The geometry of the „cones“ used in cone- and-plate viscometers

Summary The geometry of eighteen cones used in two commercial cone- and-plate viscometers has been determined by measuring the profiles along four radii at right angles to each other. It is found that the cones are not truly conical and that there is considerable uncertainty in assigning a value to the cone angle and to the position of the apex. Large differences were also found between the calculated mean values and those quoted by the manufacturers. Thus the latter values should not be used without confirmation. The effect of these results on viscosity determination is discussed.