Start with the final rod route
Straightness and surface condition should be discussed around the final use: piston rod, cylinder rod, guide rod, linear-motion part, machined blank, or chrome-plating-prepared rod.
Surface route language
State whether the requirement is black bar, peeled bar, ground bar, polished bar, machined blank, or material prepared for further finishing. Each route has different size and surface expectations.
Straightness and tolerance details
If straightness, runout, diameter tolerance, surface roughness, or final machining dimensions are controlled by a drawing, attach the drawing or state the key values with the request.
Inspection before shipment
Inspection discussion may include dimensional checks, surface condition, straightness, heat number traceability, MTC, UT if specified, third-party inspection, packing, and destination.
Specify the rod state and functional zone
Hydraulic-rod procurement often mixes base bar, machined blank, plated rod, and finished component language. Separate those states first. Identify which party owns heat treatment, straightening, grinding, polishing, coating, and final inspection. On the drawing, mark seal-travel, bearing, thread, and machining zones and state which surface remains functional. A straightness statement without the inspected state or evaluated length can be met at one stage and lost at another. Likewise, a roughness result on an uncoated blank cannot confirm the finished coating surface.
For a sealing zone, retain the roughness parameter and measurement setup with the result. NIST documents the roles of profile filtering, probe geometry and evaluation length. Use comparable settings when reviewing pre-coating and finished-rod records, while keeping the drawing’s limits specific to each manufacturing stage. [5]
Measurements to settle in the RFQ
| Characteristic | Purchaser must define | Quotation evidence |
|---|---|---|
| Diameter | Basic size, limit system or clear limits, measured rod state, and controlled zones | Offered tolerance basis, method, temperature basis where relevant, and sampling |
| Straightness | Tolerance-zone meaning, evaluated length, datums or free-state setup, and end exclusions | Support arrangement, rotation or scan method, locations, and reporting format |
| Surface texture | ISO 21920 parameter, limit, direction, evaluation settings, and functional zones | Instrument method, trace locations, filtering settings, and result record |
| Surface condition | Permitted indications, handling damage rule, coating state, and person approving the lot action | Visual inspection stage, coverage, repair proposal, and deviation handling |
RFQ example
Item: Hydraulic-rod blank to drawing [number and revision]
Supply state: [base bar / machined blank / plated rod] after [last supplier-controlled operation]
Material: [grade, product standard, edition, and delivery condition]
Diameter: [basic size and ISO 286-2 class or clear limits] on zones [identify]
Straightness: Drawing callout to ISO 1101:2017 with [evaluated length, datum or free-state setup, support, end exclusions, and reporting]
Surface texture: ISO 21920-1:2021 indication using [parameter, limit, direction, and evaluation settings] on seal-travel zone
Inspection: Supplier to state equipment, locations, sampling unit, corrective-straightening rule, and final reinspection stage
Certificate: ISO 10474 document type [state type] with actual listed dimensional and surface records
Questions buyers ask
Why should hydraulic rod RFQs mention straightness?
Straightness affects downstream machining, grinding, polishing, chrome-plating preparation, assembly review, and inspection planning. If the project controls straightness, include the requirement with the inquiry.
Which surface conditions should buyers specify for rod bars?
Buyers may specify black, peeled, ground, polished, machined, or chrome-plating-prepared routes depending on final use, tolerance, surface expectation, inspection needs, certificate wording, and downstream processing.
How should buyers specify straightness for hydraulic rods?
State straightness tolerance if known, final rod function, bar diameter, length, surface route, downstream machining or plating plan, inspection method, certificate needs, and whether the requirement applies before or after processing.
RFQ checklist
- Rod type and final application
- Required grade standard and delivery condition
- Rough diameter, final diameter, length, and quantity
- Surface route: black, peeled, ground, polished, machined, or plating-prepared
- Straightness, tolerance, roughness, or drawing-controlled details
- Dimensional, surface, MTC, traceability, UT, or third-party inspection needs
- Packing, destination, and downstream process notes
- Identify whether the inquiry covers base bar, machined blank, plated rod, or finished component.
- Mark every diameter, straightness, texture, and surface-condition zone on the drawing.
- State the final supplier-controlled operation before acceptance measurement.
- Review support, end exclusion, rotation, sampling, and reporting methods before order.
- Include post-inspection protection and packing in the release checklist.
References
- ISO 1101:2017 — Geometrical product specifications — Geometrical tolerancing
- ISO 286-2:2010 — ISO code system for tolerances on linear sizes — Part 2
- ISO 21920-1:2021 — Surface texture: Profile — Part 1: Indication of surface texture
- ISO 10474:2013 — Steel and steel products — Inspection documents
- Vorburger et al.: NIST roughness calibration and measurement uncertainty
Inquiry support
Working from a part drawing?
Send the drawing or RFQ with the grade, size, condition, processing, inspection, quantity, and destination. We can flag open points before quotation.