Axial or Inline gearboxes refer to such types as Helical, Shaft mounted, or planetary designs.
These gearboxes are very common choices for most industrial applications due to their robust nature, high permissible radial forces, closely stepped ratios and low backlash.
Helical gearboxes can typically be found in applications requiring high permissible radial force, stepped ratios and low backlash.
Shaft-mounted or otherwise known as Parallel shaft gearboxes provide an inline option with a versatile and space saving foot print. This is the only inline gearbox version with the option of a hollow output shaft.
Planetary gearboxes are usually chosen for high tech, high torque, high speed applications requiring extreme accuracy.