Author Topic: eBay accuracy humour  (Read 89 times)

Carpenter84

eBay accuracy humour
« on: July 11, 2019, 05:59:10 AM »
I noticed my live center smoking last night. Lol... i put new bearings in it and packed it with grease about a year ago... gonna assume I screwed up and she no good. Haha

Perusing eBay this morning looking at live centres. Check out the accuracy the Chinese advertise! They must have so little idea of what theyíre talking about that theyíre just making up numbers at this point. Check out the first photo... what is that number? Is that even a measurable amount??

I want a center with that long nose. I always have a problem getting my tooling in close to my center.

The second photo. 20 thou?!
The third photo is the only one thatís reasonable.
And the fourth photo is shars. Which i would buy, but on every item Iíve looked at from shars in the past all have ridiculous shipping.. really, just outlandish shipping for somewhere thatís not actually that far away.
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

woodchucker

Re: eBay accuracy humour
« Reply #1 on: July 11, 2019, 10:46:05 AM »
can't talk about the accuracy, but I will say, that I would be bothered by 3 bearings.
it's easy to align two things, it's hard to align three.  would it be better with 3... maybe, but in my mind, a thrust bearing in the back, and a bearing in the front should suffice. would 2 in the front work better...??? maybe, but aligning that thrust to the two in the front might cause more problems if not exactly located.


my 2 cents... That's why there are flex couplers for motors that allow multiple bearing surfaces to be slightly out of alignment.
would an integral set of bearings be better aligned.. probably, but there's still room for error.
Jeff
Clausing 8520   SB Model 9a - power hacksaw, Milwaukee band saw in a table.  Delta Rockwell Surface Grinder (not online yet .. being rebuilt where am I going to stick this)
For pics: https://imgur.com/user/woodchucker/posts

Carpenter84

Re: eBay accuracy humour
« Reply #2 on: July 11, 2019, 12:46:16 PM »
Ya I wondered about that too. I asssssume it's 2 front one thrust. Unless it's actually just three big balls rolling around....
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

4GSR

Re: eBay accuracy humour
« Reply #3 on: July 11, 2019, 02:12:18 PM »
If they are angular type of bearings, the front two take the thrust and the rear one keeps it in alignment radially.  It also provides a preload for the bearing stack when designed correct.  I bought a live center made in India to go with the 13" lathe I used to owned.  I could wiggle the center point up and down, but when I applied thrust to the point, it straighten up and ran true.  Never seen one made like that!

Most of mine are dumpster dive Rhone (sp) live centers that the center point was damaged.  Set them up on my T & C grinder and re-sharpen them.  They run good as new.  Oh, the bearings were in very good shape.  I have a couple of home made bull centers that just run on two bearings.  Because they are on two bearings, not double row bearings, they still wobble when holding a work piece.  Probable if I shimmed the bearings to give it a preload, the wobble would go away.
Ken

Carpenter84

Re: eBay accuracy humour
« Reply #4 on: July 11, 2019, 02:47:00 PM »
I think I could take a stab in the dark and say that Chinese $20 3 bearing center doesn't have angular contact bearings. Lol.
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

Bill Gruby

Re: eBay accuracy humour
« Reply #5 on: July 11, 2019, 02:51:04 PM »
 It may not be three, it could be a double row in front and a single in the rear position.

 "Billy G"
Don't sweat getting old, you'll still do dumb shit, just slower.

An Optimist will tell you the glass is half full, the pessimist half empty, the engineer will say the glass is twice as big as it needs to be.

Carpenter84

Re: eBay accuracy humour
« Reply #6 on: July 11, 2019, 02:56:24 PM »
Just a bunch of roll cages with washers for races? Lol
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

Carpenter84

Re: eBay accuracy humour
« Reply #7 on: July 11, 2019, 02:56:58 PM »
Hey... I'm still standing by my prediction of there just being 3 big balls rolling around a shaft.
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.