11 Gear Processing Steps You Need to Know

Step 1 is the blank. For a shaft gear, we cut bar stock to length on a bandsaw and face both ends. For a disc gear, we saw plate or, at higher volumes, drop-forge a near-net blank so the teeth are not cut from solid. The blank decision drives everything downstream: a forged blank leaves less material for the hob, but you pay for tooling and you wait longer for first parts.

Step 2 is datum turning. A gear lives or dies by its bore and face runout. We turn the bore, one face, and a reference diameter in a single setup so the tooth-cutting operations have something true to hold. On a 27-tooth pinion with a 40 mm bore, we aim for ±0.005 mm on the bore and 0.01 mm total runout on the face. A gear cut from a soft, badly turned blank will show it later as noise.

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  Saw and faceBar or plate cut to length, both ends square.
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  Forge near-netHigher volumes, less hob stock, tooling cost up front.
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  Turn the datumBore and face in one setup for true runout.

Step 3 is hobbing. A hob is a rotating cutter that generates the tooth form as the blank indexes. It is the fastest way to cut external spur and helical gears, and it handles a wide module range. Hobbing leaves a visible feed mark on the flank, so it is usually a pre-finishing operation. On our 4,000 mm maximum processing size, large ring gears are hobbed on a horizontal machine with the table indexed through the cut.

Step 4 is shaping. When a gear sits next to a shoulder, or the teeth are internal, a hob cannot reach. A pinion cutter reciprocates and generates the profile, so shaping reaches internal splines, cluster gears and parts with a close shoulder. Shaping is slower than hobbing, and the cutter cost is higher, but for an internal gear it is often the only practical route.

Step 5 is shaving. A rotary shaving cutter removes a few microns from the flank and corrects lead and profile errors left by hobbing. Shaving is a soft operation, so it runs before heat treatment. It buys you a quieter gear, and it is common on automotive transmission gears where noise matters. On a small batch, shaving may not pay for itself; on 10,000+ part runs, it usually does.

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  HobbingExternal spur and helical, fast, leaves feed marks.
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  ShapingInternal teeth, shoulders, cluster gears.
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  ShavingSoft finishing, corrects lead and profile.

Step 6 is heat treatment. Case carburizing puts a hard skin on the flanks while the core stays tough. Through-hardening is used where the whole section needs to be hard. Heat treatment moves the part: a 100 mm gear can grow or warp by tens of microns, and the bore may no longer be round. That movement is why finishing steps come after, not before.

Step 7 is hard turning. Once the gear is hard, we turn the bore and faces again on a machine that can handle the hardness. This restores the datum that heat treatment disturbed, so the tooth flank and the bore share one axis. Hard turning replaces some grinding, and it is faster, but it cannot match ground flank quality on every profile.

Step 8 is grinding. For gears that need tight lead and profile after hardening, we grind the flanks. Grinding also fixes the bore and faces where the tolerance is tighter than hard turning can hold. On a medical or aerospace gear, grinding is often the last metal-cutting step before inspection.

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  Case carburizeHard skin, tough core, part grows.
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  Hard turnRestore bore and face datum after heat.
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  GrindTight lead and profile on hard flanks.

Step 9 is surface finishing. A gear may need black oxide, electroless nickel or bead blasting. Each one changes the flank by a micron or so, so it goes on after the final cut and before measurement. Laser marking for a part number goes on last; minimum character height is 1.5 mm so it stays readable after coating.

Step 10 is inspection. We check the bore, face runout, tooth thickness, lead and profile against the drawing. A raw material check runs at the start, in-process monitoring runs through the cuts, and final inspection signs off before the part leaves. Reports are available on request. 100% inspection before shipment is standard for gear work.

Step 11 is packing and shipping. Gears are oiled, wrapped and boxed so the flanks do not touch in transit. We ship parts in 3–5 days once production starts, and we can start production within 24 hours of a released order. If you send a drawing today, you get a quotation and a free DFM analysis within 12 hours.

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  FinishBlack oxide, nickel, blast; marking last.
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  InspectBore, runout, tooth thickness, lead, profile.
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  ShipOiled, wrapped, boxed; 3–5 day ship.