Buyer context
Who this guide is written for.
OEM buyers, maintenance engineers, importers, repair workshops, and machinery factories sourcing shafts, pins, sleeves, rings, bearing accessories, brackets, and other drawing-based machined components.
Custom machined parts are often requested with a sentence like please quote according to the drawing. That can be enough for a first look, but it is not always enough for a reliable quote. The drawing may not show material substitution limits, heat-treatment route, critical datum, surface finish, inspection method, or whether the part is a one-time repair item or a repeat batch.
The supplier's job is not only to calculate machining time. The supplier has to understand which features control fit, which tolerances are critical, what can be measured after production, and whether any process such as hardening, grinding, coating, or plating changes the route.
A good RFQ makes the drawing usable. It separates confirmed requirements from open questions and gives the supplier enough context to price the same part the buyer expects to receive.
Product scope
Product scope this RFQ route can cover.
Mismatch risks
Where quotes usually go wrong.
The tolerance looks small but the function is not explained.
- Cause
- The drawing includes many dimensions, but the buyer does not mark which dimensions control fit or movement.
- Buyer loss
- The supplier may price unnecessary difficulty or miss the few dimensions that actually matter.
- Control
- Mark critical fit dimensions, datum faces, mating parts, and inspection method in the RFQ notes.
Material substitution is assumed.
- Cause
- The drawing lists a local or old material grade without saying whether equivalent material is acceptable.
- Buyer loss
- Suppliers may quote different materials, making price and performance comparison unclear.
- Control
- State the required material standard, acceptable equivalents, certificate requirement, and any prohibited substitutions.
Heat treatment changes the machining route.
- Cause
- Hardness, quenching, induction hardening, nitriding, or grinding requirements are not highlighted.
- Buyer loss
- The quote may miss a process step, or the part may not meet wear and fit expectations.
- Control
- List heat-treatment target, hardness range, hardened area, depth if required, and whether grinding follows treatment.
A worn sample conflicts with the drawing.
- Cause
- The buyer sends a used sample and a drawing, but does not say which source is authoritative.
- Buyer loss
- The supplier may copy wear, repair deformation, or an old revision instead of the intended part.
- Control
- Clarify whether the drawing, new sample, or measured sample controls production, and mark worn surfaces clearly.
Inspection is requested after the price is agreed.
- Cause
- The buyer asks for reports, material certificates, or third-party inspection only after quotation.
- Buyer loss
- Cost, lead time, and document scope change late in the order process.
- Control
- Add inspection points, report format, certificate need, and sample approval requirement in the first RFQ.
RFQ fields
Information to put in the first email.
| Scope | Send | Why it matters |
|---|---|---|
| Drawing files | 2D PDF, 3D file if available, revision number, units, scale notes, and whether the drawing is final or for review only. | The supplier needs a controlled file before deciding process route and quote basis. |
| Function and fit | Application position, mating part, load or movement condition, critical fit dimensions, and datum surfaces. | Machining review should focus on the features that control how the part works. |
| Material | Material grade, standard, acceptable equivalent, certificate need, and any surface or corrosion requirement. | Different material routes can change cost, availability, machining behavior, and final performance. |
| Heat treatment and finish | Hardness range, treatment area, case depth if needed, grinding or polishing requirement, coating, and surface roughness. | Heat treatment and finishing can change tolerance planning and production sequence. |
| Sample and measurement status | Sample photos, measured dimensions, worn areas, conflict between drawing and sample, and whether reverse engineering is needed. | A worn sample should not be copied blindly unless the buyer confirms the intent. |
| Quantity and approval | Prototype quantity, batch quantity, repeat demand, sample approval route, inspection report need, destination, and deadline. | One-off repair parts and repeat OEM parts can require different pricing and approval routes. |
Review route
How this RFQ should be cleaned up.
- Confirm the source of truth.Say whether the drawing, CAD file, sample, or measured sheet controls the quote. If there is a conflict, mark it before production review.
- Mark the critical dimensions.Every dimension matters on paper, but not every dimension controls installation. Highlight fit faces, holes, bores, shafts, threads, and datum points.
- Put material and heat treatment in the first email.These details can change process route, lead time, inspection method, and final price.
- Ask how the part will be inspected.A supplier should be able to say which dimensions, hardness points, and surface conditions can be checked before shipment.
- Separate prototype and batch expectations.A prototype quote may include setup and approval work. A batch quote should clarify repeat quantity and inspection rhythm.
Factory review points
Control points buyers should ask suppliers to check.
- Drawing revision, CAD availability, unit system, and production-source confirmation.
- Critical tolerance, datum face, mating part, and function review.
- Material grade, equivalent approval, certificate need, and stock or procurement route.
- Heat treatment, hardness area, grinding, coating, and surface finish confirmation.
- First-piece inspection, measurement report, sample approval, and batch inspection plan.
- Part marking, rust protection, packing, and destination requirement review.
FAQ
Common questions before sending this inquiry.
Can a supplier quote custom machined parts from a PDF drawing?
Yes, a PDF can start quotation. A 3D file, material note, critical dimensions, quantity, and inspection requirement make the quote more reliable.
What if I only have a worn sample?
Photos and measurements can start the review, but worn surfaces should be marked. The buyer should confirm whether to copy the sample or restore the original intended dimensions.
Should tolerances be simplified for quotation?
Do not remove important tolerances. Instead, mark the dimensions that control fit and ask the supplier to review manufacturability and inspection method.
When should heat treatment be discussed?
Discuss it in the first RFQ when hardness, wear resistance, surface depth, grinding, or dimensional stability matters. It can change both process route and price.