Start With the Drawing Callouts That Drive the Route
A gear drawing carries a data table that decides most of the cost before you touch a rate sheet. Read module or diametral pitch, number of teeth, pressure angle, helix angle, face width, tooth thickness or over-pin dimension, and the required accuracy grade (AGMA 2015-1 A-grade or the older AGMA 2000 quality numbers, or ISO 1328). Then read the heat treat note (carburize to an effective case depth, core hardness, or induction harden) and whether the teeth are ground after hardening.
A Q8 or lower gear can often be finished by hobbing or shaving. A gear needing AGMA A3 or better after carburizing almost always needs a gear grinding operation, and that single callout can double the price.
- Accuracy grade and whether it applies before or after heat treat
- Case depth and hardness, which set the carburize cycle and stock allowance
- Lead crowning, profile modification and tip relief, which add grinder programming
- Bore, spline and keyway tolerances that force a finish-bore or honing step
Build the Cost Route Operation by Operation
Walk the router in the order the part will run. Saw or forge blank, rough turn, finish turn leaving grind stock, gear cut, deburr, heat treat, straighten or press quench correction if needed, finish bore and grind, tooth grind, clean, inspect, and pack. For each operation capture setup hours, run time per piece, machine rate and any tooling.
Hobbing and grinding setups are long compared with a lathe, so a lot of 10 carries a very different per-piece cost than a lot of 200. Quote quantity breaks explicitly. Hobs, grinding wheels and dressers are real consumables on high-volume work, and special profile hobs or form tools are NRE you either charge or amortize over a stated lot size.
Add Heat Treat, Distortion and Outside Processing
Most gear shops send carburizing, nitriding or induction hardening out, or run it in-house with a separate cost center. Either way, cost it as a per-pound or per-load charge plus testing (case depth cut-ups, microstructure, hardness). Then reserve a scrap and rework allowance for distortion: a carburized gear grows, shrinks and goes out of round in ways that depend on steel (8620, 4140, 9310, 16MnCr5), geometry and quench method.
020 inch of grind stock per flank, the grinder must remove it, and the more stock you add the more grind time and the more risk of grinding burn. Add outside processing such as shot peen, black oxide, phosphate or special NDT, with the vendor lead time noted on the quote.
Try it here, free
Custom Software Build Cost Estimator
Turn user roles, entities and screens, integrations, and authentication complexity into a realistic custom software build estimate with contingency included.
Include Inspection, Documentation and Margin
Gear inspection is not free and is often left out. A full lead, profile, pitch and runout check on a gear checker or CMM can take 30 to 90 minutes per part depending on tooth count and how many teeth are measured, and customers on aerospace or wind work may require every part or a sampling plan with a formal report. Add certification time (material certs, heat treat certs, CoC), first article work if the customer asks for AS9102, and packaging for finished gears.
Then apply overhead and margin on the sum, not on the labor alone. Compare the result to a similar past job in your ERP before releasing the quote, because the single best check on an estimate is the actual cost of the last comparable gear.
Where AI Fits in a Gear Quote
The slow part of gear estimating is reading the drawing and finding the last similar job. An AI assistant running over your ERP and drawing archive can pull the data table, flag the grade and heat treat callouts, retrieve prior jobs with the same module, tooth count and material, and draft the route with actual times and scrap rates for the estimator to approve. It does not replace the estimator's judgement on new geometry or an unusual quench, and it should not write a price into the ERP without sign-off.
If you quote fewer than a handful of custom gears a week and your estimator already knows every job, a spreadsheet may be enough.
Frequently asked questions
What is the biggest cost driver in a custom gear?
Usually the hard finishing path. A gear that is hobbed and shaved in the soft state is far cheaper than one that must be carburized and then ground to a tight AGMA accuracy grade. Gear grinding machines have high rates, long setups and wheel dressing costs, and distortion from heat treat raises scrap risk. Check the accuracy and heat treat callouts first.
How much grind stock should I leave on a carburized gear?
It depends on size, steel, heat treat method and the distortion history of the part family, so use your own data rather than a rule of thumb. Too little stock leaves ungrounded black spots after hardening, too much adds grind time and burn risk. Track measured stock removal and scrap by part family in the ERP and feed it back into the next quote.
Should gear shops quote setup separately from run time?
Yes. Hobbing, grinding and inspection setups are long relative to cycle time, so cost per piece swings sharply with lot size. Quote setup and run separately, price quantity breaks, and show NRE for special hobs or fixtures. That prevents a prototype lot of five from being priced like a run of five hundred.
Send Netray a sample gear drawing and a few past jobs and see a grounded draft route and cost build-up produced privately on your own data.