Where to get tungsten carbide bearing ball?

[potatoha]

I'm in the market for a new bearing ball for my deck.
Anybody know where to get 6mm, grade 3-10 tungsten carbide ball?

[YNWaN]

eBay:

http://www.ebay.co.uk/itm/6mm-Tungsten-Carbide-Lab-Planetary-High-Energy-Ball-Mill-Grinding-Ball-Media-/190844829936?pt=LH_DefaultDomain_0&hash=item2c6f3d00f0

However, it is likely that such a hard ball will grind into either the thrust plate, the spindle, or both.

[potatoha]

Thanks for the link Mark. I saw that one, too. I emailed them yesterday, but they don't know their geometric tolerances. I have been using tungsten carbide ball on tungsten carbide thrust plate for last 20+ years on my Elite Rock MKII and I recently noticed a pin head size dimple, approx. 0.5mm in diameter, on the thrust plate. I've changed the ball to a grade 10 chrome steel ball (about 60 HRc) but the sound changed as well. It sort of lost the clarity and focus a tiny tiny bit. The change in sound is really subtle but certainly noticeable. I may try something in between, like a Silicon Nitride perhaps?

[YNWaN]

The tolerances will be high on these balls as they are all made for pretty exacting applications. To be honest, the geometric tolerance isn't really an issue in this application as the ball doesn't rotate.

[PaulStewart]

My experience has been that both silicon nitride and tungsten carbide are best avoided in this application, both from a wear and a sound quality point of view. In my experience grade 10 chrome steel is the best all round solution, when combined with the correct lubricant.

Cheers

[The Grand Wazoo]

I was going to suggest that a good place to find one might be on the floor underneath the bearing of a turntable that had it's ball replaced with one, as there's a chance it might find a way out amid great swirls of swarf if the bearing wasn't designed to use one.
....but then I'd just be kidding.

[potatoha]

I believe the Rock's bearing was designed to use a tungsten carbide ball in fact. It only took 20 years to grind a 0.5mm dimple on the tungsten carbide thrust plate, so the wear wasn't so bad. Wouldn't it make sense to use the same material for both the ball and the thrust plate in terms of impedance matching I wonder? I took out the chrome steel ball after letting the platter running about three days non stop, fully lubricated of course, and found there's a tiny grey patch on the ball where it was in contact with the newly flattened thrust plate. I'm beginning to think that the life of the chrome steel ball would be much shorter than that of the tungsten carbide ball on tungsten carbide thrust plate.

[YNWaN]

The impedance match idea is a nice one except the bearing shaft won't be tungsten, ground tool steel more likely. However, with regard to which sounds better, I would trust your own ears - why wouldn't you?

Personally, I have been an advocate of magnetically supported bearings for some years. This technique, if done correctly, gives zero wear and measurably lower noise than any contact bearing.

[potatoha]

The impedance match idea is a nice one except the bearing shaft won't be tungsten, ground tool steel more likely. However, with regard to which sounds better, I would trust your own ears - why wouldn't you?


Townshend's bearing shaft does look like a composite of steel with WC thrust pad brazed on top of it. I just miss the old sound of WC ball.
Until I could find a source for a high grade WC ball, I might try a grade 5 Si3N4 ball for now. They are so cheap these days, I can't resist temptation. :)



Personally, I have been an advocate of magnetically supported bearings for some years. This technique, if done correctly, gives zero wear and measurably lower noise than any contact bearing.
Is one in the making Mark?

[YNWaN]

Is one in the making Mark?

I've built a number for myself and use one in my deck now - a lightly different one will be fitted to the new deck I am working on.
They need to be matched to the mass of the platter so one isn't a universal fit.

[Qwin]

Mark - does a magnetic bearing not de-couple the platter from the acoustic chain?

Thats if you believe in it? I used to, but I'm not to sure anymore.

I run a parallel tracking arm which has a sled sliding back and forth on an air cusion, this de-couples the cartridge/wand from the arm/plinth so breakes the chain and according to the theory should sound pants. Trouble is it sounds great. :scratch:

[potatoha]

Mark - does a magnetic bearing not de-couple the platter from the acoustic chain?

Thats if you believe in it? I used to, but I'm not to sure anymore.

I run a parallel tracking arm which has a sled sliding back and forth on an air cusion, this de-couples the cartridge/wand from the arm/plinth so breakes the chain and according to the theory should sound pants. Trouble is it sounds great. :scratch:

I don't think a magnetic bearing would de-couple the platter entirely. I don't know about Mark's but magnetic bearing assemblies such as Clearaudio, Verdier, de Paravicini, etc. are all implemented around common contact bearing designs. In these examples, magnets reduce the stress of the bearing under load by reducing the contact points' elastic deformation. By doing so, the size of the contact patch become smaller, thus it may reduce the wear and the level of vibration/standing waves caused by the elements in contact. I would be surprised if there's any turntable bearing with complete magnetic decoupling.

[The Black Adder]

Would a Delrin ball bearing be any good? I had one for my Gyro, twas good! :)

[potatoha]

Would a Delrin ball bearing be any good? I had one for my Gyro, twas good! :)

Delrin balls come in better grade surface finish, but they are harder (R119-122) and have much much lower elastic modulus than WC, so I think it would be worse in terms of wear on the contact elements??? I could be wrong.

[YNWaN]

It is true that some magnetic bearings use the magnetic force to partially support the weight of the platter but there are decks where the platter is entirely supported and the bearing shaft makes no contact with a thrust pad - mine is such a design.

Yes, it is true that such a design means that the 'closed loop' is broken. However, the bearing is still held in the lateral plane and my own bearing is heavily viscous coupled - the platter certainly does not bounce on the magnetic field that supports it.

To be honest, my experiments in this area have led me to seriously question the validity of the closed loop concept - I seriously doubt that any turntable bearing is equally rigid across the audio spectrum anyway.

[YNWaN]

I've heard some designers claim that the vertical contact point of the bearing 'earths' the vibration in the platter. Whilst this is a nice idea I don't think it is supported by closer inspection. If the platter and chassis are connected in this manner the platter vibration (energy) is coupled to the chassis - to which the arm is mounted. If you measure vibration

[nat8808]

Why would having a connected loop be desirable anyway?

That surely ensures that unwanted vibrations and resonances are exchanged between them. All you want is for everything to remain in position relative to each other..

It might be difficult to de-couple and keep the relative positions solid but it does not therefore logically follow that it's desirable to have a "closed loop". I would guess that that idea has been proliferated via simplicity of communication to the consumer with catchphrases rather than bothering to go into detail of the real world situation.

[YNWaN]

If you measure vibration

Oh, I got distracted by the arrival of a friend. I think I was going to say -if you measure the vibration present on the surface of the platter and than on the surface of the armboard/chassis - the armboard/chassis is significantly greater.