Sourcing farm machine components to drawing from Chinese factories

Start from a controlled drawing

Buying a component to drawing works when the drawing carries every requirement the part must meet. A photo, a used sample or a brand part number gives a factory a starting point, but only a dimensioned drawing with a revision letter lets two suppliers quote the same thing and lets you reject a part that misses it.

Each drawing should state the material grade to a named standard, the heat treatment and the hardness required, the surface finish and coating, and the tolerances. Critical fits get their own tolerances. Everything else can fall under a general tolerance note: ISO 2768-1 sets four general tolerance classes for linear and angular dimensions without individual tolerances, for parts made by machining or formed from sheet metal, so a single class in the title block covers the uncritical sizes [2].

Most component makers in our parts and attachments section work this way. Send the drawing, name the revision on your purchase order, and ask the factory to quote against that revision.

Tillage wear parts: boron steel and hardness

Ploughshares, points, harrow tines and cultivator sweeps wear by abrasion against sand and stones while taking impact loads. Boron steels such as 30MnB5 are common for these parts, and a study at Eskişehir Osmangazi University found that quenching is essential for this steel in farm use: tempering lowered hardness, while a cryogenic step combined with tempering improved impact toughness [1]. The balance matters. A part that is too hard can crack on stones, and a part that is too soft wears out early.

So specify more than the steel name. State the grade, the hardness range and scale, where on the part hardness is measured, and whether the whole section or only the wearing edge is hardened. Ask for the quench and temper route and for any hard-facing or carbide inserts. Then compare quotes on the same basis.

Ningbo Hedi Machinery and Pacific, the trading name of Zhejiang Huashachi Machinery, both list forging among their production steps for wear parts. The Hedi boron-steel plough wear parts and the Pacific ZPM1X8 wear part show the type. When you copy a worn original, tell the factory, so it can rebuild the lost profile rather than copy the wear. These parts go on the machines in our tillage section and on the tractor implements that pull them.

Castings and housings

Cast gearbox housings, frames and brackets need a tolerance system written for castings. ISO 8062-3 provides one: dimensional casting tolerance grades, geometrical casting tolerance grades and required machining allowance grades, together with rules for indicating them on drawings and for rejection [3]. Putting the grades on the drawing tells a foundry how much variation is acceptable on as-cast surfaces and how much stock to leave for machining.

Name the iron or alloy grade, the minimum wall thickness and any pressure or leak test. Decide the supply stage too: a casting blank, a machined part with datums and bore positions defined, or a finished assembly with gears and bearings fitted. Jiashan North Machinery supplies cast parts for farm machinery, Allied Machinery makes precision castings and machined housings to customer drawings, and Yongkang Jingjiu casts and machines cylinder heads and blocks. If you would rather buy a finished drive, compare an assembly such as the Yingke YK-67 rototiller assembly against a bare housing plus your own gear set.

Crankshafts, gear cases, radiators and mufflers

Engine and drive parts carry functional requirements on top of dimensions. For a crankshaft, define journal and pin diameters with their tolerances, runout between main journals, surface hardness and hardened depth on the journals, thread and taper details at the shaft ends, and balance. Jinhua Fangyi Machinery lists crankshafts for small petrol engines, including one labelled for use in water pumps such as those from Zhejiang Leiya.

For a gear case, give input and output geometry, ratio, rotation, the lubricant and the bearing fits. Zhejiang Joyoung Machinery builds gear heads and cases, such as the Joyoung PGC0001 pole-saw gear case, and Zhejiang Yingke supplies clutch cases and gearboxes for garden machines.

For a radiator, state the core construction, mounting points, cap pressure and the leak test you expect. Zhejiang Hongyun lists copper-tin, copper expansion-tube and aluminium expansion-tube radiators for small diesel engines of the kind fitted to walking tractors.

For a muffler, give the engine variant, flange, outlet direction and permitted back pressure. If the machine is a portable tool sold where forest fire rules apply, ask about the spark arrester: SAE J335 sets test procedures for spark arrester exhaust systems on multiposition small engines under 19 kW, such as hand-held and backpack equipment [5]. Yuyao Xingjie General Machinery stamps mufflers for small engines used on the garden and forestry machines listed here.

First-article inspection and PPAP-style approval

Before production starts, approve the first parts made on production tooling. A first-article inspection report lists every characteristic on the drawing, numbered to match a marked-up copy, with the measured value and the result. Add the material certificate, the hardness report with test locations, and photos of markings and packaging.

The automotive Production Part Approval Process (PPAP), published by the Automotive Industry Action Group, sets out how a supplier shows that parts made during an actual production run, at production rate, consistently meet the design record and specification [4]. AIAG sells the manual in Chinese as well as English, so many Chinese plants already know its forms [4]. A full PPAP is more than most farm components need. A lighter package suits most agricultural parts: the drawing revision, dimensional results on several parts, material and hardness results, a process flow, a control plan for critical characteristics, and signed samples kept by both sides.

Holding the standard in production

Once samples are approved, agree on change control: the factory tells you before changing material, heat treatment, foundry or sub-supplier, and you issue a new drawing revision for any design change. Ask for a hardness and dimension report with each lot, and keep one approved sample on your shelf to compare against.

When you compare quotes, line up the drawing revision, material grade, hardness and test method, tolerance class, supply stage, inspection report and tooling cost. A low price on a different specification is a different part. For tractor driveline parts, Ningbo Benye also supplies components alongside its tractors.

Source notes

[1] Journal of Polytechnic (Politeknik Dergisi), Gazi University; authors F. Bozkurt, F. H. Çakır, Ü. Er (Eskişehir Osmangazi University) — Investigation of the Tribological and Mechanical Properties of Boron Steels in Terms of Potential Usage in Agricultural Applications, Vol. 24 No. 2, pp. 431-438 (2021-06-01) [2] SFS Finnish Standards Association (ISO distributor listing) — ISO 2768-1:1989 General tolerances - Part 1: Tolerances for linear and angular dimensions without individual tolerance indications (1989) [3] NSAI Standards shop (BSI publication) — BS EN ISO 8062-3:2007 General dimensional and geometrical tolerances and machining allowances for castings (2007 (BSI published 2010-01-31)) [4] Automotive Industry Action Group (AIAG) — PPAP-4 Production Part Approval Process (2006 (4th edition; page accessed 2026-11-06)) [5] SAE International — J335_202010 Multiposition Small Engine Exhaust System Fire Ignition Suppression (2020-10-06)