Safety in grinding machine maintenance work

⚠What laws and standards require

• Article 117 of the Industrial Safety and Health Regulations (Japan) (guards for grinding wheels)

  Provide a guard when a rotating grinding wheel could be hazardous. Wheels under 50 mm in diameter are excluded

  The Structural Standard for Grinding Machines (Japan) also requires grinders (except internal grinders) to have a guard that conforms to the standard. OSHA likewise says wheels may be used only on machines with guards, except for wheels used inside a workpiece, such as internal grinding wheels^[1][2][3]

• Article 118 of the Regulations (trial run of grinding wheels)

  Run the wheel for at least 1 minute before starting the day's work, and for at least 3 minutes after changing a wheel

  There is a fatal accident in which an old wheel 65 cm in diameter burst at a workplace that was not doing trial runs (MHLW). Noritake cautions not to stand in front of the wheel in its direction of rotation during the trial run^[1][4][5]

• Article 119 of the Regulations (prohibition of use above the maximum operating speed of grinding wheels)

  A grinding wheel must not be used above its maximum operating speed

  Before mounting a wheel, confirm that the wheel spindle speed does not exceed the maximum operating speed marked on the wheel (OSHA says the same). There is a surface grinder burst case where a wheel of 405 mm outside diameter and 1800 m/min maximum operating speed was run at 1450 min⁻¹ (MHLW)^[1][4][3][6]

• Article 120 of the Regulations (prohibition of side use of grinding wheels)

  Do not use the side of a wheel unless it is a wheel designed for side use

  There is a case where a straight wheel burst after its side was used (MHLW; overspeed, a wheel and guard not suited to the machine, and a lack of special training were also involved)^[1][4][7]

• Article 36 item 1 of the Regulations / Article 1 of the Special Training Rules for Safety and Health (work of changing grinding wheels, etc.)

  Special training must be given before assigning work on changing grinding wheels and test-running them after the change. For wheels for machine grinding: classroom (knowledge of grinders, wheels and mounting fixtures, 4 hours; mounting method and trial run method, 2 hours; related laws, 1 hour) and practical training (mounting method and trial run method, 3 hours or more)

  The classroom subjects include visual and ring-test inspection of wheels, the tightening method and tightening force of mounting fixtures, balancing, and the trial run method. Special training records are kept for 3 years (Article 38 of the Regulations). Wheels for free grinding (bench grinders, etc.) are covered by a separate training under Article 2^[1][8][4]

• Article 42 of the Industrial Safety and Health Act / Article 13 paragraph 3 item 2 of its Enforcement Order / Article 27 of the Regulations (machinery and equipment that must meet standards)

  Under Article 13(3)(2) of the Enforcement Order, grinding machines, grinding wheels and wheel guards are subject to Article 42 of the Industrial Safety and Health Act. Under Article 27 of the Regulations, they may not be used unless they meet the standard set by the Minister of Health, Labour and Welfare (Structural Standard for Grinding Machines, etc.)

  JIS B 6033 (safety of grinding machines) is based on ISO 16089, but states that in Japan the structural standard, which has the force of law, must take priority when applying it^{[9][1][2][10]}

• Main requirements of the Structural Standard for Grinding Machines, etc. (Ministry of Labour Notification No. 8 of 1971)

  Flanges (material, same diameter on both sides, straight flanges at least 1/3 of the wheel diameter), guards (material, thickness, extent of wheel coverage, no holes that weaken them), power cut-off device (operable from the working position), markings (grinder, wheel, guard), work rest for bench and floor grinders (gap to the wheel of 3 mm or less) and adjusting tongue (gap to the guard of 10 mm or less), a fixed-side flange that is fixed in place, and a wheel spindle tightening screw that tightens in the direction of rotation

  OSHA 1910.215 also has provisions with the same intent: flanges (at least 1/3 of the wheel diameter), labels, a ring test before mounting, work rest (within 1/8 inch), tongue guard (within 1/4 inch), and so on^[2][3][4]

• Ordinance on Industrial Safety and Health (Japan), Articles 28 and 29 (Keeping safety devices effective)

  The employer keeps guards and safety devices inspected and maintained so they stay effective. Workers must not remove guards or safety devices or make them ineffective. When temporarily removing one, get permission and put it back immediately afterward

  There is a case where work continued with the guard open to check the contact during dressing, and fragments of a burst wheel hit the worker. As a countermeasure, MHLW says it is desirable to build in an interlock that allows the guard to be opened only in a low-speed check mode^[1][10][11]

• Ordinance on Industrial Safety and Health (Japan), Articles 107 and 108 (Stopping operation when cleaning, and when cleaning the cutting part)

  For cleaning, lubricating, inspecting, repairing or adjusting a machine, and for cleaning, inspecting, repairing, replacing or adjusting the cutting part (the wheel on a grinder), stop the machine when there is danger, and lock the starting device or attach a sign so no one else can start it

  Changing the wheel, cleaning the chuck surface, cleaning the grinding fluid tank and filtration unit, and servicing hydraulic and hydrostatic parts are done only after stopping and applying lock and tag (lockout/tagout). Release the pressure in hydraulic circuits that hold residual pressure^{[1][12][13][14]}

• Ordinance on Prevention of Dust Hazards (Japan) (Appended Table 1 item 7, Appended Table 2 item 7, Articles 3, 4 and 17)

  Work that grinds metal with abrasives under power is dust work. A place where metal is ground indoors with a machine that has a rotating body, such as a grinder, is a designated dust source and requires local exhaust ventilation or equipment that keeps the work wet. Work that grinds while water or oil is supplied by equipment is exempt from the provisions of Chapters 2 to 6

  When grinding without water or oil supply equipment (dry), local exhaust ventilation and similar measures are required, plus an annual voluntary inspection of that equipment (records kept for 3 years). Noritake also recommends preventing dust dispersal and providing good ventilation^[15][4]

• JIS B 6033:2018 Machine tools — Safety — Stationary grinding machines (modified adoption of ISO 16089:2015)

  Requirements to eliminate hazards and reduce risk on stationary grinding machines that mainly grind metal. Divided into manual machines (Group 1), manual machines with power-driven axes (Group 2) and numerically controlled machines (Group 3)

  It is built on the idea of anticipating that interlocks will be disabled so operators can see better, and providing a special operating mode with safety measures comparable to setup. ISO 16089 has a 2025 edition (2nd edition)^[16][10][17]

• US 29 CFR 1910.215 (machinery using abrasive wheels)

  Upper limits of guard exposure angle (cylindrical grinders 180°, surface grinders using the wheel periphery 150°, bench and floor grinders 90°), flanges, labels, inspection and ring test before mounting, fit between the hole and the wheel spindle, and no foreign matter on contact surfaces

  The Japanese structural standard shows exposure angles and so on in figures. Useful as a reference for comparison^[3](1 source, for reference)

• MHLW accident case 101102 (burst during dressing on a CNC cylindrical grinder)

  After a 5-minute trial run with a new wheel, the wheel burst during dressing. The guard was open, so the fragments scattered. There was a metal particle between the flange and the wheel, and a hex wrench and hammer were used for tightening instead of a torque wrench

  Even if the trial run shows nothing wrong, poor assembly can lead to a burst later. Always check for foreign matter, tighten evenly with a torque wrench, and dress with the guard closed^[11](1 source, for reference)

• MHLW accident case 101224 (wheel burst on a surface grinder)

  Of the stands lined up and fixed with magnets, the two at the end shifted and lifted, applying excessive local force to the wheel, which burst. The magnet switch of the stand had loosened and turned OFF. The wheel was being run above its maximum operating speed

  The countermeasures listed are checking that the workpiece is secured before grinding, calculating and verifying the peripheral speed, and safety and health education for workers^[6](1 source, for reference)

• Protective equipment and countermeasures against sparks and flying objects

  Wear protective equipment such as safety glasses and a dust mask during work. Block flying sparks with shields. Do not enter the range of the sparks. Do not touch the rotating wheel directly. Do not force the workpiece against the wheel

  Article 105 of the Regulations requires guards or enclosures on machines where workpieces and the like may fly off, and requires protective equipment to be used where that is difficult^[4][1]

• Fire countermeasures for oil-based grinding fluid (maker's cautions)

  Machines that use oil-based grinding fluid need fire-extinguishing equipment (automatic fire suppression) and an oil cooling unit. Use grinding oil with a high flash point

  UNITED GRINDING writes that when installing a new machine, you should verify the connection and start-up of the fire suppression system and provide extinguishers that comply with local regulations^[18][19](1 source, for reference)

• Work rest and adjusting tongue of bench and floor grinders (Structural Standard for Grinding Machines, etc., Articles 5 and 28)

  The work rest must be adjustable to a gap of 3 mm or less from the wheel periphery. The guard must be adjustable with an adjusting tongue or the like so that the gap between the wheel periphery and the guard at the part needed for grinding is 10 mm or less

  These are rules for double-end grinders and the like used in the same shops as surface and cylindrical grinders. There is a fatal accident where a fragment of a broken wheel hit the chest on a floor grinder used without an adjusting tongue (MHLW). Noritake recommends a work rest gap of 3 mm or less and a gap to the tongue of 3–10 mm^{[2][4][3][20]}

The legal provisions are summarized in Kezuriba's own words. Check the exact wording against the original text in e-Gov Law Search.