BEARINGS MATERIAL – WHICH TO USE

NOTE: Several different scales are used to determine the hardness of various materials used to make bearings. So, the comparisons below are approximations.

Carbon Steel – Used for low-grade bearings, has a hardness of about 4 on a scale of 1 to 10.

Chrome Alloy Steel – Used for higher-grade bearings, has a hardness of about 7 and a very fine grain structure. These are the bearings normally installed in the Microsoft trackballs.

Tungsten Carbide – Carbide is extremely tough with a hardness of about 9. But alas, it has a relatively coarse grain structure. It is made of particles held together with a ‘binder’ substance. The ‘grain’ depends on the size of the particles and the binder substance and is usually coarser than tool steel. When installed in a trackball, the ball may not turn as easily and the carbide crystalline grain may wear/damage the surface of the ball quite quickly.

Ceramics – Ceramics in general are about as hard as carbide and have a very fine and smooth grain structure.

Logitech has been using ceramic bearings for over ten years (I believe it is alumina oxide – ivory or light tan in color). I have Logitech Trackman FX’s that I have used for about that long with no sign of wear on the bearings and the ball turns as freely as when it was new – as long as I keep it clean.

Ceramic bearings are about as durable as tungsten carbide. The hardness of the two materials is measured on different scales, making it difficult to make a direct comparison.

Zirconia Oxide – The hardest mineral is diamond with a hardness of 10 on a 1 to 10 scale. Zirconia oxide made from zirconium, the mineral used to manufacture man-made diamonds has a hardness of about 9. Zirconia oxide (white in color) has the highest strength and toughness at room temperature of all the advanced ceramic materials. The very fine grain size allows for extremely smooth surfaces. It is more costly than alumina oxide and tungsten carbide but the advantages are worth the extra cost for use in trackballs.

TRACKBALLS R US

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