Rotary feeders take a lot of abuse. Whether in fuel or wood chips, it seems like there are always abrasive contaminants, foreign objects, or seriously-oversized pieces in the material stream. Rotary feeder manufacturers and plant operators have tried many things to extend rotary feeder life under these challenging conditions.

What’s the best way to prolong feeder life?

Most people are surprised to learn that the #1 key to extending feeder life is taking care of a simple, relatively inexpensive component – the top knife.

A sharp feeder knife, like any kitchen knife or pocket knife, cuts better and with less effort than a dull knife.

Keeping a sharp knife in the rotary feeder assures a clean shearing action against the vanes of the rotor. Two benefits accrue:

  • Less torque is needed which extends the gearbox life
  • Power consumption will be reduced

A properly adjusted knife, set to the factory-recommended clearance from the rotor vanes, will actually reduce wear in the feeder barrel.

If the knife-to-rotor clearance is too wide, the rotor can wedge material between the rotor and the barrel. As the rotor turns, this wedged-tight material will grind on the chrome lining of the barrel as it gets pulled down through the housing by the rotor.

Given enough time, wedged material will create general wear or gouges in the barrel. The nature and depth of barrel wear is a key factor in the cost of rebuilding a feeder or even if a feeder can be rebuilt.

Maintaining The Rotary Feeder Knife

The best practice in rotary feeder maintenance is to inspect the condition of the knife and its adjustment once a week. Broken knives should be replaced immediately; knives with significant chips in the cutting edge are also candidates for replacement. Knife-to-rotor clearance should be checked and adjusted to factory-recommended clearances.

Knives are relatively inexpensive and, with training, easy to inspect and adjust. No operating practice or feeder upgrade provides a return-on-investment close to that of the proper management of the top knife.


If you’re interested in taking steps to extend the life of the rotary feeders in your plant, consider this roadmap:

  • Do a spot-check of the current knife-to-rotor clearances in your rotary feeder at your next down-day. A set of feeler gauges from 0.005” to 0.040” should be sufficient.
  • While you’re checking the clearance, take a few pictures or make some notes on the condition of the top knife.
  • Review the videos on the PMR rotary feeder Service page of Precision’s website if you need help with measurement or adjustment.
  • Contact our Applications and Sales Specialists here if you need to re-stock the knife inventory in your plant.

Knives: the surprising #1 key to extending rotary feeder life. Who would have guessed?


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