I've brought more than few bearings off VXB, not just 608's. 608's are
cheap because they're the most common bearing on the planet.
What you found is correct, it just means ABEC9 is machined closer to the
stated sizes of the bearing than the other sizes.
The run-out is not with the bearing itself, but after installed. A spindle
with ABEC-9 bearing should have less run-out than one with ABEC1, that is,
it will 'rattle' less. From that it'll spin faster with fewer problems.
Most machinery will have ABEC1 bearings because they don't spin all that
fast (< 30k RPM IIRC).
People see ABEC9 is a 'high-speed' bearing, and so think they'll go faster
with them in their skates. All that happens is their bank balance goes down
faster. I used to talk to a bloke who owned a skate shop, he gave up trying
to convince people they were wasting their money.
For guide rollers cheap is good enough as they don't have the same forces
operating on them as a spindle. I made a feed roller that was a board with
a bunch of 608's poking up out of it. Worked well, and cheap.
Don't get too wrapped up in precision, most things don't need it and it's
impossible to maintain on others (like wood).
Tony
> Tony, outstanding link.
>
> Thanks. The same bearings from McMaster Carr are twenty times the
> money. :-0
>
> Turns out the specs on the ABEC bearings has only to do with OD and ID,
> etc., nothing on runout I can find. Not that it matters much, really;
> I'll use bearings that are rigid and bearings that are spring loaded to
> oppose, and flat stock, and side bearings to maintain alignment, and it
> should work fine; the only thing I have to be careful to avoid is super
> fast bearings with "loose" balls, but that shouldn't be much of an
> issue.
>
> Best, Charlie
>
> --- In Homebrew_PCBs@yahoogroups.com, "Tony Smith" <ajsmith@...> wrote:
> >
> > > Hi Charlie,
> > >
> > > I would use skateboard bearings. They are available in ABEC7
> accuracy
> > > for very little money. Skate bearings are standard 608 size metric
> > > bearings, 8mm bore 22mm OD 7mm thick.
> >
> >
> > ABEC7 (in a skate shop) is a marketing gimmick. For skating you want
> 'crap'
> > bearings as free running is more important than run-out. That rating
> is for
> > high-speed spindles, hence the price. ABEC1 or 'precision' bearing
> are good
> > enough.
> >
> > The rating has nothing to do with quality either. Consider sealed
> (rubber)
> > instead of shielded (metal), they keep the dust out better.
> >
> > See www.vxb.com, they'll sell you 100 sealed bearings for $35.
> (Skates need
> > 16 bearings, boards 8, hence the odd pack sizes.)