Whats wrong with my KMG 2x72??

T

Timy

Well-Known Member
Alright guys, I have had sneaking suspicion ever since I got my kmg that something wasnt quite right. It grinds well, and I love the machine to death. I will take it to my grave. Its the 3 speed pulley, with a leeson single phase motor. Having said that, I NEVER use the fastest speed because frankly it scares the sh*t out of me. Its so loud when I do use it on its fastest I need ear plugs, on med and slow, no problem. It sounds like its only a step away from blowing up. Again just my opinion, I dont have a lot of experience around these types of machines.

A good friend of mine just finished setting his up, I helped him build the stand, so same base plate, same motor, same grinder, same belt, same tension, same stand. Think we have eliminated all variables here, and his sounds fine when on its fastest, mine has this harmonic wine that like I said sounds like something is wrong.

So we recorded them both, both in a close shop, with the same phone, from roughly the same distance.


Any of you very grinder minded great folks, if you could give each video a listen and tell me what you think I would be INCREDIBLY grateful!

ok first one is his



second one is mine



Lemme say, I have made sure everything is tight, nothing is dangling, or rattling, my only other guess is the bearings holding the drive shaft, or the bearings in the small wheels above and below the flat platen.

Again thanks for taking the time to look at this.
 
Look on the side of the bearings and you will see the word "china" I had to replace the ones in the idler arm right after I purchased mine.
 
I have an older KMG grinder. There are two grease zerks on the pillar bearings that need to be greased on a regular basis. Does your machine have these?
 
Couple of questions and suggestions:

What kind of belt are you using between your motor and drive sheaves? If you're using just a standard V-belt, I would swap this out with a Fenner Link belt.

Is the machine still fairly noisy when you run it without a grinding belt. Try running JUST the motor without a drive belt. This should be VERY quiet. Now put your drive belt on and run without a grinding/sanding belt, so that only the motor and drive shaft assembly is turning. Does it sound almost an noisy as when you're running a grinding belt? Chances are it's your drive shaft bearings then. Do they feel hot after they've been running a while?
Have you ever greased them?

You might try swapping them out for a new, quality bearing and make sure to pump a little bit of grease into them (but NOT TOO MUCH).

Where there's lots of noise, there's usually vibration and eventually heat. Do you feel a lot of vibration on the bearing housings?

Is your drive shaft still running true? Are your bearing collar set screws still tight? If you pull laterally on the drive wheel, is their play in the bearings or the shaft?

Now, if it's still fairly quiet without a grinding belt, then the vibration is probably coming from your tracking wheel or idlers.

Let us know what you discover.
 
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Awesome guys thanks for the responses. Well I noticed after tearing it down to paint, one of the drive shaft bearings is a little looser than the other, but after running it without an abrasive belt its loud but not that awful whine you feel in your bones so to speak ha. Still I think replacement shafts would be a good idea.

Regarding the little mini ports for grease, I swear I read more than once those are for a different style of bearings just happened to be on these? something about the bearings themselves are sealed for life, but the housings where designed for older bearings? My KMG is about a year old now, maybe year and a half.

Ill try the without a drive belt then with, still without abrasive belt. I dont have a v belt anymore, just updated to a link belt in hopes it would quiet things up a bit, only difference I saw is a little smoother.

Also quadruple checked everything is tight after reassembly when I painted her, but honestly noise was the same before and after assembly.

So pulled on drive wheel and pulley, little and i mean tiny bit of play on pulley side, drive wheel feels like Im trying to move a tank. With and without drive belt noise is similar, little more vibration noise with drive wheel attached.

So the grand daddy, put an abrasive belt on just the TOP wheel of the flat platen, no platen installed and cranked her on. Then tried it on just the BOTTOM wheel.

Guess what..... Its the Bottom wheel making all the noise Im referring to.

Seriously, YOU GUYS ARE FANTASTIC!!!

Andrew, Jim, Laurence. Thank you fine gents for taking the time out of your saturday to help a newb! It is so incredibly appreciated. Thank you guys.

"does a little dance"

Tim
 
Bummer man! Sorry to hear.

I ground my last blanks at full speed and it worked fine. All the speeds are loud to me, so I wear ear plugs regardless.
 
Jim Moenck said:
I have an older KMG grinder. There are two grease zerks on the pillar bearings that need to be greased on a regular basis. Does your machine have these?
Click to expand...

No need to add grease to those Zerk fittings

The bearings in those fittings are sealed. The Zerks don't go anywhere.
Rob Frink has verified this in a forum sometime, he buys the pillow blocks and just doesn't bother to take the fittings out or put plugs into the holes.





If you put them together, the side pressure on those bearings by tightening those screws can vary.

Next time you try to track that sort of thing down, you can use a mechanics stethoscope.

Put the round end of a broom handle in your ear pressing up against your head, put the other end of the stick at different points / bearings

The loudest point is the problem
 
hopefully you can get in touch with the folks that sold you the unit and have them replace the loose and squeaky parts.
i have found on my machine that it is easier to use a slower speeds and that belt life of finer grit, >120, is a lot better. remember, your belt grinder is a finesse machine, a light gentle touch is required.
 
Smaller wheels should probably not be spun at high speed. Seems I remember being told low speed only on the 2" and smaller.
 
1725rpm leeson 2hp single phase motor


Steve, that's only on the small wheels for the small wheel attachment.

The little wheels on the platen, have bearings rated to 10-12,000 rpms
 
I'm going to take a different tack and say speed and pressure is everything if your running ceramic belts, especially the course grits, 36, 40, 60, 80.
Top end on my 3 hp KMG is 5400 sfm and it removes metal in a hurry. One benefit to using speed and pressure is it takes fewer passes which means fewer opportunities to make mistakes. It also means the belts last longer. Ceramics are meant to be fractured after they dull; this will give a new abrasive surface to work with. Using slow speeds without pressure will "load" the belts which is very hard to correct.
The Zerks fittings on the early KMG's are not operable the bearings are sealed.

Fred
 
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