Gear Cutting Cost: Quoting Hobbing, Shaping and Grinding

Gears are one of the few parts that arrive at the cutting machine already expensive. The blank has been turned, bored and often heat-treated before a single tooth is cut, so the value sitting on the table is high before the real work starts — and the real work is slow, tooling-heavy and unforgiving of an error in module or tooth count. Gear cutting cost doesn't behave like a milling job priced on stock removal. It's driven by the gear's geometry and quality class, the process the geometry forces on you, and a tool — hob, shaper cutter or grinding wheel — that wears and has to be amortized across every tooth it touches.

This guide builds a gear unit price the disciplined way — blank, setup, cutting cycle, tooling amortization, secondary operations, inspection, overhead and margin — but with the details that separate hobbing, shaping and gear grinding so the number you quote survives the first-article gear inspection and the production run behind it.

Why gear cutting doesn't price like milling

On a mill you remove a defined volume of stock and the cost tracks cycle time across that removal. On a gear cutter the cost tracks something else: the number of teeth, the module, the helix, and the quality class the print demands. A 120-tooth gear isn't "twice" a 60-tooth gear — every tooth is an indexed generating cut, so cycle time climbs with tooth count, face width and the number of passes the class requires.

Three things make gear cutting its own cost category. First, the blank already carries turning, boring and sometimes heat-treat value, so scrap on the gear cutter is expensive scrap. Second, the cutting tool is a precision consumable — a hob or shaper cutter is reground a finite number of times and amortized per tooth, not bought per job. Third, the high-quality gears almost always need a second generating operation after heat treat: gear grinding or honing to recover the distortion the furnace introduced. The skeleton is the same as any CNC machined part — the line items underneath are what change.

The three processes: hobbing, shaping and grinding

The first question on any gear quote is which process the geometry and the quality class force, because each has a different cost profile.

Process	What it does best	Cost driver
Hobbing	External spur and helical gears, splines	Tooth count × face width × passes; hob life
Shaping	Internal gears, cluster gears, shouldered	Stroke rate, indexing, shaper-cutter wear
Gear grinding	Hardened gears, high quality class (≤ DIN 6)	Stock per flank, passes, wheel + dressing

Hobbing is the workhorse for external gears: the hob and blank rotate in a continuous generating motion, so it's fast and the cost per tooth is low once running. Shaping wins where a hob physically can't reach — internal ring gears, gears next to a shoulder, cluster gears — but it's a reciprocating, indexed cut, so it's slower and the cutter is fussier. Gear grinding is the precision finisher: a hardened gear that must hold a tight quality class after heat treat is ground flank by flank, slow and consumable-heavy, the same way a precision shaft ends up on a cylindrical grinder. Matching process to geometry and class is half the quote.

What drives the cost of a gear-cutting line

Five ingredients set the cutting cost on a gear. Estimate each one and the line builds itself.

1. Module (or DP) and pressure angle — sets the tool, the chip load and how much metal each tooth removes.
2. Number of teeth and face width — the cycle scales with both; more teeth and wider faces mean more indexed generating time.
3. Quality class — DIN/AGMA class drives pass count, feed and whether grinding is required at all. A DIN 8 gear may hob complete; a DIN 5 gear must be ground.
4. Material and heat-treat state — a soft blank hobs quickly; a case-hardened gear needs grinding after the furnace and a tougher wheel.
5. Tooling amortization — hob price ÷ regrinds ÷ teeth-per-regrind, or grinding wheel + dressing spread per part. This is a real per-part cost, not overhead.

Quote a hardened DIN 5 ring gear as if it hobs complete and you'll miss the entire grinding operation; quote a soft DIN 9 spur gear as if it needs grinding and you'll lose the job to a shop that read the class correctly.

Quality class: the callout that decides the process

The gear quality class — DIN 3962 / ISO 1328 or AGMA — is the single line on the print that decides whether you have a one-operation job or a three-operation job. A loose class (DIN 8–9, AGMA 8–9) can often be hobbed or shaped to final on a soft blank and shipped. Tighten to DIN 5–6 and the route changes completely: cut soft and oversize, heat treat, then grind or hone the flanks back into class. That's two extra operations and a wheel cost on a part that already carries all its upstream value.

Reading that callout correctly is the estimate. The same discipline applies to every tolerance on the print — profile and lead tolerance, runout, tooth-to-tooth and accumulated pitch error all translate into machine time and scrap allowance, the way the GD&T-for-estimators guide treats geometric callouts on any part. Get the class wrong and the unit price is wrong before a margin ever touches it.

Setup, tooling and the secondary operations nobody itemizes

Gear setup is heavy and fixed per job: mount and centre the blank, set the hob or shaper cutter, dial the change gears or CNC parameters for the ratio and helix, cut and inspect a first-off gear over pins or by span measurement. On a ground gear, dressing the wheel to the right profile and proving it out adds its own block of fixed time.

Because setup is divided by the batch, the per-part number swings hard with quantity:

Batch size	Setup cost (€240 total)	Setup per part
1	€240	€240.00
10	€240	€24.00
50	€240	€4.80
250	€240	€0.96

Then there are the operations that hide between cutting and inspection: chamfering and deburring the tooth tips (a real, often manual operation on every gear), heat treat for hardened gears, and the gear inspection itself — over-pins or span measurement at minimum, a gear-checker run for tight classes. List each as a line so it sits in cost, not in margin, the same way a complete manufacturing quote template forces every job to carry its real operations.

A worked example: a hardened helical gear, batch of 50

Take a 20MnCr5 helical gear, module 2.5, 40 teeth, 25 mm face, case-hardened, quality class DIN 6 — so it cuts soft, heat treats, then grinds. Quantity 50, on a €95/h burdened gear-machine rate.

1. Blank — turned and bored gear blank: €11.00 each.
2. Setup — hobbing setup €240 ÷ 50 = €4.80.
3. Hobbing cycle — generate 40 teeth ≈ 4.0 min at €95/h = €6.33.
4. Chamfer + deburr — tooth-tip chamfer and edge break ≈ 1.5 min = €2.38.
5. Heat treat — case-harden, allocated per part ≈ €6.50.
6. Gear grinding — grind both flanks to DIN 6 ≈ 5.0 min at €110/h + wheel share = €10.20.
7. Inspection + scrap allowance — over-pins/gear-check + ~4% scrap on a high-value part ≈ €2.80.
8. Cost per part = 11.00 + 4.80 + 6.33 + 2.38 + 6.50 + 10.20 + 2.80 = €44.01.
9. Price at 35% margin — using price = cost ÷ (1 − margin), 44.01 ÷ 0.65 = €67.71.

Push the batch to 250 and setup falls to €0.96, cost drops to roughly €40.17, and the same 35% margin gives €61.80 — the quantity break a buyer expects, defensible line by line. The margin step uses the same arithmetic as any job; if dividing by 0.65 versus multiplying by 1.35 ever trips you up, the margin-versus-markup guide settles it, and the burdened rate behind every minute above comes from your shop hourly rate calculation.

From a drawing to a gear price

The slow, error-prone part of gear cutting cost estimation isn't the arithmetic — it's reading the drawing completely under deadline: module or DP, tooth count, helix and pressure angle, the quality class and the profile/lead/runout tolerances that decide whether the gear ships off the hob or has to be cut soft, hardened and ground. Miss the class and you've mis-priced the whole route before a margin lands.

QuoteBuddy reads the technical drawing and surfaces those features — gear data, quality class, tolerances and the operations the geometry implies — so the estimator builds the price from a complete picture instead of a hurried scan. The cost engine then assembles blank, setup, cutting cycle, tooling, secondary operations, inspection and your target margin the same way every time, on every gear.

Start a 30-day trial and run a few real gear drawings through it — from upload to a complete, itemized quote PDF — and see whether the gear price it builds matches what you'd have quoted by feel, with the margin landing exactly where you set it.