Square balers

How it works

A pickup lifts the crop and feeding forks or rotors push it into the side of the bale chamber. A plunger, driven by a heavy flywheel, slides back and forth along the chamber, and a knife on its face shears off each charge so it is packed in as a slice, or flake. Bale density is set by squeezing the walls at the back of the chamber, often with a hydraulic ram.

A toothed star wheel turns as the bale moves along and trips the knotters when it reaches the set length. Curved needles swing up through the chamber, bringing twine round the last side of the bale. In each knotter a rotating billhook ties the two ends, a knife cuts them, and the next plunger stroke pulls the knot tight. On big square balers a pre-chamber collects crop until a full, even charge is ready and then pushes it in all at once, which gives a better shaped, denser bale.

Main types

• Small conventional baler: Makes bales of about 36 by 46 cm in section and 85 to 100 cm long, tied with two strings and usually weighing 20 to 27 kg. Still popular with horse owners and small farms.
• Big square baler: Common bale sections are about 90 by 90 cm, 90 by 120 cm or 1 m by 1.2 m, up to around 3 m long, weighing roughly 450 to 1,000 kg. The plunger can press with hundreds of kilonewtons of force.
• Cutter or chopper models: Knives in the feed chop the crop shorter, which suits bedding and feed mixers and adds density.
• Throwers and accumulators: Small balers can throw bales into a trailer or drop them on a sledge in groups, cutting down hand work.

Hooking it up to a tractor

Square balers run offset to one side of the tractor on the drawbar so the tractor drives beside the row, and are driven by the PTO with a slip clutch or shear bolt to protect the drive. Small balers run happily on modest tractors. Big square balers are power hungry: Claas lists 270 hp as the minimum for its Quadrant 3400. Hydraulics and a cab monitor are needed for density control and pickup lift on most modern machines.

A short history

The Ann Arbor company built the first successful pickup balers in 1929. Arthur Young's Automaton baler of 1938 set the pattern for the automatic twine-tying baler and was taken up by New Holland, and Oliver brought out its own self-tying baler in 1949. The big square baler arrived when Hesston launched its machine in 1978. Small balers kept improving too: New Holland's plunger speed rose from 79 to 93 strokes a minute between its 326 and later models.

Buying and care tips

• Knotters first: Missed knots are the classic square baler headache. Check billhooks, twine discs and knives for wear, and use the twine the maker recommends.
• Plunger and knife: Look for play in the plunger rollers and keep the plunger and stationary knives sharp and correctly gapped.
• Drive protection: Check the slip clutch or shear bolt and the flywheel brake work properly; they save the gearbox.
• Bale count and service: Ask for the bale count on big balers, and look for fresh grease and oil rather than fresh paint.

Questions people ask

How much does a small square bale weigh?

Usually around 20 to 27 kg, though tight two-string bales of hay can be heavier.

Why does my baler miss knots?

Common causes are worn billhooks or twine discs, wrong twine tension, poor quality twine or the needles being out of time. Work through the maker's knotter setup guide.

Big square bales or round bales?

Big square bales stack and haul more neatly, which suits large livestock units and straw merchants. Round balers are cheaper and simpler and bales can be stored outside.

Related equipment

Sources

1. Baler (Wikipedia)
2. History of New Holland small square balers (Messick's)
3. Claas claims fastest rate for new big square baler (Farmers Weekly)

Last checked 2026-11-01

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