Fit the guard and wear goggles plus a face shield before using an angle grinder; hold it with both hands, and never fit a woodworking saw blade to cut wood

Goggles and a face shield cost a few dozen yuan. Before each use, check the guard and disc; unplug before changing discs. This adds a minute or two. The hard part is keeping the guard on and using both hands even when it feels inconvenient.

The Canadian Centre for Occupational Health and Safety and safety authorities in Queensland, Australia, recommend the following. Check the guard and disc before starting; do not use a cracked, chipped, or distorted disc. The maximum speed marked on the disc must be at least the speed marked on the machine. The disc diameter and center hole must match the machine. Disconnect the power before changing discs. Secure the workpiece before grinding or cutting. Wear safety glasses or goggles with a face shield over them. Hold both handles with both hands and stand firmly. Never use a cutting disc for grinding, which makes it more likely to break. Do not put the machine down until the disc has stopped completely. Direct sparks and debris away from people, and keep flammable materials away. A Queensland safety notice says cutting discs are designed for an edge speed of about 70 meters per second. Fitting a 356 mm disc to a 230 mm machine raises the edge speed to at least 120 meters per second and can shatter the disc. In February 2016, a local worker using a 230 mm angle grinder was hit in the chest by a fragment and died from internal injuries. China has two accident investigation reports. In Harbin in 2019, a worker replaced a cutting disc with a toothed saw blade and cut wooden boards without a guard. The blade caught his trousers, severed a thigh artery, and he bled to death. In Shenzhen’s Futian District in 2024, a worker cut a wooden door frame with an angle grinder fitted with a woodworking saw blade but no guard or auxiliary handle. The machine kicked back, severed a carotid artery, and he died. The national standard cited in the report says not to attach a saw chain, woodcarving blade, or toothed saw blade. South Korean emergency injury surveillance from 2011 to 2018 recorded 8697 injuries from high-speed rotating cutting tools, including 4603 while using tools in the grinder category. Of those injuries, 46.4% involved the hands and 23.0% the head. Compared with other tools in the same broad category, grinders were associated with roughly twice the odds of severe injury (OR 2.07, 95% CI 1.88–2.29). A hospital in Mianyang, Sichuan, admitted 36 patients with angle-grinder eye injuries over two years. After surgery, 10 still had best corrected visual acuity below 0.05. Of 742 acute hand and forearm injuries treated at a Turkish hospital over one year, 82 were caused by angle grinders. All but 8 occurred outside work, and 44% of patients were retired. Among 15 patients injured by angle grinders at a Japanese trauma center in 2017 to 2018, 9 had misused them, such as fitting saw blades to cut wood. Two lost an entire finger and one lost part of a finger (Canada, Australia / China / South Korea, Turkey, Japan).

Canadian Centre for Occupational Health and Safety (2025). Abrasive Wheels - Use of Portable Grinders. https://www.ccohs.ca/oshanswers/safety_haz/abrasive_wheels/safeuse1.html；Canadian Centre for Occupational Health and Safety (2025). Powered Hand Tools - Use of Grinder Attachments. https://www.ccohs.ca/oshanswers/safety_haz/power_tools/powered-hand-tools-use-of-grinder-attachments.html；Workplace Health and Safety Queensland (2017). Guards and discs on angle grinders. https://www.worksafe.qld.gov.au/news-and-events/alerts/workplace-health-and-safety-alerts/2017/guards-and-discs-on-angle-grinders；哈尔滨市松北区人民政府 (2019). 哈尔滨三发装卸运输有限公司「8.28」机械伤害事故调查报告. https://www.songbei.gov.cn/hebsbq/tzgg/201910/c01_797872.shtml；福田区人民政府沙头新洲南村房屋装修工程「3·14」一般机械伤害事故调查组 (2024). 沙头新洲南村房屋装修工程「3·14」一般机械伤害事故调查报告（引 GB 3883.3-2007 第 8.12.1.102 条 a、e 项）. https://www.szft.gov.cn/attachment/1/1507/1507749/11317197.pdf；Song J, Jeon YB, Jang JH, Cho JS, Choi JY, Choi WS. (2023). Severity of grinder injuries and related factors compared with other high-rotation cutting tool injuries: a multicenter retrospective study from 2011 to 2018. Journal of Trauma and Injury, 36(1), 32-38. https://doi.org/10.20408/jti.2021.0057；Ke W, Gu K, Zhu S, Wu J, Dai Y. (2025). Prognostics Factors to Avoid Eye Injuries in Angle Grinders. Journal of Craniofacial Surgery, 36(6), e629-e631. https://doi.org/10.1097/scs.0000000000011108；Sozbilen MC, Dastan AE, Gunay H, Kucuk L. (2018). A prospective study of angle grinder injuries in the hands and forearms during a one-year period. Hand Surgery and Rehabilitation, 37(5), 300-304. https://doi.org/10.1016/j.hansur.2018.07.002；Tsumura T, Matsumoto T, Matsushita M, Kishimoto K, Shiode H. (2021). Do Not Cut Wood with an Angle Grinder, or You Might Lose a Finger: A Retrospective Study. Journal of Hand Surgery Asian-Pacific Volume. https://doi.org/10.1142/s2424835521500053

Rated C because these practices come from safety-agency guidance and accident investigations; no study has calculated how many injuries following them prevents. The injury data show severity only and all come from a single hospital or country. Benefit magnitude is rated medium as a judgment: consequences can include death, blindness, and finger amputation, but apply only to people using angle grinders. The Harbin machine’s manual already prohibited toothed saw blades and required a guard. That worker had a handsaw nearby; wood should be cut with it or a similar woodworking tool. Secure loose clothing, hanging jewelry, and long hair, which can be caught in the machine. Grinding creates substantial dust and noise; for masks and earplugs, see Section 19, Item 10 (the employer must provide protective equipment). If a major blood vessel is cut, press firmly and continuously on the wound; see Section 13, Item 12 (press hard on the wound first for major bleeding). The main beneficiary is you, and this also protects family members helping nearby.