The core differences between granite square rulers and cast iron square rulers in precision measurement stem from essential disparitiesr dimensions: material physical properties, precision stability, usage and maintenance, and applicable scenarios, directly determining measurement reliability and long-term precision performance.
I. Material and Physical Properties ( Differences)
Granite Square Ruler (Primarily Jinan Blue / Mount Tai Blue)
Extremely strong stability: Aged naturally over millions of years, internal stresses are fuly released; no plastic deformation or creep.
Excellent thermal stability: Linear expansion coefficient of approximately 3×10⁻⁶/℃ (about 1/3 that of castwith minimal impact on precision from temperature fluctuations.
High hardness and wear resistance: Shore hardness HS70–80, 2–3 times higher than cast iron; resistant to ses and wears very slowly.
Non-magnetic and corrosion-resistant: No magnetic interference, rust-free, resistant to acids and alkalis; strong adaptability to humid/dusty environments.d vulnerable to impact: Edges easily chip or fracture upon collision; precision is irreparable, and damage renders it scrap.
Cast Iron Square Rulr (HT200–250 Grey Cast Iron)
Good rigidity and impact resistance: Possesses metallic toughness; slight collisions do not easily affect precision; can withstand certain impacts and heavy loads.
Average thermality: Linear expansion coefficient of approximately 11×10⁻⁶/℃; temperature changes easily cause precision drift, requiring a constant temperature environment.
Prone to rust and requirestection: Susceptible to rust in humid environments; must be regularly coated with rust-proof oil and stored in a dry place.
Precision is repairable: Surfaces can be restoredflatness and perpendicularity through scraping and grinding, offering a longer service life (8–15 years).
II. Precision Characteristics and Measurement Performance
Granite Square Ruler
High initil precision: Commonly Grade 00 and Grade 000; flatness/perpendicularity error can reach ≤0.005mm/m.
Strong precision retention: Noion required for normal use over 5–8 years; excellent long-term dimensional stability.
Surface characteristics: Ground surface with no oil reservoirs; high gloss and smooth movement, but eas affected by floating dust/impurities; strict cleaning required before measurement.
Cast Iron Square Ruler
Wide range of precision grades: Grade 00–Grade 2, withighest being Grade 00 (flatness ≤0.02mm/m).
Precision prone to fluctuation: Significantly affected by temperature, humidity, and vibration; requires frequent cion.
Surface characteristics: Scraped surface with tiny oil reservoirs; capable of accommodating minor impurities/oil films; stronger resistance to contamination, suitable for complex workshop environments.I. Usage and Maintenance
Granite Square Ruler
Extremely simple maintenance: No rust prevention or oiling required; only requires cleaning of the working surface and gentle handling.
Usage restrictns: Strictly prohibit collisions and heavy pressure; shock protection required during transportation/storage.
Weight: Approximately 20%–30% heavier than cast iron for the same specifications; ious to move.
Cast Iron Square Ruler
Complicated maintenance: Must be regularly rust-proofed (oiled) and stored in a dry place; re-protection required after cleaniexible usage: Impact-resistant and tolerates minor collisions; suitable for frequent use in workshops and heavy-load scenarios.
Weight: Relatively lighter; more convenient for transportation and installation.
IVomparison of Applicable Scenarios (Key to Selection)
Prioritize Granite Square Ruler
Ultra-Precision Measurement: CMMs, optical instruments, semiconductors / precision molds, metrology lab reference inspection
High Eronmental Fluctuations: No strict temperature control, high humidity, dusty workshops / on-site long-term measurement
High Long-Term Stability Requirement: Fixed reference tools requiring no frequent calion for over 5 years
Priority Selection: Cast Iron Square
General Workshop Inspection: Verticality / flatness inspection of machine tool guideways, tooling fixtures, and heavyworkpieces
Frequent Use, Prone to Bumps: High-frequency, rough measurement scenarios on the production floor
Limited Budget, Need for Long-Term Reuse: Repairable prelong service life, lower overall cost
V. Quick Overview of Core Differences
Table
Comparison Dimension Granite Square Cast Iron Square
Material Natural granite (inan Green) Gray cast iron (HT200–250)
Thermal Stability Excellent (Coefficient of linear expansion ≈3×10⁻⁶/(Coefficient of linear expansion ≈11×10⁻⁶/℃)
Accuracy Grade Grade 000, Grade 00 (Extremely hih) Grade 00–Grade 2 (High)
Accuracy Repair Non-repairable (chipped edges mean scrapping) Repairable by scraping, service lifeyears
Impact / Bump Resistance Poor (Brittle, prone to chipping) Good (Tough, minor bumps do not affect)
Rust / Maintenance No rust prevetion needed, extremely simple maintenance Must prevent rust, cumbersome maintenance
Surface Characteristics Grinding surface, no oil reservoir, susceptible to impurities Scraping surface, with oivoir, strong resistance to contamination
Applicable Scenarios Metrology lab, ultra-precision, long-term stability Workshop floor, general inspection, frequent use
Simple Summnite squares excel in “stability, accuracy, and maintenance-free” performance, suitable for high-precision and long-term stability scenarios; cast iron squares excel in “durability, rpairability, and low cost”, suitable for general workshop and frequent use scenarios.
