{"id":3001,"date":"2026-06-27T09:43:49","date_gmt":"2026-06-27T01:43:49","guid":{"rendered":"https:\/\/jtlcnc.com\/?p=3001"},"modified":"2026-06-27T09:43:50","modified_gmt":"2026-06-27T01:43:50","slug":"what-is-the-achievable-flatness-of-a-high-precision-granite-machine-base-with-threaded-inserts","status":"publish","type":"post","link":"https:\/\/jtlcnc.com\/ar\/2026\/06\/27\/what-is-the-achievable-flatness-of-a-high-precision-granite-machine-base-with-threaded-inserts\/","title":{"rendered":"\u0645\u0627 \u0647\u0648 \u0645\u0633\u062a\u0648\u0649 \u0627\u0644\u0627\u0633\u062a\u0648\u0627\u0621 \u0627\u0644\u0630\u064a \u064a\u0645\u0643\u0646 \u062a\u062d\u0642\u064a\u0642\u0647 \u0644\u0642\u0627\u0639\u062f\u0629 \u0622\u0644\u0629 \u0645\u0635\u0646\u0648\u0639\u0629 \u0645\u0646 \u0627\u0644\u062c\u0631\u0627\u0646\u064a\u062a \u0639\u0627\u0644\u064a\u0629 \u0627\u0644\u062f\u0642\u0629 \u0648\u0645\u0632\u0648\u062f\u0629 \u0628\u0625\u062f\u062e\u0627\u0644\u0627\u062a \u0645\u0644\u0648\u0644\u0628\u0629\u061f"},"content":{"rendered":"

Flatness accuracy range of granite machine tool bases with threaded inserts:
Implementing the national standard GB\/T 20428-2006 “Granite Surface Plates”, divided into 4 accuracy grades. Due to the slight increase in machining difficulty caused by the drilling and embedding processes of pre-embedded stainless steel threaded inserts, the industry can actually stably achieve the following standards (tested at a constant temperature of 20\u00b0C):<\/p>\n\n\n\n

I. Upper limit of base flatness per meter for each grade (industry general simplified indicator)
Grade 000 (Top-tier ultra-precision machine tools)
Flatness error per meter \u2264 1.5 \u03bcm\/m
Applications: Wafer dicing machines, lens grinding machines, coordinate grinders, nano-optical equipment bases
Note: Small sizes (\u2264800mm) can stably meet the standard; for length\/width exceeding 1500mm or large areas densely populated with threaded inserts, most manufacturers relax the upper limit to 2.0 \u03bcm\/m.
Grade 00 (Mainstream precision machine tools)
Flatness error per meter \u2264 3.0 \u03bcm\/m
Applications: Micro-hole CNC, precision engraving machines, fully automatic vision measuring machines, multi-axis linear motion bases
The most commonly used grade for machine tool bases with grid threaded inserts, stable mass production is possible for both small and large sizes.
Grade 0 (General high-precision automated equipment)
Flatness error per meter \u2264 6.0 \u03bcm\/m
Applications: Conventional vision inspection, dispensing, screw-locking non-standard machine tool bases, lower cost.
Grade 1 (General tooling bases, rarely used for precision machine tools)
Flatness error per meter \u2264 12 \u03bcm\/m, not recommended for high-precision machining equipment.<\/p>\n\n\n\n

II. Complete calculation method for dimensions (precise tolerance of the national standard, not just per meter)
Total flatness tolerance (\u03bcm) = Grade coefficient \u00d7 Diagonal length (mm) \u00f7 1000
Grade 000 coefficient K=1
Grade 00 coefficient K=2
Example: 1000\u00d7800 base, diagonal \u2248 1280mm
Total flatness tolerance for Grade 000: 1280\u00f71000=1.28\u03bcm
Total flatness tolerance for Grade 00: 2\u00d71280\u00f71000=2.56\u03bcm<\/p>\n\n\n\n

III. Key notes on the impact of threaded inserts on flatness
Under the prerequisite of a qualified embedding process, the insert recess is 0.3~1mm below the surface, and the entire surface is ground at a constant temperature after completion, which will not lower the nominal flatness grade;
Limitations:
For bases with dimensions >2000mm and dense M10\/M12 heavy-duty threaded inserts across the entire surface, it is difficult to achieve Grade 000; Grade 00 is preferred;
If holes are too close to the edges, there are extremely many holes, or the base is thin (thickness <100mm), the flatness will be slightly worse, and the stone thickness needs to be increased to improve rigidity;
Process guarantee: Embed the inserts first and cure for over 72 hours before overall grinding to avoid later micro-deformation of the inserts destroying the flatness reference.<\/p>\n\n\n\n

IV. Accompanying Synchronous Precision (Additional Requirements for Machine Tool Bases)
In addition to flatness, machine tool bases typically include the following specifications:
Guide rail mounting surface straightness: \u22641.5\u03bcm\/m (Grade 00)
Threaded insert hole position accuracy: \u00b10.1mm
Working surface roughness Ra\u22640.32\u03bcm
Adjacent side perpendicularity: \u22642\u03bcm\/m
V. Selection Recommendations
Semiconductor, optical, and ultra-precision grinding machine tools: Grade 000 (small dimensions)
Precision CNC, image measuring, and multi-axis motion platforms: Grade 00 (optimal for general use)
Ordinary automated inspection fixtures: Grade 0, better cost-performance ratio<\/p>\n\n\n\n

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