Don Pearce wrote:

I never found out what the right oil for a Garrard 401
was.
As the bearing is similar to a Roksan, according to the
pdf on that page,
then I guess the oil will be about right too.
I thought for a plain spindle on top of a ball-bearing,
something heavy like EP90 gear oil would be best.


I went the other way with my Thorens deck, and I used
sewing machine oil. Yes, I did need to top it up fairly
regularly, but it did *seem* to give less bearing noise
off the platter than a heavier oil.

I also tried PTFE spray once, but wasn't so keen.

Yes, it *is* actually important to use the right kind of
oil. The lubrication requirements of ball and plain
bearings
are different, so most car or bike oils are unsuitable.
The
problem here is that it's an odd application in a domestic
context. That's why the retail price is high.

Too thick, or too slippy like PTFE, STP, or molybdenum
disulphide, and the balls will skate. The surface of the
oil
will be wavy so it can be a choppy ride. If a ball catches
up with its own bow wave it may briefly lock and judder.
Pressure can be great enough to crack the casing, although
not at turntable speeds.

Too runny and it won't maintain a film.

If it absorbs moisture then corrosion-erosion will lead to
early failure.

You need a thin or medium single-grade, thixotropic (or
"clingy"), water repellent, corrosion-inhibiting machine
oil, I would think. Best option, unless you already have
some of the right kind of oil, is the recommended oil from
the manufacturer, if you can get it. Maybe expensive for
the
amount you get, but you'll only ever need a few drops.
Share
with friends.

A plain bearing would be quieter but an oil pump would be
a
problem, I suppose.


d You seem to be talking about a ball race, in which
caged balls roll
along a track. That isn't how these turntable bearings
work. A single
hardened ball bears against the centre of a hardened flat
plate. The
action is 100% sliding and there is no propensity for any
kind of wave
buildup. In a new bearing there is essentially a point
contact, which
demands high pressure lubrication - grease rather than oil
almost. As
the ball and plate wear, that very rapidly changes to a
small but
appreciable contact area that is supported adequately by
oil.

Ah, OK, thanks. That's more problematic. High pressure and
thick aren't related AFAIK. What's needed is high film
strength, and rapid replenishment should it break.

In which case I don't see the objection to a slippy additive
like teflon, unless the drive relies on drag for damping,
which is quite likely I suppose, or maybe such materials
aren't strong enough.

Otherwise the requirements are the same as I suggested. Are
both surfaces steel? Perhaps the pressure is so great that
the teflon, or PTFE, whatever, would puncture.

When I googled turntable bearing, I got every conceivable
configuration.

For such a small contact, the pressure is so great that most
kinds of grease will displace and leave it dry. A
thixotropic oil would maintain a little pool at the pressure
point, and one with a high affinity for itself and for the
metal would crawl up and maintain a film. Some slippy
additives might interfere with the crawling.

Why isn't the bearing assy in an oil-filled well?

Ian