Foo - Uh oh... i think i screwed up on ebay

Okay well I just sold two ballscrews for 11 bucks each, same guy and all. I advertised them as what i believed them to be, 5/8 ROLLED ballscrew (rolled is pretty cheap, about 1.25 per inch). But i looked very carefully, and had another person look. It sure did not look rolled, but i did not think it was ground. Until i came across a picture of a true ground (very expensive and valuable) ballscrew. And these look identical....
So i think that what i sold, the guy believed it was 5/8 .2 rolled.
But now I am thinking its 16mm OD with a 5mm pitch, precision ground. The latter is MUCh more valuable, probably 5x the price.

So what do i do? I was thinking i would email the guy, let him know whats up. If he wants his money back, i will refund entirely. If he wants these screws, i will sell them to him at the same price.

Mistakes happen. Oh well. Sounds like a reasonable plan for handling the situation.

Well if they really are different from what you listed then you truly did make a mistake.
I feel you are not entitled to sell them to him. Do what you want, your call. Whatever you do, be decent about it.

Way too many aholes and rip off artists on Epay.

Just be nice about it all, you dont want negative feedback :o

If they will FUNCTION the same as the less valuable pieces, it is up to him whether to finish the purchase or not (and it sounds like he probably would, unless he's exceptionally nice to you). If they are not as good for some reason, then I'd still leave it up to him but explain that very carefully.

Basically either way I'd let him make the choice. If YOU decide to cancel the sale, he'd be justified in leaving you bad, or at least neutral, feedback (maybe he passed up other ones he could have bid on because he got yours).

Pretty much just inform him and let him decide...if you back down, you technically broke a contract, so it's best to get both sides to agree.

Consider this a lesson in thorough researh on an item before selling it. I've gotten some obscenely good deals on Ebay before, where the seller didn't know what something was worth and put a way too low buy it now price.

Go out and buy a pair of the screws you sold him and send them to him.

Then correctly list the ones you have.

Ok I am gonna show my ignorance.....What the hell is a ballscrew? :o

okay i explained. He was nice about it, said its no problem and he is only just beggining to gather components for a building his own CNC milling machine like 5bears.com
Impressive....

I refunded his money, he said we leave eachother positives

Ummm yeah, what's a ballscrew?

http://home.comcast.net/~phantomcow3/5821.JPG

Aaight I see it but I still have no idea what it is. Looks like a (heavy duty)piece of Allthread to me.

Well its a leadscrew. A leadscrew is used to control linear motion. So say you have a nut, and attached to the nut is a mug of coffee. THe nut is on a screw (any screw, allthread works too), and the screw is axially fixed. Meaning, it cannot be moved in any way except rotated.
Say the leadscrew is a piece of allthread 3/8-16, that means every the screw itself makes, the nut (and mug of coffee), moves 1/16 an inch.

THis is what a ballscrew is, a leadscrew. Now why its called a ballscrew...
Look at a piece of allthread, or acme rod if you happen to have some sitting around with a matching nut. When you have the screw traverse, there is friction. THe peaks that form the threads are sliding. So when one moves the nut, they have to overcome the friction of sliding elements.

But a ballscrew is different because it uses ball bearings. Ball bearings roll where a regular 60 degree rod would slide, so you have significantly less friction to overcome. THis makes the ballscrew a good 90% efficient, vs the acme or allthreads 30%ish. Because of the sliding, your regular threaded rod would generate a lot of heat if it was to be moving fast. Where a ballnut on a matching screw can move very quickly, with litlte heat buildup

Good explaination. :) Learn something new every day around here.