Key takeaways
- Use the gear or spline drawing, manufacturing route, critical zones, and downstream treatment plan to define the incoming bar order.
- Separate material-product conformity from tooth geometry, heat-treatment outcome, surface integrity, and finished-component validation.
- Specify decarburization and geometrical controls only with named methods, locations, process states, frequencies, and acceptance rules.
- Require every certificate and report to reconcile with the actual heat, process lot, blank or bundle, drawing revision, and release status.
Start from the component route
For gear, spline, or keyed-part routes, the RFQ should explain whether the steel bar is for rough machining, finished machining, heat treatment before machining, or later heat treatment by the buyer. The route affects size, condition, allowance, and inspection language.
Separate grade from condition
Grade names such as 40Cr, 42CrMo, 42CrMo4, or 4140 should be paired with the required delivery condition. Buyers should state whether annealed, normalized, QT, or another reviewed condition is expected instead of assuming the grade name defines the supply condition.
Clarify rough size and allowance
Gear and spline parts often require machining allowance around outside diameter, bore, face width, shoulder, or spline areas. The RFQ should separate rough bar size from final drawing size and identify the latest drawing revision where available.
Plan inspection for supplier review
Buyers should state chemical, mechanical, hardness, UT, dimensional, surface, or third-party inspection needs during supplier review when the part route is load-bearing, rotating, or drawing-controlled. Certificate and heat-number requirements should also be stated.
Translate the gear route into a bounded bar requirement
A gear or spline bar RFQ begins with the approved drawing and process plan, not a generic alloy grade. State the supplied stock envelope, finished section, tooth or spline manufacturing route, machining stock, critical transition zones, heat-treatment responsibility, surface finishing, and final inspection owner. ISO 683-2 supplies product and condition context for covered alloy steels but does not establish tooth geometry, case response, distortion, contact behavior, or component performance.
Assign each requirement to its acceptance stage
Use the matrix to avoid placing finished-gear requirements on an incoming-bar certificate or leaving critical downstream controls unowned.
| Decision | RFQ definition | Evidence required | Stage boundary |
|---|---|---|---|
| Incoming material | Grade, product standard, edition, product form, section, condition, surface, and alternatives | Inspection document with actual ordered results and heat or lot traceability | Evidence applies to the stated incoming or delivered bar state |
| Stock and geometry | Supplied and finished envelopes, datums, machining stock, straightness or form controls, and sample extent | Dimensional report using the controlled drawing and inspection stage | ISO 1101 language does not select tolerances or finished tooth acceptance |
| Surface and decarburization | Process state, functional zones, method, locations, frequency, permitted result, and disposition | ISO 3887 report where specifically ordered plus identity link | The method does not create an allowable depth or guarantee treatment response |
| Downstream release | Tooth manufacture, treatment, finishing, NDT, deviations, final validation, and release owners | Separate downstream records under the accepted process plan | Bar conformity does not certify the completed gear or spline |
Align drawing, material route, geometry stage, surface controls, downstream processing, evidence, deviations, and release ownership before manufacture. Only accepted order terms define the requirements for a specific supply.
Control stock removal, decarburization, and traceability
Show the supplied bar envelope and finished root, bore, shoulder, or spline zones on the drawing. Define minimum cleanup stock using approved geometry and tolerance analysis rather than a generic allowance. If straightness or other geometrical control affects machining yield, state the datum and verification stage. ISO 1101 provides geometrical-tolerancing language; the drawing and inspection plan must select the actual requirements and measurement approach.
Worked RFQ example for gear and spline bar stock
Attach both the supplied-stock schedule and the controlled finished drawing. Require suppliers to flag any conflict rather than choosing the more convenient interpretation.
Keep property and surface limits in the approved specification; placeholders should remain visible until the responsible engineer closes them.
Item: Alloy-steel bars or blanks for [gear or spline drawing and revision], [size and quantity]
Material: [grade] to [product standard and edition], [section, delivery condition, and surface]; alternatives by written clause comparison only
Geometry: Supplied and finished envelopes, datums, machining stock, straightness or form controls, end zones, and inspection stage per attached schedule
Process responsibility: [party] performs tooth or spline machining, heat treatment, finishing, NDT, and final validation; supplier lists every subcontractor
Surface control: Decarburization or other surface checks only to the named method, material state, locations, frequency, acceptance, and disposition
Documents: ISO 10474 type [state], actual results, heat-to-process-lot-to-blank-or-bundle map, dimensional and surface reports, and deviations
Release: Drawing conflicts and exceptions closed in writing before manufacture and shipment hold point cleared before dispatch
Only accepted order terms define the requirements for a specific supply.Steel bar RFQ checklist for gear and spline applications buyer questions
What should buyers include in a gear or spline steel bar RFQ?
Buyers should include intended component route, grade standard, delivery condition, rough bar size, final drawing size if available, machining allowance, heat-treatment expectation, inspection scope, certificate requirement, quantity, and destination.
Is grade name enough for gear and spline bar quotation?
No. Grade name should be paired with condition, size, machining route, drawing or final dimensions, inspection requirements, and document expectations so the supplier can review the bar route properly.
Which JOTAIN grades are often reviewed for gear or spline routes?
Depending on application requirements, buyers may review 40Cr, 42CrMo, 42CrMo4 / 4140, or 34CrNiMo6 routes. Final selection should be confirmed around load, size, condition, machining, and inspection needs.
Steel bar RFQ checklist for gear and spline applications RFQ checklist
- Component type such as gear blank, spline shaft, keyed shaft, sleeve, or machined rotating part
- Controlling grade standard and acceptable equivalent names if cross-reference is allowed
- Delivery condition such as annealed, normalized, QT, or buyer-reviewed heat-treatment route
- Rough bar diameter, length, machining allowance, and final drawing size where available
- Drawing revision, controlled dimensions, and mandatory notes that affect the quotation
- Hardness, mechanical property, or heat-treatment certificate requirement if applicable
- UT, dimensional, surface, or third-party inspection requirement before shipment
- Packing, marking, heat-number traceability, destination, and shipment document needs
- Gear or spline drawing revision, supplied and finished envelopes, critical zones, and duty concern
- Grade, product standard, edition, section, delivery condition, surface, and alternatives
- Datums, machining stock, geometry controls, end zones, measurement stage, and sample extent
- Tooth or spline machining, heat treatment, finishing, NDT, and validation responsibilities
- Decarburization need, method, material state, locations, frequency, acceptance, and disposition
- Heat and process-lot identity, actual-result documents, deviations, packing, and release
References
- ISO 683-2:2016 Alloy steels for quenching and tempering
Supports: Provides official product and delivery-condition context for covered alloy-steel bars used as incoming material routes.
Limitation: It does not define gear geometry, heat-treatment outcome, surface integrity, finished-component validation, or service suitability.
- ISO 3887:2023 Steels — Determination of the depth of decarburization
Supports: Defines methods for determining decarburization depth in steel products and components when the order requires examination.
Limitation: It does not choose an allowable depth, sample position, process state, frequency, removal rule, or gear acceptance criterion.
- ISO 1101:2017 Geometrical product specifications — Geometrical tolerancing
Supports: Provides standardized geometrical-tolerancing symbols and language used for drawing-based form, orientation, location, and run-out requirements.
Limitation: It does not select gear or bar tolerances, datums, machining stock, inspection stages, sampling, or measurement equipment.
- ISO 10474:2013 Steel and steel products — Inspection documents
Supports: Defines inspection-document types supplied to steel purchasers according to requirements established in the accepted order.
Limitation: A document type does not create missing tests, surface controls, geometry evidence, traceability depth, deviations, or release authority.
Revision note: Expanded the checklist into a stage-specific bar-to-gear procurement route with geometry and decarburization controls, one buyer table, two context figures, and a worked RFQ example.
Inquiry support
Send part route, grade, condition, inspection needs, and destination.
JOTAIN can review the stated grade, size, delivery condition, processing route, inspection requirements, and export details against the project requirement.