Bearings

JG Custom Metal Works

JG Custom Metal Works

Joined
Nov 27, 2013
Messages
1,626
I just saw this video comparing Chinese bushings to high quality German bearings and it made me balk:

[video]http://www.liveleak.com/view?i=fc2_1411985084[/video]

It has since convinced me that I need to change all the bearings in my KMG. I have tested it's bearings and they perform in the same manner as the Chinese one in the video.

Has anyone done this before? If so, where did you get your bearings? Do you just press them out?

Anyway i suspect that this issues has been covered her before but I just thought it was an interesting video and wanted to share.
 
JG, The Chinese bearings on my KMG are sealed and have been spinning at 3450 RPM for five years (almost daily) with no failures. I believe that there are belter bearings to be had but the question is how good do they have to be. They are not made for expensive racing bicycles or soap box derby cars where it might make a tiny difference. If it makes you crazy then buy some others and figure out to replace them but I would not look for trouble where none exists. Just my opinion. Larry
 
I did have a failure with one of the chinese bearings that came in my KMG. It started making a screaming sound. I decided to replace them all.

No more problems with the bearings.

I found mine at the local Hardware store and an Auto parts place. Yes we tapped them out and the new sealed ones back in.
Larry is probably correct that if they aren't giving you any trouble why bother? Just listen and touch them from time to time to check for possible heat.
 
What makes you think the video was accurate? Do you know the person who made the video?

The difference shown in the video could be something as simple as lubricated vs non-lubricated. Long spin times do not equal long bearing life.

Chuck
 
Alpha Knife Supply said:
What makes you think the video was accurate? Do you know the person who made the video?

The difference shown in the video could be something as simple as lubricated vs non-lubricated. Long spin times do not equal long bearing life.

Chuck
Click to expand...
This is the thing that I have a hard time with. I believe that Chinese bearings are probably not of the same quality, but how are we to know who to trust. Anybody can make a video or do a review now days. Some people have an agenda, so who are we to trust?
 
You guys are probably right and I don't see Rob skimping on a few bucks if it was to make a big difference with his grinder. That being said I wonder if it would help the small wheel attachment run at higher speeds. I have some wobble with the small wheel attachment and was thinking it might help.

Anyway, thanks again gents, I appreciate your input.
 
I have well over 2000 hours on my KMG and it is going strong! that's a conservative estimate too

The only bearing I have ever had a problem with on knifemaking equipment was one on a generic small wheel... probably my fault as it was on my horizontal grinder... tracking must be even on them especially with the smaller wheels.

That being said I have German bearings on a 25 year old skateboard of mine, they are far superior than any I have used since and are going strong.
 
"Chinese Bearing" is not very specific. Is that to imply the entire country of China can not make a quality bearing? We trust them to make our cell phones, computers and TV's.

Quality is something you purchase in manufacturing... If you pay for quality then you get the quality even in China.

I buy my bearings from Graingers or McMaster Carr. The gives me a level of inspection from their company so I am not just buying blind and unknown product.
 
JG Custom Metal Works said:
You guys are probably right and I don't see Rob skimping on a few bucks if it was to make a big difference with his grinder. That being said I wonder if it would help the small wheel attachment run at higher speeds. I have some wobble with the small wheel attachment and was thinking it might help.

Anyway, thanks again gents, I appreciate your input.
Click to expand...

You shouldn't run small wheels at higher speeds


A 1/2 wheel is running 16x times faster than an 8" wheel



You need to go slow and you need to remove heat from that bearing.

Maybe in that case the ceramic bearings might be useful, but at what cost ?

If they fail and you need to change them, it's fast and simple - you're not in space and going to die if it fails
they are a minimum of 10x times the cost, with practically zero cost of failure or replacement


Remember that improper installation is probably a bigger factor than country of origin.
There's good chinese and bad chinese.
 
Last edited:
12345678910 said:
You shouldn't run small wheels at higher speeds


A 1/2 wheel is running 16x times faster than an 8" wheel

So that's 57,000 rpm at full speed

You need to go slow and you need to remove heat from that bearing.

Maybe in that case the ceramic bearings might be useful, but at what cost ?

If they fail and you need to change them, it's fast and simple - you're not in space and going to die if it fails
they are a minimum of 10x times the cost, with practically zero cost of failure or replacement


Remember that improper installation is probably a bigger factor than country of origin.
There's good chinese and bad chinese.
Click to expand...

^ Good stuff...

Small wheel - slowest pulley speed or even slower of you have a VFD... my belt just crawls by. With a small wheel you want the belt centered perfectly, lower tension than normal and run as slow as can be.
 
A dry, loose, shitty uncaged unsealed bearing can spin free for a long time without any load on it. That's not a measure of the quality of a bearing.

The ABEC 7 super precision bearings in the spindles in a machine tool cost from $1,000 to $3,000 per individual bearing (there are several bearings per spindle). You could literally buy an entire KMG for the cost of a typical bearing. And given the preload and lubricant they won't spin free more than a few moments. They're also handled in a clean room, not by some schlup with a metal rod...

What is a "weapon's grade" bearing? Is that something you launch from a sling shot?

The crappy Chicom bearings in my KMG are quiet and don't have any problems with vibration, runout or longevity and I've run them pretty hard and wet.

There is a cam follower bearing on the tensioner on the timing belt in your car. It was probably made in China. I'd be more concerned about that...
 
Trust me . . . I am Mr. Overkill . . . one of the things I was going to do ASAP was change the bearings in my Beaumont KMG.

I have friends in the PertroChem industry that are in design, maintainence, purchasing, etc . . . you name it . . .

I learned the bearing sets sold with a KMG are very overkill in spec and are approved for use by EXXON & SHELL . . . . this I do know for a fact.

That bearing is sold by FASTENAL & does appear on a long approval list for dozens of industrial facilities.

I was told by my millwright neighbor, unless you want to spend $100.00 to $125.00 per bearing you are not going to beat what you got.

Remember, it doesn't matter whose bearings you buy, there is NO WARRANTY.

$10.00 bearing fails, you eat it . . . . $150.00 bearing fails, you eat it . . .

If the bearing failure could damage or cause the destruction of the equipment it might make sense to better your odds. . . .

But that is all you are doing . . .

If you are really worried about it, buy an extra set from Rob & keep them on hand.

My 2 cents . . .
Steve
 
You must log in or register to reply here.
Back
Top