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Converting my KMG to direct drive and other mods


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My KMG has been a source of angst for me since I got it. The pulley system is noisy, causes a shitload of vibration, and tons of power loss. My skinny ass could stall it, and that just shouldn't happen. It tracked poorly, and I spent WAY too much time dialing things in, checking for runout, lining things up... Some things made differences, but it was never right. So, I called in a friend and we looked into what it would take to make it direct drive. The idea was to make this an EASY conversion, should anyone else want to do this. It assumes you have a 56C face mount motor. Mine is 1725RPM, 2hp, with a KBAC-27 vfd which I run in 2x mode (speed doubled). The adapter plate and motor bracket use the existing pillow block mount holes to bolt to the KMG body.


My machinist friend Joe made this prototype.

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Other than being easy to do, it also means you aren't permanently modifying the grinder, so should you choose to return it to stock, it's simple.


One of the issues had to do with the length of the factory pulley shaft - it's quite a bit longer than a 56C face motor's output shaft. We could have just had the drive wheel sticking off the shaft a bit, but that's icky. Joe elected to make a custom drive wheel. This one is 5.5" in diameter, with an offset to compensate for the difference in shaft length:


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With everything mounted and ready to roll, you end up with this:


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As you can tell, I've also added an additional tool slot. That sucks up a lot of real estate, so along with moving the drive pulley back AND increasing the drive wheel diameter, you can quickly run out of belt length. My 12" wheel just barely fits. Nonetheless, every one of my attachments works, including my Bader double billy roll, which eats up belt length like there's no tomorrow. The flat platen and contact wheels are a custom rig I made, with a 2" wheel on top and a 3" on bottom. That's one thing my old Wilton got right. Should be a pinch smaller up top (1-1/2" would be dandy), but I had the wheel, so there it is.


While I'm at it, here's a couple shots of the gas strut tensioner and the monster custom ape-hanger tensioning arm:


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Here's a quick vid of the grinder running wide open with the 12" wheel - previous to this modification, that belt would shift as much as 1/8", and it could NEVER have been run at this speed. The vibration was unbearable. Even the noise is reduced dramatically!


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You could have just mounted the motor to the base and not have had to fabricate the bracket. You then just have to make sure that you have mounted the motor square to the frame. You will be amazed how much quieter it is with less vibration and more power.

 

Let me know if I can help you,

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Hi Wayne,

This bracket is intended for those of us with motors that DON'T have mounting brackets. The only mounting option I've got to mount my motor is C face. Otherwise, I certainly would have just done it the way you're describing. I'm not certain I understand where you feel this mounting system would have any more vibration than using a motor with a foot mount, but I assure you it doesn't.

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Matt, This set up is a great idea. I don't have any issues with my KMG that I can think of, but this might create a little extra room on the bench, and we all need that! Besides, if I can improve the machine's efficiency, I'm all for it.

 

BTW, I have had problems with those gas struts failing over time. Any problems there?

Edited by Joshua States
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If my KMG ever gives me trouble that looks like a brilliant solution! Quite possibly the way to go once a VFD enters the picture as well. I can see how the gas strut would dampen vibration better than the spring.

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looks great. i made many of these same mods to my KMG recently, but have moved shop since, and have not been able to put it to work since changing things up. i like the wheel having that offset. i had a real problem with the first wheel that i tried. there was not enough stem on the motor! luckily the 6" wheel that beaumont sells has an offset threaded channel, so the screw gets more purchase on the stem.seeing your mods really makes me want to get out to the shop and get on with things.

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I'm designing a new stand for my KMG because I want the ability to flip it horozontally, and I plan on doing a direct attach motor conversion as well (in fact I plan to buy the parts from the same fellow Matt had his made by. What I'm working on right now is a good way to hinge the base KMG off of the KMG baseplate that I already have, because I'd like to use the baseplate as my stand 'top' and keep my tooling tree and VFD mounted there I need to decide if I fabricate a lift-up pivot similar to a TW-90 so that it pivots such that the belt is 'up' or I could just simply build a hinge so that it tips out away from the stand to hang off the side with the belt 'down' which would take almost no fabrication but not be as nice to use.

 

I kind of like my grinder to be fairly high compared to what I've seen a lot of people position theirs too. Currently it's sitting on a 29 inch tall standard height dining room table and it's much much too low for me. I like my center of the wheel at around 44 inches height so i'm grinding at mid-torso height

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Haven't had it long enough to have one fail, Joshua, but considering how well it works and how cheap they are, I'll gladly replace it before I go back to the spring.

What size gas shock did you buy and where did you get it?

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One word of note - this kit only bolts to the upright holes where the pulleys were mounted. If you're planning on making your grinder vertical/horizontal, you will likely need to drill and tap another couple holes in this as well as the baseplate for your grinder. I have no intention of doing that mod, so we didn't engineer it into the equation. Shouldn't be a big deal for you to do it, though...

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What size gas shock did you buy and where did you get it?

 

Josh, most of my mod ideas stemmed from a thread on Bladeforums which David Sharp began on his mods. Not sure if cross-forum posting is allowed, but here's how I guess I'll find out!

 

http://www.bladeforums.com/forums/showthread.php/949335-How-to-make-a-KMG-better-(GIB-content-also)

 

He used a 20 pound strut, I think. Mine is 40. I may, in the future, try a stiffer one, but so far this works great!

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Out of curiosity, has anybody here used a Lovejoy coupler to do this?

 

Yes I went to direct drive with a larger drive wheel and a coupler it works great but takes some tweaking to get it aligned and of course you need the room off to the side I'll take some pictures to post.

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  • 1 month later...

you know you've been grinding for a while... when you've leaned into the belt enough times stalling or slowing down the grinding belt that the drive belt has slipped enough you start smelling rubber burning. Thankfully it was just the pulley that was over heating, not bearings or anything. This is why I'm both converting to direct drive, and going from a 2hp motor to a 3hp motor.

 

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...wonder if you'll think you needed to upgrade to 3hp after you convert to direct drive.

 

Of course, if you can, why not, right? More power never hurts, and I'd bet there's greater torque available at lower rpm, and that's usually where I would need it, anyway.

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Frogfish: Where did you get that table arm setup? That is sweet!

Joshua, I just saw that Frogfish hadn't replied. Pretty sure what he's got there is a MAP arm from Michael Kanter. Don't think they're available anymore, but just in case I'm wrong, here's his website:

 

 

http://www.adammichaelknives.com/purchase.php

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  • 2 weeks later...

I finished installing the 56c direct drive conversion for my KMG grinder, upgrading to a 3hp motor and VFD at the same time. My 2hp motor and other VFD will be used to build a disc grinder. The next thing to build is a pivoting base for between the KMG and the base-plate, so that I can use the KMG horizontal or vertical. I've also got set up a mist cooling system to use with the grinder too, so I can grind heat treated blades without risking the loss of temper.

I better not be able to stall this out anymore, 50% more hp and got rid of the belts and pulleys!

 

https://youtu.be/Z9IvRfob_1M

 

Edited by Justin Mercier
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