2x72 motor advice

Kevin McGovern

Kevin McGovern

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Jul 31, 2015
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I am looking to move up to a better grinder than my HF 1 x 30, but I'm still (and will remain so for the forseeable future) a hobbiest knifemaker. I am looking at building a Polar Bear Forge sling grinder and can do it all in for about $400. I have looked through the past threads on this, but this is more of a personal opinion question. If you had a choice between 1.5 HP direct drive single speed (I'm thinking 1800 rpm with a 5" drive wheel for a sfpm of 2355) and 1 hp with a VFD what would you choose and why?
 
A 3 HP with pulley system. There is no substitute for horse power.

Enjoy, Fred
 
if i was to choose between the two, i would go 1.5 with 3 step pulleys for different speeds.
 
Thanks. I would love 3 HP and variable speed, but my choices are limited to what is in my original post. The sling grinder is direct drive only. Once i move to my permanent shop, I will have more options.
 
That's a tough choice as neither option is optimal. Ideally you would want a minimum of 1.5 HP and variable speed is very nice and gives you more control when using a small wheel attachment or when shaping handles or running higher grit belts. I think if I had to choose, I'd go with a 1.5 hp single speed as the sling is a single set up machine and I assume you will be running a flat platen. I would use it for profiling and grinding my initial bevels and do handle shaping and higher grit sanding by hand.

A third option would be to save a little bit more and go with a 1.5 HP with VFD, it's not that much more if you use the TECO VFD. What your budget for 1HP with VFD option?
 
If you look around hard enough on eBay you can score a nice 3 phase tefc grinder and a Nema 4 vfd for a good price. I built my whole grinder for a little less than 300. Direct drive variable speed with a smvector Nema 4 vfd
 
It's not so much budget, although that is a concern. My shop, which is the 100 year old well house separate from my 100 year old house does not have 220. I may, or may not be moving into the detached 4 car garage that does have 220, but that is at least a year out. I have a bench mounted belt sander, spindle sander and disk sander so this grinder would be primarily for profiling and grinding bevels. That's my thought process anyway. So it seems like the consensus is the 1.5 hp fixed?
 
kdogmcg said:
It's not so much budget, although that is a concern. My shop, which is the 100 year old well house separate from my 100 year old house does not have 220. I may, or may not be moving into the detached 4 car garage that does have 220, but that is at least a year out. I have a bench mounted belt sander, spindle sander and disk sander so this grinder would be primarily for profiling and grinding bevels. That's my thought process anyway. So it seems like the consensus is the 1.5 hp fixed?
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I run my 1.5HP 3phase motor off of 110V 25amp circuit with no problem. I could switch to running off of 220V at any time.
 
If budget isn't an issue why not get a 1.5 with a vfd? That will run off of 110v just fine... The motor itself is about $120 (tefc, 3 phase so it works great with the vfd).
 
I haven't been able to find a 110v 1.5 vfd. I am admittedly ignorant of the technology. Where can i find that?
 
I just sent you a link to the motor, it's $114 w/ free shipping.

As far as a vfd, most of us use the KBAC 27d which will handle up to 2hp. This one is nice because it comes w/ the Nema 4 enclosure which you will need to keep any abrasive dust/moisture out. You can go cheaper w/ something else like a potentiometer (there are other posts here on this) if you wish. If you want to read through the entire manual and set it up yourself I believe you can find one for around $350. If you want everything set up for you and plug and play, then check out Wilmont Grinder's KBAC-27d, Chris Williams (owner) is extremely helpful and will answer any questions you may have about tweaking it if you get it from him. I have not needed to change mine since I got it from him.

If you go w/ the motor and a pulley system the pillow blocks and pulleys etc. will cost somewhere around $200 I have read recently, which you COULD just put into a vfd instead. As most will tell you here, a vfd is priceless for knife making. I don't make knives, but I do a lot of grinds on hardened steel and some handle work and I personally would choose less hp w/ the vfd control than vise versa, but that's just me. I actually have my 2hp motor scaled back to 3/4hp on my Wilmont TAG-101 right now, because I use my vfd to control multiple motors and I don't feel like changing the jumper each time I go back and forth. So I have it set for my weakest motor =)

Hope this helps!
 
Many others have bought the Chinese vfd off of eBay for about 130 and out filters on the vents. But since budget isn't an issue a kbac27d can run 110v for 1.5hp
 
Belt speed is critical if you want to do some serious grinding. We run 5400 sfm with ceramic belts. Time is valuable and sitting in front of a grinder is not my idea of fun so the faster it happens the better.
 
Fred, I agree with using bigger motors on grinders. I started with a 1 1/2 HP motor on my first grinder and was disappointed with the performance. I now run two 2 Hp motors and wish that I had bought 3 Hp motors. 2 Hp it fine for most jobs and I run 4500 SFM with them. Larry
 
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kdogmcg,
What is the amperage of the power circuit to the pump house?
What else is running on that power? ( lights, heater, pump?)
How far is the pump house from the main house?
Does the breaker panel in the main house have room for a new 220VAC circuit?

You may be better off to run a 220VAC 30-50 amp line to the pump house.

Another solution would be a portable generator. Most have 220VAC output ant more than enough current to run a 2HP motor. Just run it when the grinder needs power. It has the added value of providing back-up power when storms come.
 
Mr. Apelt, you are a gentleman and a scholar! I had never thought of using my 2 year old generator (that has never been used except for maintenance since I bought it after a week long outage). That will keep me in good shape until I can move into the new shop when the in-laws get out of there. And that shop has 220.

"Private Gump, you are a G@d d@$n genius!"

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I actually think for simplicity's sake, I am going 1.5 fixed HP 1800 rpm for now with the option to upgrade to a vfd when 220 power is reliably available. I will be making a good disk sander eventually and can use the 1.5 on that.
 
Remember, if you go fixed RPM now, that most likely is a 1ph motor. Then when you do wish to go to VFD, you'll have to buy a new motor to get 3 ph for the VFD to work. "IF" you're having to buy a new motor now at new motor price, just buy a 3ph motor along with a cheap Chinese VFD for ~$110 or so shipped. Put a filter over the air inlets on VFD and run it until it burns out due to metal shavings getting inside, which maybe well be several yrs later. Then buy a good NEMA 4 VFD and your motor is still good.

Ken H.
 
Jumping in here. I'm wanting to build a grinder and start making knives. I only have 110v to the garage. If I understand things correctly, I can get a vfd for $110 and a 3 phase motor for not much more to run off it? Can someone suggest a vfd on ebay and which motor and where?
 
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