Sickle Bar Mower Basics

The sickle bar mower is old technology that still earns its place on small farms, hobby acreage and rough ground. Learn how it cuts, what keeps it cutting, and how to run one safely.

Key points

A sickle bar shears stems between knife sections and guards, so sharpness and alignment matter most.
It suits small acreage, rough ground and modest tractors.
Keep a spare knife assembly and sharpen at the bench.
Always stop the engine, remove the key and wait for motion to stop before working on the bar.
Slow down when the crop is heavy or the bar starts to plug.

How does a sickle bar mower cut?

A sickle bar mower has a long bar with a row of fixed guards, and a knife with triangular sections slides back and forth across the guards. Each stroke shears the stems between a moving section and a fixed guard or ledger plate. It is a scissor action rather than the whacking action of a rotary blade.

That clean shearing is why a sharp, well-set sickle leaves an even stubble and uses little power. It is also why a dull or misaligned one starts to pull and tear and plug up.

Where does a sickle bar still make sense?

A sickle bar mower fits a five-acre homestead pasture, a small hay field of a few acres, fence lines, orchard rows with a mid-mount, and rough ditch banks. It works with modest tractor power and is easy to see and understand. Many are mounted on the three-point hitch or on the side of a tractor.

It is slower than a disc mower in heavy crop, and it will not tolerate sitting in a heavy lodged stand without good knife condition. If you cut many acres in one season, ask whether a disc mower is a better use of your time.

A five-acre homestead might only need one or two passes a year, so a spare knife and a small file in the shop is enough. A rancher cutting several fields will want several sharp spares and a regular schedule.

What does a sickle bar need before you start?

Do the walk-around with the tractor off and the key removed. Look at the guards for bends, the knife sections for chips and dull edges, and the knife head and pitman arm for wear. Check for loose bolts, and grease the fittings the manual shows.

The knife should move freely along the bar with the drive disconnected. If it binds, find out why before powering it.

Guards straight and not cracked
Sections sharp, riveted tight, none missing
Ledger plates in good shape where fitted
Knife hold-downs set so the knife is held snug but not binding
Pitman arm and bearings free of excess play
Safety shields and bar guards in place

How do you keep the knife registered and sharp?

Registration is the alignment of the knife with the guards at each end of the stroke. When the machine is correct, the knife sections sit centered in the guards at the end of the stroke, as shown in your operator's manual. If they are off, the bar will pull hard and cut poorly. Many mowers have an adjustment at the pitman or the bar mount to correct it.

Sharpen sections with a file or a grinder using the angle the manual specifies, and wear eye protection and gloves. Replace sections that are chipped, loose or ground thin. Many owners keep a spare knife assembly so they can swap in a sharp one in the field and resharpen at the bench.

How do you mow safely with a sickle bar?

The sickle bar's exposed knife is a serious cutting hazard even when it is still. Disengage the PTO and shut off the engine before touching anything on the bar. Keep children and bystanders well away, and never carry riders on the tractor.

Mow on slopes only as far as your tractor and the manual allow, drive up and down rather than across a steep face, and keep your ROPS up with the seat belt fastened. Walk the field first to find rocks, stumps, wire and holes, and mark the ones you cannot remove.

What are common problems and quick fixes?

If the mower plugs, look first at knife sharpness, then ground speed. Driving too fast for the crop is the most common reason for plugging. If the bar vibrates hard, check for loose bolts, a worn pitman or a bent knife head.

If cutting is ragged only in one spot, look for a bent guard or a chipped section there. After a strike on a rock or post, stop and inspect the bar before you keep going, because a small bend gets worse quickly.

Keep spare sections, rivets, guards and a pitman arm if parts for your older mower are hard to find. A short list of parts on the shelf beats a week of waiting while a good weather window closes.

When to get help: If the bar will not register, the pitman keeps breaking or you are unsure about slope limits for your tractor, ask the dealer service department or a qualified mechanic. Your extension office can help you decide what suits your acreage.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

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