NOTE 7: I think this is the biggest source of potential errors in a frequency analyzer. I've run tests which indicate that from very light to very heavy clamping pressures might cause as much as 6cpm variation on raw steel shafts. I obtained a two or three cpm variation with graphite shafts as the clamping pressure increased over a broad range. The only way I know of controlling the exact pressure on the shaft is to use some kind of controlled application of force independent of displacement such as an air cylinder. Most analyzers use a torque screw, as do the Club Scouts, or a toggle clamp. The torque screw has a clutch that slips when a certain torque on the screw is reached. The force applied by a toggle clamp is totally a function of how it's set up. Obviously a toggle clamp can be set such that it can almost crush the shaft. The force applied by the torque screw is related to the slip clutch setting and more importantly the friction in the system. It's the friction in the system times the force applied that must equal the torque applied. The Club Scout slips at about a foot pound of torque. The force applied to the clamp times the friction in the threads ultimately must balance this torque. The bolt, which applies the pressure in the Club Scout, is lubricated to keep the friction to a minimum and thereby maximize uniform force on the shaft. If the bolt were contaminated with grit for instance it would take very little force before the clutch would slip. The torque screw approach has the advantage of always applying a reasonably constant force regardless of the thickness of the shaft. The Club Scout clamp applies about 500 pounds of force to the shaft.
The variation of applied force has the biggest impact on a gripped club. The harder the grip is clamped the less damping it will generate. The less damping the higher the frequency. Some toggle clamping systems on the market can put so much force on the grip that its dampening effect is significantly reduced.(Be careful when you clamp a raw big butt shaft with a toggle clamp.)