Chinese 300Hz spindle

[BartDeckers]

I recently bought one of the chinese spindles on e-bay.
http://www.ebay.com/itm/3KW-AIR-COOLED-SPINDLE-MOTOR-ENGRAVING-MILLING-GRIND-YVa-/260673870238?pt=LH_DefaultDomain_0&hash=item3cb15f999e

The spindle was advertised :
aircooled / 3 kW / 220 Volt / 0-400 Hz / 10-24.000 rpm

However I received a spindle with following specifications :
aircooled / 3 kW / 220 Volt / 300 Hz / 10 Amp

I contacted the seller to exchange the spindle for a 400 Hz unit. The seller now claims that the spindle can be used at 400 Hz "without any problem". I however am worried about possible damage to the bearings and the rotor.

I payed 292 USD for the spindle and 99 USD for shipping. Returning the spindle from Belgium to China will cost me 336 USD in shipping cost!

I think I will qualify for eBay Buyer Protection but before I go that lane I would value any opinion
or advise on this matter.

1) Do you think it is save or sensible to use this spindle at 400 Hz?

2) Will there be much difference in finish quality if working with 18.000 rpm or with 24.000 rpm? (I am not worried about speed of milling)

Thank you for your comments.

Bart

[bradm]

The finish quality is a function of the combination of spindle speed and feed rate. So, cutting at 18k rpm and 3 distance/timeperiod should have the same quality or lack thereof as cutting at 24k rpm and 4 distance/period.

At that price, I would expect the bearings in the spindle to be the same, regardless of what the numbers printed on the side say. Do you really want to ship it halfway around the world to have the numbers erased and reprinted?

I'd just use it. If it fails quick, complain and try to get help from ebay. If it fails after a few years, you got your money's worth, and you have almost established your replacement fund in the shipping savings.

[Gerald D]

The similar spindles from Italy, at a much higher price, have steel-balled bearings up to 18 000rpm (300Hz) and ceramic-balled bearings for faster.

Havn't heard that the Chinese supply ceramic-balled bearings in cheap spindles. As Brad indicates, if you make a fuss with the Chinese, they will probably change the label and no more.

[Kobus_Joubert]

You are lucky, mine looks the same and don't even have a label on it.....but it works.
I run it mostly at 12000 rpm...find it enough for most of my type of work.

[BartDeckers]

Brad,
So by reducing the speed I will be able to obtain a decent finish with 18.000rpm, that is no problem for me.

Gerald,
If I understand you well then none of the chinese spindles (not even the 400Hz ones) should be used above 18.000rpm due to the type of bearings used. Do you think that "warming up" the bearings at lower rpm's will help in prolonging the service life. I don't expect these cheap spindles to perform as HSD or Fimec but if carefull use may help?

Kobus,
Maybe I should be happy he didn't charge me for the label. :) It does bother me on the other hand that his (solar.jean) advertisment is misleading if not downright false.

[Kobus_Joubert]

Yes they are misleading in many way's...I had a problem with lovehappyshopping...that have changed name a few times on eBay...with the shipping costs.
But it is still a bargain. I have run my NO-LABEL 3kW ??? spindle at 400 hz that should be 24000 rpm without any problem.

[WTI]

Yes, warming up your spindle will make the bearings last longer.

When the steel bearings finally die, you can opt for ceramic replacements, but don't be surprised if the ceramics cost 1/2 the price of a brand new spindle.