Agricultural gears live a harder life than most industrial gears. They run in dust, mud and moisture, take shock loads when a plough hits a stone, and must be on the shelf before spring planting or autumn harvest. An OEM buyer who picks a supplier on unit price alone usually discovers the real cost in the field — a broken gear mid-season means a stopped machine, an angry farmer and a warranty claim. Sourcing agricultural gears is about specifying the right things and auditing the right capabilities.
The technical specification must be explicit. The mainstream material for transmission gears is carburising steel such as 20CrMnTi or 20CrMoH, carburised and quenched to 58–62 HRC with a case depth of 0.8–1.5 mm. Tolerance class for agricultural gears is typically IT7–IT8 — not as tight as a machine tool, but it must be consistent batch to batch. Module, tooth count, pressure angle and mounting distance should all be on the drawing, and the buyer should state whether the gear is for a new build or a spare-part replacement, because the acceptance criteria differ.
Packaging and rust protection are where many Chinese suppliers lose agricultural OEM orders. A gear may sit in a warehouse or on a ship for six to twelve months before it is assembled, and any rust on the tooth flank is a reject. The correct packaging is VCI (volatile corrosion inhibitor) paper inside, then a sealed bag, then a wooden or plywood crate with desiccant. Each gear should be individually wrapped, and the crate should be marked with part number, quantity and production date. Buyers who skip this detail get parts that look fine in the factory photo but arrive pitted at the dock.
When auditing a factory, four things matter more than the showroom. First, does the factory own its carburising furnace, or is heat treatment outsourced? Outsourced heat treatment is the single biggest source of inconsistent case depth and hardness in agricultural gears. Second, is there an in-house gear inspection centre with a gear tester and CMM, or does quality rely on a micrometer and visual check? Third, what is the capacity in the peak seasons — March to May and August to October — and can the factory run overtime without sacrificing quality? Fourth, ask for references from other agricultural machinery buyers, not just general industrial clients.
The common price trap is predictable. A low quote usually saves money on three things: a shallower carburised case, sampling instead of 100 percent inspection, and basic packaging without VCI paper. None of these shows up at incoming inspection; all of them show up six months later in the field, when a gear wears through or a tooth breaks under load. The unit price difference is typically 10–15 percent; the cost of a field failure and a warranty replacement is many times that.
At our factory we produce transmission and PTO gears for tractors, harvesters and implements, with our own carburising line and gear inspection centre. We ship every agricultural gear in VCI-wrapped individual packaging, and we can provide material certificates and hardness reports per batch. Send us your drawing and annual quantity, and we will tell you whether the specification is right for field use — and what the realistic peak-season delivery looks like.