Fawick Electric Clutch Settings

The Fawick type of clutch was the most common electric clutch used for High Speed in the headstock of Model 41B and 42B machines.  Lucas altered the operating air gaps of the clutch after receipt from the clutch manufacturer. Here are the pertinent specifications.

Model  Fawick P/N  Lucas P/N  Fawick Original Gap  Lucas Gap

Model Fawick P/N Lucas P/N Fawick Original Gap Lucas Gap
41B SC650 905856 0.016 0.009
42B SC775 905857 0.018 0.010



These ‘Gap’ settings must be performed with the clutch energized with full, correct voltage and represent the gap remaining before the magnet is completely ‘seated’. These new gap settings result in the clutch achieving a wider spacing between the clutch plates when the clutch operating voltage is removed.

Operating the clutch with the Original Clutch Manufacturer settings may result in the machine tool Spindle rotating even when the machine has been successfully shifted into Neutral due to ‘drag’ between the released clutch plates.  This may pose a personnel hazard.

Other Fawick Clutch data:

Model Fawick P/N Lucas P/N DC Volts Ohms Amps Watts
41B SC650 905856 90 140 0.642 58
42B SC775 905857 90 90 1.00 90


The most practical manner of setting the gaps is to connect the clutch to the machine tool power supply, rather than to a separate power supply to assure that the power supply used in actual operation will operate the clutch in a correct and safe manner.

The most practical method of installing the clutch into the machine tool is to connect temporary, extended length wiring between the usual clutch connecting wires and the clutch.  These temporary wires should be threaded thru the machine casting following the same route that the final wiring will follow.  The entire gear and bearing assembly that drives the center of the clutch should be removed from the machine and installed into the clutch while the clutch is ‘on the bench’.  After the gear and bearing assembly, is installed, the clutch should be energized and the entire assembly of clutch, driver gear and bearings should be loaded into the machine as a single unit.  While the assembly is being installed into the machine, the extension wires are drawn backwards through the casting.  After the assembly is fully ‘seated’ and secured onto the machine shaft, the clutch should be de-energized and the temporary extension wiring removed.

This is the only known means of positive assurance that the clutch driver gear is properly and fully inserted into the clutch.  The gear and bearing assembly will be ‘held’ in place by the magnetic field of the clutch while the assembly is installed into the machine. Since this process involved working with an energized electrical device, it is IMPERATIVE that all connections be properly insulated; that protective, insulated gloves be worn and that any other safety measures be taken that appear to be needed.  Lucas Precision is NOT responsible for any damage or personnel injury resulting from using this procedure.  The preceding text is explanatory only and outlines a process that has been used previously to install the described clutches.  The description should not be construed to be an endorsement of that procedure.  How YOU load the clutch and what safety precautions YOU do (or don’t) use are YOUR concern.

The clutch vendor states that the most practical means of determining clutch plate wear is to examine the spiral groves on the face of the clutch plates.  When the spiral grooves have 'disappeared' on any one plate - the entire stack of clutch plates should be replaced or the entire clutch replaced. It is normally expected that 3 or 4 adjustments of the operating air gap will be required before the clutch plates have achieved an amount of wear sufficient to require their replacement.  Lucas Precision does NOT stock replacement clutch plates although we do attempt to keep a complete clutch in stock.  It is our experience that by the time replacement clutch plates are needed, there is usually more wrong with the clutch than only the plates since the High Speed clutch on Models 41B and 42B are never engaged while the clutch is rotating and thus receives only minimum plate wear.

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