Thread: BALLS!...The race type
Ok experts and the like........My spindle head is sounding a little "Whizzy" in use. Sometimes it's there, sometimes it's not. I strongly suspect the ball races which are 7002 type.
So, my question is ...
Ceramic or not ?
Any benefits or gotchas ?
Will they withstand the occasional clamp/cutter interface etc
Or shall I stick to plain old metal sortIf you can't fix it with a hammer you've got an electrical problem !
Having worked with them for a few years in my day job my advise would be If you can afford the ceramic bearings then why not. Just be sure to get the accuracy and preload class correct. Contrary to common belief, they are as tough as the hardened steel ones.
Typically you will get the hybrid types on machines where the races are steel and the balls are silicon nitride or carbide. The balls actually condition the races somewhat and the whole system works smoother with less friction even at near dry conditions.
Best of luck.
Hmmmm....Preload and class. Well it's a Chinese build water cooled head. Unsure what the preloads would be but until I strip it (Work is busy at the mo and can't afford the downtime) I'll not know.
Perhaps I'll seek out some anyway and try them out.
Thanks for the reply
If you can't fix it with a hammer you've got an electrical problem !
Would suggest NOT going with ceramic's!
Why?, expensive and fragile!
A single "nock" or mishap could kill them and make it a waste of time for this application on top of it being OTT IMO.
Replace like-4-like and you cant go wrong.
Last edited by Lee Roberts; 05-03-2015 at 01:24 PM..Me
It depends on the ceramic used. (Engineering ceramics does not mean pottery) I can personally admit to having taken a hammer to some silicon nitride and silicon carbide balls and they did not even dent.
It all depends on what you buy.
I know of at least one oilwell drilling tool that uses such bearings being rated to a few hundred G's worth of shock.
One local manufacturer used to supply a machine reconditioner angular contact bearing for bridgeport type mill spindle. On my desk I have a set of angular contact bearings wheel bearings of the same brand as used on the racing Smart car made by the same company.
Please do not take this personally, I am just going on my experience. You may of course have different experience which I think would be nice to share here.
No problem and I stand informed/corrected my only experience is I once asked the same question and was given more or less the same reasponse by John Stevenson (John S).
Last edited by Lee Roberts; 05-03-2015 at 04:58 PM..Me
Cermic bearings do cost, but then if you go and buy any set of "precision" bearings you are bound to pay. Looking back, I purchased my steel ballscrew mounting moderate preload bearings for around the same price as I would have paid for the smart car ones. Ballscrew mounting rated ceramic ones were rather more expensive though as they had to be custom made and at the speed my screws were going to turn, it did not make sense.
Standard 7002's can be picked up relatively cheaply but then the runout will start to become a problem. Especially if you get ones that are not ABEC preloaded, I am thinking the ones that mountainbikes use (don't ask me where, all I know is I bought some from a mountainbike retailer at a good price). I used those with a 0.1 shim to preload and even then they were slack and gross.
For a spindle that makes money my view is to get the better value option, (performance/price).
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