Grinding Machine Accuracy Inspection

⌖How to inspect

• Check the flatness and parallelism of the magnetic chuck faceFlat surface

  ToolsDial indicator or test indicator (move the table and trace the surface)

  ProcedureTrace the chuck face with the indicator and see how the height changes lengthwise and widthwise. If it is out of tolerance, regrind it (see the Wheel Care section)

  TolerancesKaneteck's quality standard for electromagnetic chucks: for a face plate with length or diameter of 300 mm or less, flatness 0.01 mm and parallelism 0.02 mm; over 300 up to 600, 0.015 and 0.03; over 600 up to 900, 0.02 and 0.04; over 900, 0.025 and 0.05. Surface roughness 6.3S

  Kaneteck's standard also covers attractive force (average 98.1 N or more, 49 N or more at the weakest point), dielectric strength (AC 1500 V for 1 minute), insulation resistance (5 MΩ or more, 500 V insulation resistance tester), temperature rise (15℃ or less, energized for 3 hours) and water resistance

  ^[29][30]

• Measure the thickness and parallelism of a trial-ground workpiece (working accuracy)Flat surface

  ToolsOutside micrometer, dial indicator with 1/1000 mm minimum graduation and stand, granite surface plate

  ProcedurePlace the ground workpiece on a granite surface plate and measure the thickness with a micrometer and the parallelism with a dial indicator (Niigata University practical training text)

  TolerancesPer machine, or the working accuracy tolerances of JIS B 6213

  Accuracy inspection standards include working accuracy tests (measuring test pieces actually cut) in addition to geometric accuracy tests (ISO 1986-1)

  ^[31][3]

• Measure roundnessCylinder

  ToolsRoundness measuring machine, coordinate measuring machine. If you have neither, use a micrometer, caliper, V-block and dial indicator

  ProcedureWithout a measuring machine, divide the difference between two diameters at the same cross-section by 2 (diameter method), or set the workpiece on V-blocks, rotate it, and read the difference between maximum and minimum runout (three-point method). If the shape is irregular, measure at more locations

  TolerancesDrawing specification

  The diameter and three-point methods give correct values only for workpieces whose shape can be assumed (JTEKT)

  ^[34](1 source, for reference)

• Check the operating condition before measuring accuracyCommon

  ToolsEyes and ears, touch (a vibration meter if needed)

  ProcedureCheck vibration, abnormal noise and stick-slip of components (running test), and rotation speed, feed rate and so on (performance test), before the accuracy inspection

  Tolerances— (accuracy inspection standards do not cover running tests)

  Grinding machine accuracy inspection standards (ISO 1986-1, ISO 3875, etc.) deal only with verifying accuracy, and treat the running test as something normally checked before accuracy is measured

  ^[3][14][2]

• Measure geometric accuracy and alignment in periodic inspectionCommon

  ToolsTest bar, granite surface plate (reference for parallelism), dial indicator / test indicator

  ProcedureAt UNITED GRINDING, an inspection starts with a visual check, then verifies geometric accuracy and alignment (example from the company's tool grinders: a test bar for runout and axis geometry, a granite surface plate for axis parallelism; remove the guide shoes to check condition, preload and play)

  TolerancesPer-machine inspection certificates and standard tolerances

  Okamoto provides on-site static accuracy inspection and machine correction as part of its after-sales service

  ^[22][23][24]

• Re-check the machine levelCommon

  ToolsPrecision level

  ProcedureIf form errors appear (roundness, cylindricity, taper), suspect the machine level along with spindle runout, support rigidity and chucking eccentricity

  TolerancesInstallation standard for each machine model

  JTEKT lists unstable centering and level adjustment during setup as one sign that aging is making accuracy unstable

  ^[25](1 source, for reference)

• Measure wheel runoutCommon

  ToolsDial indicator

  ProcedureRotate the wheel and measure the runout of its surface. If it runs out, true it so the periphery is concentric with the spindle

  TolerancesDepends on machine and application (no common figure was found in primary sources)

  UNITED GRINDING includes wheel runout, mounting and cutting ability in its inspection

  ^[26][27][28]

• Check dimensional change with temperatureCommon

  ToolsThermometer, measuring instruments

  ProcedureRecord how dimensions and form change between morning and evening and after continuous running. Also check the difference in size right after machining and after the part has cooled

  Tolerances—

  JTEKT divides heat into two kinds: thermal displacement of the machine (the wheelhead and bed move with temperature) and thermal expansion of the workpiece from grinding heat (it swells during machining and shrinks when stopped). UNITED GRINDING gives a difference between grinding fluid and room temperature of within ±1°C as ideal

  ^[25][32][33]

≡Related standards

• Flat surfaceJIS B 6213:2006 Test conditions for surface grinding machines with horizontal grinding wheel spindle and reciprocating table — Testing of the accuracy / ISO 1986-1:2001 (identical = IDT). On the ISO side, the 2014 edition (2nd edition) is currentCovers general-purpose machines of normal accuracy with a table length of 1600 mm or less. Specifies inspection methods and tolerances for static accuracy and machining accuracy (JIS preview)^[1][2][3]
• Flat surfaceJIS B 6251:2004 Test conditions for surface grinding machines with vertical grinding wheel spindle and reciprocating table — Testing of the accuracy / ISO 1985:1998 (modified = MOD). On the ISO side, the 2015 edition (4th edition) is current and covers manual and NC machines^[4][5]
• Flat surfaceJIS B 6214:1996 Test conditions for surface grinding machines with vertical grinding wheel spindle and rotary table — Testing of the accuracyThe corresponding international standard could not be confirmed from the JSA bibliographic record^[6](1 source, for reference)
• Flat surfaceISO 4703:2001 Accuracy tests for double-column surface grinding machines (slideway grinding machines) (ISO's listing marks it for review = 90.92)No corresponding JIS was found^[7](1 source, for reference)
• CylinderJIS B 6212:2006 Test conditions for external cylindrical and universal grinding machines with a movable table — Testing of accuracy / ISO 2433:1999 (IDT)Covers general-purpose cylindrical and universal grinders of normal accuracy with swing up to 800 mm and distance between centers up to 4000 mm. Covers static accuracy, machining accuracy and positioning accuracy (JIS preview)^[8][9][10]
• InternalJIS B 6211:2006 Test conditions for internal cylindrical grinding machines with horizontal spindle — Testing of accuracy / ISO 2407:1997 (IDT). A 2024 edition (4th edition) of the ISO standard has been issued; it includes geometric accuracy, positioning accuracy and machining accuracy^[11][12]
• CenterlessJIS B 6220:2021 Test conditions for external cylindrical centerless grinding machines — Testing of the accuracy / ISO 3875:2020 (IDT)Covers manual and NC external centerless grinders. Covers geometric accuracy, machining accuracy, and the accuracy and repeatability of positioning axes (ISO description)^[13][14]
• CommonJIS R 6243:2018 Grinding wheels — Static test and inspection methods for balance of grinding wheels / prepared by modifying ISO 6103:2014 (MOD)Standard for permissible unbalance of wheels as delivered and its test method (ISO 6103 covers general wheels with an outside diameter of 125 mm or more and a maximum operating speed of 16 m/s or more; diamond and CBN wheels and centerless regulating wheels are excluded). The draft was prepared by the Japan Grinding Wheel Industry Association^[15][16][17]
• CommonJIS R 6241:2018 Grinding wheels — Maximum operating speed, JIS R 6240:2018 Grinding wheels — Test methods, JIS R 6242:2023 Grinding wheels — Shapes, designation and marking (modified adoption of ISO 525:2020)Standards for the maximum operating speed, testing and marking of grinding wheels. Only the titles and the corresponding ISO standards were verified (the full text is paid)^{[18][19][20][21]}

The standard texts are paid, so tolerances are written from sources such as in-house standards published by machine manufacturers. For the correspondence between standards, see the standards correspondence table as well.