Re: Ball screws

Posted by

on 2014-06-07 10:36:15 UTC

Let me add to this discussion on the Chinese ball screw supplier suggestion. In early Nov 2013 I ordered a ball screw from a supplier in China via ebay. Supermario-au was the listed seller. My desire was to get a 800mm long BS in 20mm diameter with a Left Hand threads with a flanged ball nut. Since LH ball screw components are not listed on your standard cheap BS ebay supplier pages I messaged several suppliers asking if a LH thread was available, After several messages back and forth with one of the suppliers with pictures and diagrams of what a LH pitch screw would look like, I was finally quoted a price and ordered one 800mm 20mm diameter with machined ends for $80 shipped. 6 weeks later, I received a RH thread ball screw with un-machined ends. Therefore the part I got would not fit my application. After several more messages back and forth including one that suggested that I just convert it or install it backwards I was finally apparent that they could not supply what I wanted and would refund my money if I returned the ball screw. This did not happen until I opened a formal complaint with paypal. Guess what, shipping charges to China is a lot more expensive then shipping from China must be because the cheapest option was via International US post. Approximately $62 dollars to return a 80 dollar ball screw. I complained to paypal again who ruled in my favor about the shipping cost saying it was not worth $62 to return a $80 item since I'd net only $18 dollars in the the long run. Luckily Paypal then paid for the shipping and I shipped it back. I was watching the tracking back to the source via the USPS webpage and it seemed to stall in LA customs and is still there. Now add more phone calls to the postal service and another 8 weeks of waiting for the postal trace and it's still the same. I should make a few more calls to the Postal service to see if I can recover the loss insurance from the postal service. I'm NOT hopeful. I've more or less given up and have wrote off the loss of the $80 and called it an experience I never want to have again. I'll Not buy from Chinese based suppliers again. I've tried twice and have gotten burned twice. First time was a video recorder that never arrived, but I did get a refund so that tuned out OK

In short I'll sum this up. Chinese sales people are barely able to understand typed English and have little to no understanding of what they are selling. And if there is a problem terrible rude customer service that will NOT stand behind the 100% satisfaction guarantee shown via their ebay listings. Yes there are shose who have had satisfactory results. For you Great. For me, I'm done with CHINESE direct PERIOD.

---In CAD_CAM_EDM_DRO@yahoogroups.com, <garyclick@...> wrote :

Recently ran into a case where very cheap bearings were using "Case Hardened" or surface hardened balls and races. Look the same, under very light loads perform the same BUT they are not the same. By the way, did I say they were really cheap. Running in a metal saw these failed in a week or so with the back of the blade slicing into the outer race of the bearing. When replaced with conventional bearings and run for a comparable amount of time there is no sign of a groove or wear , just a shiny band where the blade back is running.

I have designed a lot of specialty machined used in our factories over the last 40 years. Depending upon the application, I have used Acme Screws, Acme Screws with counter loaded nuts, rolled ball screws, precision ball screws and ulta-precision ball screws up to 4" in diameter and 27 feet long. The trick is to determine what quality (= price) you need and don't over spend. No sense putting an Ball Screw on a hopper that levels to 1/2" or and Acme Screw on an axis that must repeat to +/-.002 in 10ft (didn't say accurate). Either way you will eventually be disappointed.

As was well stated, "you get what you pay for". The trick is determining what you really need pay for. Precision ground ball screws might be a little bit of over kill on a wooden frame router for example. Good rolled ball screws or even Acme Screws could keep you happy for years. On thing that will not make you happy is frequently failures and replacements

nitewatchman

From: CAD_CAM_EDM_DRO@yahoogroups.com [mailto: CAD_CAM_EDM_DRO@yahoogroups.com ]
Sent: Tuesday, June 03, 2014 7:03 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Ball screws

I have owned lots of "quality" lower price items and now am able to afford the "overpriced" big names.

You can kid yourself all you want, there is a difference. With Chinese stuff it is usually not how it works when new, it is how fast it needs replacement.

Buy cheap, buy twice. There is a reason it is cheap.

That is not to say that for a specific use the cheaper item is not a good choice, just to point out that there is nothing for free. Better materials, better heat treat, better balls. It all adds up to more money. But for a hobby machine that might only get 100 hours of use a year cheap is probably a great solution.

Tim Goldstein

A2Z Corp

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