Ball Bearings for tonearms

Ball bearings – the myth of ABEC quality

In the audio press and in advertising it is often mentioned that tonearm manufacturers are using best quality bearings, stating ABEC 7 quality. Does this statement have any practical use?

Let us check what an ABEC standard actually means. It is a US standard for classifying certain parameters of ball bearings. In this case it only guaranties that ball bearings are made to specific sizes and tolerances. The higher the number, the tighter tolerances of the bearing.

In any production process when parts are made, their dimensions have to be specified. It is almost impossible, for example to make a shaft exactly 20.000 mm in diameter. In production tolerances are used, which tell us how much bigger or smaller than the exact 20.000 mm the shaft can be. For example for that shaft to fit a hole of 20 mm in bearing housing, it would need to be smaller. The shaft can be made 0.1 mm smaller or only 0.01mm smaller. The smaller the size variation which is allowed, the tighter is the tolerance and the more difficult to make. The same applies for the hole size. It can be made bigger for 0.1 mm or 0.01 mm. I believe you get the picture.

ABEC standard ( US) or ISO ( European) prescribes only certain basic dimension tolerances of ball bearings. In ball bearings there is an outer and inner ring, balls and a cage which separates the balls. All these parts are made within certain tolerances to fit together and to be built into products.

ABEC and ISO standards do not cover: radial play, surface finish, material, ball complement, number, size or precision level, retainer type, lubrication, torque, cleanliness at assembly, raceway curvature, packaging and other factors that may be essential to the desired bearing performance.

I would like to emphasise a few of the most important parameters which are not covered by ABEC: Starting torque which affects the swinging of the tonearm up and down and following eccentricity of the record, noise level and vibration in bearings which adds distortion, cleanliness of oil which may restrict movements. It will not tell how precisely the ball bearings are fitted into the housing and shaft of the tonearm, which has direct influence on smooth zero play and movement of the tube in all directions and across the whole record playing area.

When you read about the quality of the ball bearings in a tonearms ask yourself ˝Did they choose the right bearings and are they fitted in the best possible way"? Just stating ABEC means the same as declaring that amplifier A is the best because it has the lowest measured distortion and, as we all know, this has nothing to do with good sound itself.