Is variable speed REALLY that great?

You can always upgrade later. I started with 3 speed on my kmg. Just sell the single phase motor later when you upgrade. If you get a disc later, you can run both motors with your vfd. You can do it cheaper than $700 too if you do it yourself.
 
As you use finer grits on your belts to finish a blade you should lower the speed of your wheel or platen to avoid heat build up and even burning through a thin blade. You can adjust your speed quickly as you change belts with a VFD. My opinion is get it now and have one less thing to fiddle with when you are concentrating on making a nice knife. I would never go back to using step pulleys. Larry

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Some may consider variable speed a luxury and I partly agree but for certain tasks it is darn near a necessity. For myself I consider the time I invest into each knife valuable and if I can reduce my time while still producing a good product then I will go that route. For me there is nothing more frustrating than being held back by my equipment. Can you work around obstacles? Of course. But why would you want to. I understand the increase in price is significant and to that I would say ditch the KMG and go with a pheer or esteem. You can grab a 454 Pheer for $200 more than the KMG. For that You get variable speed, direct drive, and a secondary tool arm slot. Those to me are EASILY worth the extra $200. If you are stuck on the KMG then that is a different story and having to justify a difference of $700 is a far greater investment than $200. Ultimately, you will no doubt be happy with either. But I can almost guarantee you, if you go variable speed you will never go back to pulleys. ;)

Blessings,
Joshua
 
You will at some point regret not getting one. You will never regret getting one. They are worth the money.

Hoss
 
Your question is like asking if indoor plumbing is great? You can certainly get your business done without it, but ... it's a whole lot nicer not having to make the trek to the outhouse in the snow. :)
 
I don't have the strength in my hands and arms that most do.I found that by being able to control the speed - 2X72s and disc - I was able to better control my grinding.
Frank
 
For me, the cpvariable speed has eliminated most of the hand sanding. I was on a craftsman 2x42, spconverted to 72". There were always nicks and scratches that took a long time to sand out by hand. Slowing the belts down minimizes this, and burned edges are a thing of the past. It really is that much better.

It's much like a welder. A cheap one will give you three or four settings, but the good ones are really variable, so you get the exact weld you need.

When I priced it out, a used three phase motor and Kbac-27d was the same cost as buying a new single speed motor and step pulleys. Of course, the single speed could be bought used too, saving some money, but if you shop around, you will get set up pretty cheaply. I just got a 1hp, 3 phase motor for a disc grinder for $78.00 shipped. I had the VFD already, as well as the 9" disc.
 
woodster said:
i have asked the same question, and have not heard an answer that explained how it's better. all i hear is "its the way to go!" i believe its all convenience and the knife being ground will not know the difference. i have also heard with the vfd the torque is the same at all speeds, but with the pulleys it changes. i can stall my kmg on the fastest speed, but it is difficult on the slower speed because there is more torque. hopefully someone can confirm this.
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IMHO, with VS you can get increased belt life, especially with belts finer than 100 grit. with VS, you can run wet and the water stays on the belt, not on your face shield. with VS, you may find you have more control when you grind. with VS, you are grinding slower, which is helpful with doing finishing or working with thin,<1/16", stock. VS works best with direct drive, so you don't have pulleys and belts to mess with and create guards for. VFDs are programmable so you can set whether you want constant torque or constant speed, how fast the belt accelerates, it keeps watch over the motor and will stop rather than allow over current condition.
you should be able to find a TECO FM50 for $150 delivered, if you shop eBay you can find a motor for $150 or less. buy the bare bones grinder package. if KMG is not available in direct drive, shop, there are many good grinder builders out there. if you get a VFD, buy some 4 conductor cable and some 3 phase twist-lock plugs. you can run several machines from the same VFD, one at a time. I currently have a 3 phase 2x72 and two 3 phase disc grinders. next is installing a 3 phase motor on drill press and 4x36 metallurgical grinder.
ANOTher thought, if you have 240vac in your shop, get a VFD rated for 2hp or 3hp. A 3hp VFD will safely drive a 1hp motor but you can't run a 2hp motor with a 1hp VFD.


scott
 
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DevinT said:
You will at some point regret not getting one. You will never regret getting one. They are worth the money.

Hoss
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Yup

I have a three speed KMG and kick myself in the rear on a daily basis for not getting variable speed--it will be my next upgrade without a doubt.
 
One thing that hasn't been talked about is the ability to run in reverse with a vfd. I know it's not a necessity but I find myself using it for more and more tasks.

Sent from my SM-G920V using Tapatalk
 
I built a NWGS with a step pulley, and debated for years about upgrading it to a VS set-up, but always figured the money could be used elsewhere for other much needed tools and upgrades.
THEN I built a much nicer grinder with all the bells and whistles, including a VFD, and I almost immediately regretted not getting a VS setup sooner.

Don't get me wrong: 3 speeds will get the job done. Heck, I could even get buy with 1 speed if I had no other choice, but once you start using a VFD and experiencing quick and easy speed changes, the versatility of lower speeds, and just the all around convenience, you'll wonder why you puttered around with step pulley for so long.

And truth be told, these days, VFD and a decent 3 phase motor can be found for not that much more than a step pulley and single phase set up.
 
Is variable speed REALLY that great? Yes

We have 4 2"x72" grinders. The first grinder had a single speed motor with step pulleys. Now all the grinders are variable speed.

The flexibility of working different materials at different speeds is worth the cost.

Chuck
 
*sigh* ok ok. I'll bite. Ya'll are killin me :rolleyes: Waiting one more paycheck won't kill me. And yes I am serious about this. I got all my "just messing around with steel" out in my mid teens.
 
I gotta say though. It really makes me mad how KMG just WONT sell a product you can use right away. I mean, the 3 speed is bad enough but at least you can get the package of everything you need to wire it. The VS just says "Obtain a 14/3 cord". Like, excuse me, this is a $2k tool. How about you SUPPLY that.
 
Did you ask them about selling the unit without the 3 speed pulley setup and only the base grinder so you could mount a 3ph motor to the grinder base and have a direct drive grinder?
 
josh81 said:
One thing that hasn't been talked about is the ability to run in reverse with a vfd. I know it's not a necessity but I find myself using it for more and more tasks.

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A very knowledgeable machinist warned me that belts have a preferred direction, so now I have to try to remember to reverse the belt when reversing the motor.
 
The Mighty Ginsu said:
A very knowledgeable machinist warned me that belts have a preferred direction, so now I have to try to remember to reverse the belt when reversing the motor.
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Huh? Most VFDs have a port that can utilize a reverse switch. You don't have to reverse the belt. I have never reversed the belt on mine and have used the reverse function a ton. It's real handy when sharpening.

I think you'll be happy with going with the VFD. It's worth it. If I had to do it over again I might consider another grinder over the KMG. I love my KMG but I'm really a fan of the direct drive. I get a lot of wobble with mine and the tracking isn't as great as I've seen with other machines. I can level it out by adjusting it but it's just kind of a PITA. I'd probably look at the Northernridge Tool 2x72 or possibly the Pheer. Of course the TW-90 but that is pretty dang pricey.
 
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