Ordering a custom gear is not the same as ordering a standard catalog part. There is no shelf stock that matches your drawing, no tolerance class that everyone agrees on by default, and no single manufacturing route that is cheapest for every module, size and quantity. The custom gear manufacturing process is a sequence of controlled decisions, starting with your drawing or sample and ending with inspected, documented parts on your dock, and the quality of that sequence decides whether the gear runs quietly for ten years or fails in its first hundred hours.
The process starts long before the first chip is cut. When we receive a drawing in PDF, STEP or DWG, or a physical sample, our engineering team reviews it for manufacturability, not just for completeness. We check the tooth data, meaning the module or diametral pitch, number of teeth, pressure angle, helix angle, face width and profile shift, against the mounting bore, keyway or spline, and the required accuracy grade. We flag anything ambiguous, such as a drawing that says DIN 7 without stating whether that refers to the gear tolerance or the blank tolerance, and we confirm the heat treatment and the expected application. A strong RFQ speeds this up considerably: the most useful information is the gear's function and load, the input speed and expected torque, your preferred material or permission to recommend one, the required accuracy grade, the annual quantity, the number of pieces in this batch, and any inspection reports or material certificates you need.
The material sets the ceiling on the gear's strength, wear resistance and achievable cost, and it is chosen together with the heat treatment. For general-purpose industrial gears we most often start from 45 carbon steel, equivalent to AISI 1045, through-hardened to roughly 220 to 250 HB, or from 40Cr and 42CrMo, equivalent to AISI 5140 and 4140, for higher strength. Gears that must carry heavy shock loads in mesh are usually made from a carburizing grade such as 20CrMnTi, similar to 20MnCr5 or AISI 8620, which can be case-hardened to a 58 to 62 HRC wear surface with a tough, shock-resistant core. For corrosion-sensitive equipment we machine 304 and 316 stainless, and for low-cost, light-load motion we use brass or free-machining steel.
The blank is the foundation. Smaller gears are cut from rolled bar stock, while larger or higher-load gears are forged and then normalized to relieve forging stress. Turning brings the blank to the mounting bore, locating faces and outer diameter, and because every later operation references these faces, the bore and the runout of the locating surfaces are controlled before the teeth are ever cut. For one-piece shafts, where the pinion teeth and the shaft are integral, the same turning step also establishes the bearing journals.
Once the blank is ready, the teeth are cut, and the choice of process is driven by gear type, size, module and batch size, with a direct effect on price and lead time. Hobbing is the workhorse for external gears such as spur gears: a rotating hob cuts the teeth while the blank rotates in a coordinated feed, and one setup covers a wide module range. Gear shaping is used when the teeth sit inside a ring, between two flanges, or very close to a bearing shoulder that a hob cannot reach. Broaching is reserved for internal gears and splines in high volume, where it is fast per piece but needs dedicated tooling. Milling with a form cutter is the slowest route but the only practical option for one-offs, very large modules or non-standard tooth forms, because it requires no special tooling.
Heat treatment is what makes a gear durable, but it also moves the geometry. Through-hardening raises the bulk hardness and distorts the part only moderately, induction hardening selectively hardens the tooth flanks while leaving the core tough, and case carburizing produces a hard, wear-resistant surface of 58 to 62 HRC on a soft, shock-absorbing core, which is the standard choice for automotive and heavy-reducer gears. Nitriding gives a very hard, low-distortion surface but a shallower case, suited to high-precision, low-impact runs. The practical consequence for the buyer is that hardening must be followed by finishing whenever accuracy matters: heat treatment introduces slight tooth-to-tooth and profile deformation, and a gear cut to ISO 7 before hardening can easily move past ISO 9 afterward. This is why precision gears are allowed to distort and are then brought back to spec by grinding.
A gear's accuracy is stated per international standard, and the three systems buyers meet most often are close but not identical, so a drawing should always name the standard explicitly. For the majority of industrial gears, DIN or ISO grade 7 to 8 is the economical sweet spot: it is achievable with hobbing plus shaving or light grinding, and it is accurate enough for reducers, conveyors and machine tools. Grade 6 and tighter almost always requires gear grinding. After heat treatment the finishing options are grinding for the highest accuracy, honing for a smooth, quiet flank with a good contact pattern, and shaving as an economical pre-hardening finish. In AGMA terms the common industrial range is roughly Q7 to Q10, which maps across to DIN 8 down to DIN 6.
Quality is built in, but it is also proven. Every gear passes through in-process checks, such as blank runout after turning, tooth depth after hobbing and hardness after heat treatment, and a final inspection on a gear measuring center that records profile, lead, pitch and runout deviations against the drawing. Dimensional features are verified on a CMM or standard metrology equipment, and hardness is checked at the tooth flank and the core. For OEM orders we supply the documents procurement teams actually need: material mill certificates to EN 10204 3.1 that trace the heat number to the raw bar, an inspection report or COC listing the measured tooth accuracy and critical dimensions, and hardness or surface-treatment records where required.
Lead time depends on route and quantity rather than on the gear alone. A one-off prototype or a short-run set is typically ready in 7 to 15 working days once the drawing is confirmed, because the material is cut from stock and the setup is minimal. A small batch that needs heat treatment and light finishing usually takes 3 to 5 weeks, and a production order with dedicated tooling, carburizing and gear grinding lands around 6 to 10 weeks. The price is driven first by the quantity, because setup and tooling dominate small runs while material and cycle time dominate large ones, then by the tolerance grade, the heat treatment route, and the material, with special alloys and forged blanks carrying premiums. Parts are then preserved against corrosion and packed for ocean freight, individually oiled, wrapped in rust-preventive film and secured in export crates, so the gears reach you in the same condition they left inspection.
We are a Luoyang-based build-to-print gear shop running CNC hobbing, shaping, grinding, in-house heat treatment and a gear measuring center under one roof. That vertical integration is why we can hold DIN or ISO grade 6 to 8 accuracy, deliver prototypes in about two weeks, and trace every gear back to its raw material heat. Whether you need a handful of replacement spur gears, a matched set of gear shafts, or a production run of reducer gears, we review the drawing first and quote the most economical route that still meets your accuracy requirement.
On the practical questions buyers ask most often: to quote a custom gear we need your drawing or a physical sample, the quantity for this order and the annual volume, your preferred material, the required accuracy grade and heat treatment, and the application context of speed, load and environment. As for which grade to specify, for most industrial reducers and general machinery, DIN or ISO grade 8 as-hobbed or shaved is enough and most cost-effective; use grade 7 for high-speed or low-noise drives and grade 6 where gear grinding is expected, because holding a tighter grade than the application needs only adds cost and lead time.
If you have no drawing, we can reverse-engineer a sample gear, measure the tooth data and key dimensions, and produce a drawing for your confirmation before cutting, which is common for spare and legacy parts. A prototype cut from stock without special heat treatment is usually ready in 7 to 15 working days, with extra time for carburizing, grinding or forging and for international ocean freight. And on documentation, on request we supply EN 10204 3.1 mill certificates, a dimensional and tooth-accuracy inspection report, and hardness records, so tell us at RFQ stage which certificates your quality system requires.