01Single shaft, double shaft or four shaft
Double shaft shredders shear bulky material into strips without a screen. Single shaft machines use a pusher against one rotor and a screen, which sets output size. Four shaft machines add sizing to the shear. Ask which output you need, not which is bigger.
02Blade thickness, steel and hardness
Blade thickness sets strip width on a double shaft machine. Ask the steel grade, the hardness, and whether blades can be reground or have to be replaced.
03Drive and reversing control
Shredders reverse when they stall. Ask whether the drive is hydraulic or electric, whether the gearbox is sized for the shock, and how the control detects overload.
04Feed and output handling
A hopper, a pusher or a ram, a discharge conveyor and a magnet may or may not be in the offer. Count them.
05Wear parts per tonne
Blades, spacers, screens and bearings wear. Ask for the expected life on a named material and the price of one full blade set.