Fly Presses and Screw Presses

Flywheel or Balls? A safety issue.
Kayne and Son #6 Manual Fly Press : Image (c) 2003 English Number #6 Fly Press : Image (c) 2003
Flywheel or Balls (weight arm), what is the difference?

Mechanically there is no difference. Both ways of suspending mass a distance from the center of the screw do exactly the same thing.

However, there are some practical differences. If mounted low on a bench the ball type can be very dangerous to anyone nearby. If the swinging iron ball were to strike someone in the head it would result in serious injury. The flywheel type have several advantages besides being safer.
  • The flywheel allows the operator to easily rotate the screw using the flywheel as a hand wheel from any position while making adjustments.

  • They also normally have several holes for the operating handle to screw into. This allows for easy adjustment of the lever position without removing and replacing the flywheel on the hex drive. These holes are usually not the same spacing as a six sided hex drive so it is possible to have even finer adjustment of the handle position.

  • The flywheel is sturdier than the weight arm and if overhead clearance is a problem the flywheel is much more compact.


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