What does a rotary cutter do?
A rotary cutter uses one or more heavy blades spinning under a deck to cut tall grass, weeds and light brush that a finish mower cannot handle. It is driven by the tractor's power takeoff and usually mounts on the three-point hitch, though pull-behind models exist.
It leaves a rougher finish than a finish mower and is built for pasture, field edges, fence lines and overgrown ground. Know its limits: the maker's manual states what size of brush it can handle.
Read the manual for the specific cutter before first use. Different models differ in blade type, deck design and the way the driveline connects, and the manual is the authority.
How do you prepare the field first?
Walk the area before you cut. Look for rocks, stumps, wire, old fence, farm junk, holes, ditches and soft spots. Remove what you can and mark what you cannot, such as buried pipe or stumps, so you will remember them while working.
Check the weather and the ground too. Wet ground can bog the tractor and tear the sod. Also check for wildlife, such as ground-nesting birds or fawns hidden in tall grass, and think about whether this is the right time to cut. Your local wildlife agency or extension office can advise.
- Remove wire, metal and large rocks
- Mark stumps and hidden hazards
- Check gates and lanes for width
- Make sure people and animals are well away
- Look for hidden nests or young animals
What should you check on the machine?
Before each use, inspect the blades, blade bolts, deck, gearbox, driveline and shields. Chain guards or rubber flaps reduce thrown debris and must be intact. A missing guard is a reason to stop and repair before you cut.
Check the gearbox oil level and look for leaks. Grease fittings on the driveline and hitch points as the manual requires. Make sure the driveline shield turns freely and the PTO shaft is fully latched.
How do you cut at the right height and speed?
Set the deck height so blades clear the ground and stones. Cutting too low scalps the ground and picks up debris. The height depends on your goals, since pasture grass management may call for taller cutting than a roadside. Ask your extension office what works for your forage.
Match speed to the thickness of the growth. Heavy material needs a slower ground speed with the engine at the PTO speed the manual specifies. Forcing the mower through thick growth stalls blades and overloads the driveline.
Cut in a pattern that throws debris away from roads, buildings and animals. Plan your passes before you start rather than deciding as you go.
- Walk the pattern before starting
- Raise the deck for the first pass in tall growth
- Keep the engine at the PTO speed in the manual
- Slow down in thick patches
How do you work on slopes and around obstacles?
Slopes increase the risk of rollover, and a mower hanging behind can make things worse. Follow your tractor's manual on slope limits, and cut along patterns that keep you stable. Never turn sharply on a grade.
Slow down near trees, fences and ditches. Do not mow where you cannot see, and never mow close to a bank edge that may collapse. If an area is too steep, consider a different tool or a hired contractor.
If tall growth has covered the ground, a slow first pass at a higher setting, followed by a lower pass later, is safer for the machine and shows hazards before you reach them.
What are the biggest safety rules?
Keep everyone far away while the blades are turning, because objects can be thrown at high speed. Never let anyone ride on the tractor or mower. Stop the PTO before turning at the end of a pass if the manual says to.
Never clear a jam while the machine is running. Disengage the PTO, shut off the engine, remove the key and wait for the blades to stop completely. Wear hearing protection and eye protection.
- Disengage and stop before clearing anything
- Never step near the deck while running
- Keep the PTO shield in place
- Wear hearing protection
- Do not operate if bystanders are near
How do you care for it after use?
Clean off plant material and check for loose bolts, bent blades and cracks in the deck. Sharpen or replace blades in matched sets so the deck stays balanced. An unbalanced blade creates vibration that damages bearings and gearboxes.
Grease as required, and store the cutter lowered onto blocks and under cover if you can. Write down hours of use and any repairs for future reference.
Keep a spare set of blades and the proper bolts in the shop, so a bent blade does not end the day.
Key takeaways
- Walk and clear the field before cutting.
- Check blades, guards, gearbox and PTO shield every time.
- Set height and speed for the growth and your goals.
- Avoid slopes and bank edges where the tractor could roll.
- Stop everything and remove the key before clearing a jam.
Sources and further reading
Last reviewed: November 12, 2026. Written by the Rural Farm Life Editorial Team. See our editorial policy.