Is variable speed REALLY that great?

A

AlphaMoose

Joined
Sep 1, 2016
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So I'm about to purchase a KMG grinder, and I was pretty set on/happy with the model with the pulley system for adjusting speed. Seems like everyone is gaga over variable speed though. Seeing as that adds a BIG ol chunk of money to the cost (like 700 bucks if I'm not mistaken), what is the big push? Is it really gonna make that much of a difference, and most importantly am I gonna regret it if I don't get it.
EDIT: Also would it be possible to get the regular non-variable setup and purchase a VFD later? I really want to get started and if I NEED the variable it's gonna eat my anvil budget.
 
Back in prehistoric days, we didn't have variable speed grinders. We managed to turn out some very fine cutlery.
I only recent bought a VS grinder-and I bought it for a very specific purpose in my knife restoration business.
You don't NEED VS, it just makes things easier.
 
Gotcha. I mean I figured as much. The standard model still has 3 speeds. This is still gonna be a GIANT step up from the Grizzly 1/4HP 12x4 belt sander I had when I was 15. Think I'm just gonna standard and get more belts.
 
I started with a 3 speed grinder and felt like King of the hill but then I built a new grinder and went all out. Let's just say I could go back to a 3 speed but I would not be happy. VS is really nice for the finicky belts that like x speed. I find that when roughing I run as fast as she will go 4500sfpm. But when using finishing belts like the gators I find I like to adjust them till I feal them cut. But if money is tight then go 3 speed and then upgrade in the future and use the old motor for a disk grinder. I don't mind single speed disk grinders becaus I only use it for flattening handle scales.
 
variable speed is more like 300 to 500 depending on source and size. if dollars are tight, get two drive wheels so now you have 6 speeds.
 
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.
 
Yes you can live without VS but once you try it you will wonder how you managed before it. I started with 3 speed pulleys and it worked well for a few years. the thing about the pulleys I found I just left it turning as slow as it would turn and did everything with that speed. Why? because it was more of a hassle than a help to move the belt around on the pulleys. I think being able to slow the grinder way down really helps when matching up your plunge lines without chasing them back onto the ricasso. also the higher the grit belt the slower I like to run the grinder. I shopped around when I stepped up to VS and found the controller here

https://motorsandcontrol.com/products/9520-kbac-27d-gray-inverter?gclid=CIzn3ZD3jMUCFWRp7AodsWIAaw

and bought the motor on fleabay for like $130 shipped. Wayne Coe will sell you the wiring harness with cable glands.

Good luck with your decision!
 
I've been using my 3 speed KMG for a few years now and still haven't felt the "need" to upgrade to variable speed. I do not sharpen my knives with the grinder though, so having the capability to lower the speed to 100 SFPM or less, isn't a requirement for me. My view on disc grinders differs from JT. I went variable speed with my disc grinder and would not even consider using one without it.
 
Just get the variable speed.
If you just want to run it at only a couple of places on the dial, you can.
But you won't.
 
Never had it so I dont miss it. I am sure I would use the heck out of it if I had it. I chose to go three speed for now and then upgrade later when I ran into a situation that required it. That kind of money was just better invested elsewhere for me.
 
It's not just about ease of speed adjustment, it's a larger speed range. VS can give you access to a lower speed range than you can usually get otherwise. I find myself using that lower range a lot.
 
i have VS use it at 40 60 and 80 hz most the time if i had a belt i guess i coudl get pullies that woudl do the same thing but it would mean stopping to change speeds every time i wanted to do something different or if i wasa sswapping to my small wheels (jsut one more thing to be done thats not making knives/parts
 
I built my first 2x72 as a 2 speed. I built my disc grinder with a variable and I'm building my next 2x72 with a variable. Obviously you don't need it to make knives. But it's much nicer to have for a variety of reasons.

To me it's like the difference between buying a car with a tiny 4 cylinder and no creature comforts when you have the option, for only a bit more money, to get a V6 with only slightly lower fuel economy, power windows, locks and A/C. Either one will get me to work every day. One will do it a little cheaper. The other one is much nicer to get into every day for the next 8-10 years.

You can always add a VFD however, so the analogy isn't quite perfect. The problem with that being if you buy the equipment with a pulley system it likely has a single phase motor, and upgrading to a VFD in the future means buying another 3 phase motor.

I thought about constructing a variable belt clutch, like you'd see in a Bridgeport J-Head, in order to save money on a VFD. Then I realized 3 phase motors in the size/rpm/feature range were much easier to find for reasonable prices than single phase motors, and the time I would invest in building that clutch would easily surpass the few hundred dollars of buying a VFD.
 
Well, I used a 3 pulley setup for a couple of years and didn't think there was any "real" advantage to a variable speed setup..... until I got one. There is just no comparison!!! and drop that shaft 'n pulley arrangement and go to a direct drive!!! See if KMG will sell you the grinder for less price without the shaft and pulleys, buy your own motor and VFD. 2 hp 3ph motor is $130 to $160 depending on RPM, and a NEMA 1 VFD is $116 or so shipped. Put a couple of filters over air intake and do your grinding. When it does burn out a few years later you can spend the extra money for a NEMA 4X motor if you wish.
 
Used a 4 speed pulley for years. True 4-speed with a 4-step pulley and slide bar arrangement on the motor, not two three step pulleys that dosnt really give you as much..
When we got a VFD it was like seeing the mountains for the first time again.
 
I went a similar route to many posters here. I built a 3 speed, which was a super improvement over my Craftsman 2x42. I couldn't believe how good it was, and wondered why I put up with the Craftsman for so long. About a year later, I converted to a direct drive three phase motor with a VFD. Once again, I couldn't believe how good it was, and wondered why I didn't go that way in the first place. Do what you can, and it will improve your abilities until you can do some more. The simplest way I have put it is this: slower speeds help you screw things up slower. There's more margin for error, and the mistakes don't hurt as bad, when you're able to turn the grinder down to 10-20% for the critical maneuvers.
 
VFD shines at the low speeds IMO. I love to run it very low when finishing or grinding in an edge bevel. Another thing you might consider is if you will eventually do a direct drive conversion. I don't think a pulley system is going to be very conducive to that. I know why you're making this thread. You want someone to tell you that a pulley system is every bit as good as a VFD and you don't need to spend more money. Everyone wants more for less, but in this case, you really DO get what you pay for. Pulley systems just aren't able to access those really SLOW speeds. It's tough to have to plop down the extra dough when you're already shelling out a good amount for a large purchase. You'll be happy you did in the long run.

I've seen guys who can make some of the most beautiful knives in the world using files and sand paper. I imagine it took them an ungodly amount of time to do it though. Just because you can get by with doing something low-tech, doesn't mean it's the right course for everyone. The guys who make blades like that with files are an anomaly.

You could always hold hold for a little longer and try to find a deal. That's what I did. I set a date for when I was going to buy the KMG with the pulley setup and try to find a VFD KMG for less in the meantime. About two weeks before pulling the trigger on the pulley setup I found a fully kitted up KMG with VFD, small wheel attachment, extra tool arms, and a bunch of belts for the same price I was gonna shell out for a new pulley setup. I had to drive 20hrs to get it, but it was worth it. Keep your eyes peeled. Good luck.
 
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