| Granite Material Grade | Black, pink, red, and gray granite are commonly used for precision measuring tools. Material properties vary by quarry and batch. | Granite type, material certificate, density, water absorption, and batch information. | Compare the certificate with independent laboratory data or a third-party inspection report. | Material specification must match the approved quotation and technical drawing. |
| Working Surface Flatness | Precision grades are commonly specified in micrometres according to the ruler length and applicable inspection standard. | Flatness grade, inspection method, reference standard, and full inspection record. | Confirm measurement with a calibrated autocollimator, electronic level, or certified reference equipment. | Flatness tolerance should be stated numerically; avoid descriptions such as “high precision” without data. |
| Dimensional Tolerance | Overall length, width, height, hole position, and groove dimensions may require separate tolerances. | Dimensioned drawing showing tolerances for every critical feature. | Use a calibrated coordinate measuring machine, height gauge, or granite inspection equipment. | All critical dimensions must be traceable to the approved drawing. |
| Surface Finish | Precision granite surfaces are normally lapped or ground; the required finish depends on the application. | Surface-finish requirement, lapping process, edge treatment, and permitted cosmetic marks. | Inspect under controlled lighting and verify roughness where a numerical requirement is specified. | No chips, cracks, loose particles, deep scratches, or contamination on the working surface. |
| Customization Capability | Common options include non-standard lengths, threaded holes, T-slots, reference marks, supports, and protective packaging. | Engineering drawing, tooling charge, sample charge, revision procedure, and change-control process. | Request a drawing approval record and a pre-production sample or first-article inspection report. | Customization details should be confirmed in writing before production starts. |
| Minimum Order Quantity | Custom granite rulers are often quoted per piece or per project; standard items may have lower order requirements. | MOQ, price breaks, sample policy, and whether tooling or setup fees are refundable. | Compare the written quotation, proforma invoice, and final commercial terms. | All one-time and recurring charges should be listed separately. |
| Pricing Transparency | Price is influenced by granite type, size, precision grade, machining, inspection, packaging, and shipping terms. | Itemized pricing for product, customization, inspection, packaging, documentation, and freight. | Obtain at least three comparable quotations using the same drawing and delivery terms. | Compare total landed cost rather than product price alone. |
| Sample and First-Article Policy | Samples are useful for confirming material appearance, dimensions, surface quality, and packaging. | Sample lead time, sample cost, inspection scope, and approval procedure. | Measure the sample against the drawing and retain an approved reference sample or inspection record. | Mass production should not begin before written sample approval for customized orders. |
| Production Lead Time | Standard products may require a shorter schedule; customized and high-precision items usually need additional machining and inspection time. | Production days, inspection days, packaging date, and conditions that may affect the schedule. | Request a milestone schedule and compare it with production updates and inspection records. | Lead time should be defined from drawing approval or payment receipt, not stated vaguely. |
| Shipping and Delivery Terms | International orders may use EXW, FOB, CIF, or DAP terms. Heavy granite products require reinforced export packaging. | Incoterm, port or delivery address, shipping method, gross weight, dimensions, and insurance responsibility. | Check the commercial invoice, packing list, bill of lading, and packaging photographs. | Delivery responsibility and risk-transfer point must be clearly stated in the purchase contract. |
| Export Packaging | Suitable protection normally includes moisture control, shock absorption, reinforced wooden cases, and lifting instructions. | Packaging specification, case dimensions, gross weight, center-of-gravity marking, and handling labels. | Review packing photos before shipment and inspect the case and product immediately after arrival. | Packaging must protect the working surface and allow safe unloading with suitable lifting equipment. |
| Quality Inspection | Inspection may be performed by the supplier, buyer, or an independent third-party inspection agency. | Inspection plan, calibration certificates, test records, sampling method, and nonconformity procedure. | Verify calibration validity and request inspection records linked to the actual serial number or order. | Critical flatness and dimensional results should be recorded, not only marked as “passed.” |
| Documentation and Traceability | Useful documents include drawings, inspection reports, material certificates, packing lists, and certificates of conformity. | Document list, serial-number method, revision control, and record-retention period. | Match the serial number, drawing revision, inspection report, and shipping documents. | Each customized unit should be traceable to its production and inspection records. |
| Warranty Coverage | Warranty terms commonly address manufacturing defects, dimensional nonconformity, and agreed workmanship issues. | Warranty duration, exclusions, evidence requirements, replacement policy, and freight responsibility. | Ensure warranty terms are included in the contract rather than relying on informal messages. | Coverage should clearly distinguish manufacturing defects from damage caused by misuse or improper handling. |
| After-Sales Response | Effective support should include technical communication, claim review, corrective action, and replacement or repair coordination. | Response time, contact channel, claim procedure, corrective-action format, and spare-part or repair options. | Test the supplier’s response before ordering by sending technical questions and requesting a sample claim process. | Written response target: within 1–2 business days |
| Supplier Verification | A reliable supplier should provide consistent technical information, verifiable business documentation, and clear contractual terms. | Business registration details, factory or production-site evidence, references, audit records, and payment details. | Use video verification, site audits, third-party inspections, trade-document checks, and bank-account verification. | Do not approve a supplier based only on website content, low pricing, or unverified certificates. |
