How long do belt grinders last

Alden Cole

Alden Cole

Well-Known Member
So I am looking at buying a used 2x72 kmg grinder, and the guy says that he has made 500 knives on it. My question is whether the wheels or motor or anything would be bad by now. It looks to be in very good condition by the pictures, but I just want to be sure. Thank you!
 
As with any machine..... it depends on how well it was cared for. I have a KMG in the shop that's been here 20+ years..... and it's ground over 2,000 blades easily. I've had to replace a couple of bearings, but beyond that simply blowing it out with air, and ensuring any bearings that are not sealed, are serviced/lubed has been all I've done. If the motor is single phase, it's likely not even broken in yet, and if it's 3 phase with a VFD..... it'll likely outlive you. :)
 
I have a Wilton Square wheel that I bought in 1992 that is still going strong. I also have one that was supposed to have been made in the 70"s in California that is set up with a 4 groove pulley on drive and motor that gets used all the time. The only thing I did was take the 9 1/8 inch grind wheel and replace it with a 10 inch.
 
There is just about nothing on a KMG that can wear out other than bearings and the motor. Platens and wheels are wear items, so you can't count those. Put glass on the platen and it will last years. Grinders really don't work that hard as machines go. I wouldn't think twice about buying a 20 year old KMG. Mine is 6 years old and other than the dirt it's in exactly the shape it was in when I got it. I have not changed any bearings yet. I am on my second platen. The first one lasted 6 months. Then I learned about putting glass on it, which I did for the second one and it's still going. My glass has been on there so long it's not even flat anymore, so it's time to change that- whenever I get around to it. My blades are still coming out fine so I'm in no rush.
 
Sorry for the delayed response, I had to decide pretty quickly, and couldn't really wait for an answer as I was sure someone else would snatch it up if I didn't hurry. I got a very good deal on it, I think the only things that will need replaced anytime soon are the platen and the drive belt. I will also have to get 220 wired for it. All the info is very encouraging, thank you for taking the time to respond. The guy who sold it to me also threw in around 100 belts, so I'm pretty pumped!
 
Ember Knives said:
Sorry for the delayed response, I had to decide pretty quickly, and couldn't really wait for an answer as I was sure someone else would snatch it up if I didn't hurry. I got a very good deal on it, I think the only things that will need replaced anytime soon are the platen and the drive belt. I will also have to get 220 wired for it. All the info is very encouraging, thank you for taking the time to respond. The guy who sold it to me also threw in around 100 belts, so I'm pretty pumped!
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You don't technically need 220 wired for it. A VFD like the KBAC 27 will take 110VAC in and make 220 3 phase for you. Of course you'll need a 3 phase motor, but an Ironhorse is very cheap. You will lose a little bit of horsepower by running single phase into the VFD but I don't think you will ever notice.
 
I should have specified that this is a three speed, 2hp motor. So I'm guessing that I will have to wire 220 still? Thanks.
 
Ember Knives said:
I should have specified that this is a three speed, 2hp motor. So I'm guessing that I will have to wire 220 still? Thanks.
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Im assuming when you say it is a 3 speed then you are talking about step pulley setup. While it isn’t as convenient as a VFD, certainly still fine to use (and can’t really fail on you). In this case, to use it as-is with the step pulleys then, yes you will need to wire 220 for it. Technically, you could buy a VFD and run 110 into it and convert it to 220 with that. You will lose some power and the step pulleys would become mostly meaningless at that point since you could just use the VFD for variable speed control.
 
Yes, It's a step pulley system, I think my dad will help me wire 220 for it. I will try to post a pic of it soon.
 
That is most likely a 1 ph motor you have since it's a step pulley setup. if it's not wired for 120 vac your Dad should be able to rewire to 120 VAC and run on a normal outlet. Most 120 VAC outlets are off a 15 amp breaker, and while a 2hp motor will typically pull 14 amps full load, the light load you'll be running except for HEAVY hogging will be pulling a good bit less amps. The only problem might be the starting current which can be pretty good. I doubt you'll have a problem starting, I've ran 2 hp on a 3 step grinder a while with no problems.

Where the 2 hp motors have problems on 120 vac is with compressors and the light, even with the unloader valve they tend to have a bit more current that a 2X72 grinder does - especially running a contact wheel. The platen will put a tad more load, depending on covering on the platen. I've used glass, but curently am using a graphite pad.

The proper answer is to spend the $300 for an Iron Horse (or other) 3 ph, 2 hp motor and a VFD drive for variable speed grinder, but that requires 220 vac in shop. The KBAC drive is the only one I know of that will run on 120 vac, and it's almost $300 or so.

As mentioned I used a 3 step pulley setup for a yr or so and didn't feel like a VFD really offered me anything - UNTIL I built a VFD grinder - boy what a difference!
 
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What it comes down to is this: How hard / expensive it will be to run 220 to your grinder, versus buying a VFD and a 3 phase motor if you already have a regular 110 outlet handy. As Ken said, you can get the VFD and motor for about $300.

When I first started making knives, I didn't have 220 in the garage but my garage was right next to my laundry room. I put a dryer plug on the end of a long cord and I would plug my grinder into the outlet for the clothes dryer to get my 220. Of course this meant I couldn't dry clothes while I was making knives, LOL. But it was an easy workaround and it worked fine for about two years until I moved.

Another possibility: take a good look at the nameplate on the motor. It may very well be a dual voltage motor that can be wired 220 or 110. This may be as simple as changing the connections inside the motor's connection box. And if not, a quick run down to Harbor Freight for a 110 volt well pump motor will do the trick. If you can't read any numbers on the motor (frame size) then measure the diameter of the motor shaft to make sure that the motor you get has the same size shaft so that your pulleys will fit.
 
So what kind of vfd would you recommend? I will check the motor for the dual wiring thing. I may end up just taking the advice of just buying a vfd and new motor rather than wiring 220.
 
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As mentioned above if you only have 120vac then the KBAC is about your only choice. If you can get 220 vac the you can use either the $300 plus KBAC or use one of the Chinese VFD drives for $60 to $ 70 shipped from USA. They are all open frame (NEMA 1) enclosure so require a filter over the air inlets. Here is a VFD I've used with success - easy to setup with only a few parameters. https://www.ebay.com/itm/122794378916? For $60 shipped out of Kentucky. I'm running 3 of them.
 
I see you have got you a nice grinder, as far as how long a grinder lasts I bought a new Burr King 1 1/2 HP. vary speed 24 years ago and all I have done to it is replace the bearings in a 1/2" small wheel, and have made a lot of knives and used it for what else I could. Just wire in 220 you will need it for your disc sander and heat treater. Deane
 
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