Complete Explanation of Precision Grades for Grooved Granite Platforms (Jinan Blue Granite, GB/T20428)
I. Core Conclusion First
Grooving ≠ direct downgrade, but grooving processing introduces precision risks; the final precision grade is determined by the data from re-grinding and re-testing after all grooving and tapping are completed.
Products on the market are divided into two main categories with distinct standards:
Standard Smooth Surface Inspection Plates: No grooving, few threaded holes, factory-calibrated directly to grade 000/00/0/1;
Custom Grooved Granite Bases (gantry bases, slide table mounting platforms in your picture): These are precision granite mechanical components and cannot simply follow the acceptance rules for standard plates.
II. Achievable Precision Grade Range
Using Jinan Blue granite as raw material, the following grades can be achieved under reasonable processes after completion:
✅ Grade 00 (Mainstream market precision for grooved bases)
The vast majority of linear motor platforms, gantry inspection equipment, and guide rail assembly reference grooved platforms use this grade.
✅ Grade 0
Ordinary vision equipment, standard module tooling grooved bases, with lower costs.
⚠️ Grade 000 is not recommended for arbitrary grooving
In principle, Grade 000 metrological reference plates should avoid large grooves and numerous deep holes; after grooving, internal stress is released, and flatness easily exceeds tolerances. If grooving is required, secondary precision grinding is mandatory, which is extremely costly.
❌ Misconception Correction: Many purchasers think “once grooved, only Grade 0 can be achieved,” but with proper processes, a stable Grade 00 grooved platform can still be produced after completion.
III. Why Grooving Easily Causes Precision Degradation?
Removing a large amount of material from the stone redistributes internal stress, causing slight distortion of the platform;
Micro-cracks easily form at the corners of grooves, and long-term temperature changes exacerbate deformation;
Grooving after only rough grinding without subsequent grinding causes flatness to directly exceed tolerances.
IV. To Maintain a Stable Grade 00 for Grooved Platforms, Process Requirements Must Be Specified in the Contract
Processing Sequence (Top Priority)
Rough machining of blank → Natural aging for 7-15 days → Grooving, drilling, and tapping → Overall secondary precision grinding → Final flatness re-testing and issuance of inspection report
❌ Pitfall to Avoid: Do not grind to precision first and then groove! The precision will most likely be scrapped after grooving.
Structural Design Constraints
Maintain sufficient wall thickness (≥60mm) between the groove and the platform edge to prevent edge collapse and deformation;
For long gantry through-grooves, avoid large-area excavation on one side to prevent asymmetric stress.
Acceptance Indicators Must Not Only Focus on Top Surface Flatness
Additional control for grooved equipment bases:
Flatness of the bottom surface of the guide rail mounting groove
Parallelism and perpendicularity between various mounting surfaces
It is not just about the precision of a single top surface.
V. Selection Scenario Reference
Linear motor gantry bases, high-precision guide rail inspection tooling
Requirement: Reach Grade 00 after completion; must require the manufacturer to perform secondary grinding after grooving and provide an inspection report.
Ordinary 2D vision equipment, standard screw module bases
Requirement: Reach Grade 0 after completion; preferred option for limited budgets.
Metrology room reference platforms, high-precision measuring tool comparison tables
Preferably select smooth-surface Grade 000 plates and avoid large-area grooving.
