What is the maximum diameter for branches stems, etc, that a chipper or shredder can take?

The maximum diameter of branches handled by individual chipper or shredders will be listed in the product manual and if you look through the product reviews each should list the maximum diameter to be handled by each machine. However, the maximum diameters tend to be as follows 

 

Electric Chippers or Shredders    – 30mm – 40mm or more

 

Petrol Chippers or Shredders      – 40 mm – 60mm or more

 

Professional Chippers or Shredders   – can be up to 100mm or more

 

NB: Large commercial models, used by tree surgeons and the forestry/lumber industry can have cutting diameters of 100mm-200mm upwards