the KB Genesis is the best. I can't remember the model number but it's the one with the NEMA 4 case. May seem pricey at $400 or so with shipping. But you can install it yourself and it's flexible. Any three phase motor up to 2 hp. I bought a 1 1/2 hp 3400 rpm Baldor, new surplus on ebay. But I've heard others say get a 1750 rpm then set the jumper on the VFD to double speed.
But, if you decide to start with a single phase single speed motor, I talked to the guy who designed the EERF grinder that the GIB is based upon. He said because it's direct drive get a 3000 something rpm motor and not less that 1 1/2 hp.

Good luck and have fun with the build.

Jay
 
You will have to use a single phase motor (unless you have 3 phase available) unless you use a VFD then you will need a 3 phase motor. If you get a single phase motor you should get a 3600 rpm TEFC motor. If you do start off with a single speed grinder and you are making knives it will be a short time before you will be wishing that you had the variable speed available with a VFD, then not only will you need to buy the VFD you will have to buy the motor too.

I have about the best prices around for motors and VFDs as well as support for any questions. I have a wiring kit that includes everything you need to hook up the motor and VFD and purpose specific instructions.

The GIB is good choice and Jamie is a good guy to do business with.

Let me know if I can help you.
 
leozinho said:
Hi all,

I'm researching my grinder build. I plan on purchasing the GIB from Polar Bear Forge. I want to use the multiplaten with contact wheels.

As most of you probably know, the GIB is direct drive (no step pulleys).

To keep my initial costs down, is it possible to use a single speed motor that can later be upgraded to a VFD? (Do only certain electrical motors work this way, ie they are one set speed unless you hook up a VFD, and then they are variable?)

If so, what RPM motor should I consider, and what size drive wheel to give me a usable belt speed.

(Right now I'm using the Craftsman 2x42 and definitely know that it is running to fast.)

Thanks for reading my newbie question. I see a lot of people talking about step pulleys to keep cost down on KMG clones, but that doesn't really work for the GIB.
Click to expand...

I suggest you go with Wayne Coe's advise and I would get at least a 1 1/2 HP motor. You will have buyers remorse soon if you get that cheap 1HP and controller.

Only cry once! Get a 1 1/2 or 2HP motor and be done with it!

Laurence

www.rhinoknives.com
 
I forgot to ask an important question. Do you have a experience in electric and mechanical repair? if you do, shop the web, you can find top quality brand new motors and phase convertors/variable frequency drives for not much money. BUT you have to do all the wiring and setup yourself. 1 wire out of place and you will let all the smoke out of your pieces. If you do not have electric repair backround, buy from someone like Wayne.
I have been doing a lot of searching lately for these items. I should be able to post my homemade disc sander with variable speed drive next week.
the old sailor (aviation electronics technician first, US Navy, Retired)
 
I think if you are uncomfortable wiring the motor and VFD you should get help. You'll have to wire the plug to the VFD and then the VFD to the motor. But, frankly its not hard to do. At least with the KBAC 27D, don't know about the TECO; see Beaumont Metals web site for instructions. I don't know that you can get it prewired (that is, motor attached to VFD to plug). Another question, will you be plugging this into a normal household receptacle, or a 220? I was going to plug the KBAC 27 D into a normal household 110 (115) v outlet, and the KBAC 27 D will work for up to 1.5 HP (make sure to set the jumpers correctly, simple enough to do as long as you don't forget.) But, I was concerned because the motor will draw substantial amps and I thought the wire gauge for the household outlet was too narrow, so I had the line rewired with heavier gauge and converted to 220 v. I may have been overly concerned about this last point and those who are informed may say so.

Jay
 
Just a short comment here, with little to no electrical experience, and "IF" you do have the money to burn and you're full time professional knife maker, then I agree 100% to buy the 2 hp VFD setup from Wayne.

However, if money is of real concern and knive making is a hobby/part time affair, perhaps going "cheap" is a good way to grow into the grinder. My experience: I built a KMG clone a while back- looked at photos, liked the way it looked - easy to copy. I'm very hobby oriented knifemaker, so labor is cheap. I ordered some 1/2" X2" aluminum bars from ebay and built from that. My first motor was a 1hp 1750 rpm motor using 4-step pulley. Worked just fine when grinding with contact wheel. If with platen, the extra drag on platen reduces power so at higher belt speeds, the 1hp would just gag. At lower belt speeds 2,000 SFM there is plenty of power, but at 4,000 SFM just very light touch is all it would handle with a platen.

BUT, at my skill level, I could do a lot of work at 2,000 SFM and even 1200 SFM because the grind goes slower allowing me to learn.

I recentlly upgraded to a 2hp 3450 RPM motor with step pulley and WOW, crank it up to 4,000 SFM it sure will cut some metal!

To sum up, learning to use a 2X72" belt grinder - if you can pick up a cheap 1hp single phase motor, 1725/3450 rpm motor, go with that to learn on. With contact wheel you might be surprise just how well it works. With platen grinding, you'll outgrow it pretty quick, but remember, you don't have much money in a cheap 1hp motor picked up at garage sale/Craig's List type purchase.

As your grinding experience grows and you find the power lacking, then make the move to a nice 2hp+ 3 phase motor with VFD package from Wayne.

Scott, that link to a VFD/motor package is a good price. That is the same VFD I purchased for my lathe, I think I paid $130 for VFD and well over $100 for 1 hp motor. $200 for the package is a GREAT price. Nice thing about the motor in package, it's got both base and end mounts.

Good luck, and I'm sure enjoying my 2X72" grinder - KMG has got a good price on their basic grinder. Building your own has more costs you might not consider than expected - UNLESS, you can build many of parts yourself. I've turned all the idler wheels & drive wheels, etc on the lathe from aluminum bar I found. The 2" long board skate board wheels will work also - surprising how long they will last before wearing out. That is for the part time/hobby knife maker like myself who is not using the grinder every day.

Boy, this got longer than I planned. I hope it helps some.

Ken H>
 
Thanks, guys. I'm reading and digesting all the responses.

I'll never be more than a hobbyist. I'll be using 110v, which rules out the 2hp.
 
With a 20 amp breaker and #12 cord that is not too long, 2 hp can be ran on 120vac just fine. The motor will never know the difference between 120 and 240 - as long as the voltage doesn't drop over 3% under load - even 5% isn't really a factor. The problem with 120vac on 2hp motors is someone tries to run them on a cheap extension cord that might be 16AWG which would give LOTS of voltage drop.

As a hobbyist, a pair of 3 step pulleys with a cheap 1hp 120vac motor would give you a range of speeds and get some grinding experience. These can easy handle 4,000 SFM, but except for rough grinding, I'm more comfortable with 1200 SFM. 1 hp motor won't pull much more than 2,000 SFM before choking - that's with a Platen. A contact wheel will provide more power due to much less friction.

73 de Ken H>
 
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A GIB is a direct drive frame kit. Maybe someone has modified a GIB to use pulleys. Otherwise I've read good things about a Coote grinder. It's a two wheel grinder but works well with a three pulley setup for three speeds using a single phase, plug in the wall, motor. I'm using a 1 1/2 hp with the GIB and a VFD. I can stall it, but attribute that to poor technique on my part. I often profile on a platen and hollow grind 1/4" stock and don't feel under powered.

Jay
 
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Sticks said:
A GIB is a direct drive frame kit. Maybe someone has modified a GIB to use pulleys. Otherwise I've read good things about a Coote grinder. It's a two wheel grinder but works well with a three pulley setup for three speeds using a single phase, plug in the wall, motor. I'm using a 1 1/2 hp with the GIB and a VFD. I can stall it, but attribute that to poor technique on my part. I often profile on a platen and hollow grind 1/4" stock and don't feel under powered.

Jay
Click to expand...

I started with a Coote Grinder 2 x 72 with the 8' contact over 15 years ago and still have it. I have two 3/step pulleys and a 1 1/2hp 1800RPM motor.
http://cootebeltgrinder.com/
this combo will handle any of the flat Grinding I do, I have made a few hollow grinds,
I just prefer flat's and use the 8" contact for profile work & contours.

Laurence

www.rhinoknives.com
 
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