Drive Nuts and Chucks
Whip Mix driving motors provide two basic speeds. High speed at 1725 rpm is recommended only for vacuum-investing with the 200 mL or 300 mL Vac-U-Spat. Because of its small paddle diameter, the Vac-U-Spat gives the most uniform results with all inlay investments with high speed spatulation.
Low speed at 425 rpm is recommended for all Vac-U-Mixers when spatulating gypsum materials, alginates and large quantities of investments. The Power Mixer with Vacuum provides only low speed. But the Combination Unit has two drive speeds: the rear Drive Chuck #6108 is the high speed at 1725 rpm, and front is the low speed at 425 rpm. Drive Nuts on the mixing units and corresponding drive chucks on motors have been designed to prevent the interchange of a mixing unit between these two speeds.
Also, the directions of rotation of the drive chucks for these speeds is opposite. The high speed drive chucks of the discontinued Vac-U-Vestor and the Combination Unit require a Left-Hand thread for the paddle shaft and drive nut. The low speed drives of the Combination Unit, and the Power Mixer with Vacuum, need a Right-Hand thread for the paddle shaft and drive nut.
It is important, therefore, that the proper drive nut is specified whenever a mixing unit is ordered. And when adapting a mixer already in use the thread direction must be considered — sometimes the entire paddle assembly must be changed.