Power tools
How to choose an angle grinder — and use it without losing an eye
Buy a 4.5-inch (115mm) angle grinder first — it costs KES 3,500–12,000 in Kenya and handles most cutting and grinding. Add a 9-inch only if you cut heavy section. Never run one without its guard, always check the disc's rated speed against the tool, and wear a face shield rather than goggles.
7 min read · updated 19 July 2026
The angle grinder is the most-used power tool on a Kenyan site and the one that causes the most serious injuries. Both facts come from the same source: it is cheap, it does everything, and it is treated casually.
Size sets the job
| Disc size | Typical power | Cuts to | Use it for |
|---|---|---|---|
| 115 mm (4.5") | 650–950 W | ~25 mm steel | General cutting, grinding welds, tile, rebar |
| 180 mm (7") | 1,500–2,000 W | ~55 mm steel | Heavier fabrication, concrete with diamond blade |
| 230 mm (9") | 2,000–2,600 W | ~70 mm steel | Structural section, stock removal, demolition |
Start with 115mm. It is light enough to control one-handed, and a machine you can control is a machine that does not injure you.
Corded or cordless
Corded, in almost every case. Grinding draws heavy sustained current and a cordless grinder empties a 5.0Ah battery in minutes. Buy cordless only if you regularly work where there is no power — and then buy the largest batteries the platform offers.
The four rules that prevent the injuries
- The guard stays on. Always, however inconvenient. It is the only thing between a bursting disc and your face.
- Check the disc's rated speed. It must be equal to or higher than the grinder's no-load RPM, printed on both. A disc rated below the tool will come apart at speed.
- Cutting discs cut, grinding discs grind. A 1mm cutting disc is designed for edge loading only. Lay it flat to grind and it will shatter.
- Face shield, not goggles. Grinder eye injuries are the most common serious workshop injury in this trade, and sparks find their way around goggles.
What separates a good grinder from a cheap one
Not the wattage. Cheap machines quote generous wattage figures and fail for a different reason: metal dust gets into the motor. The machines that last have sealed or coated windings and labyrinth bearing protection. Makita's zig-zag varnish is the well-known example.
The other feature worth paying for is an electronic brake, which stops the disc within three seconds of releasing the switch. Without one the disc spins for 15–20 seconds after you set the tool down, and that is when it walks off a bench or a hand goes near a wheel that looks stationary.
Discs are where the money actually goes
A grinder is a one-off purchase; discs are forever. Buy 1mm cutting discs for sheet and bar, 6mm grinding discs for welds, flap discs for finishing, and a diamond blade for tile and block. Buying good discs improves the cut far more than spending more on the tool.
Common questions
What size angle grinder should I buy?
4.5-inch (115mm) for general work — it is light, one-handed and cuts steel up to about 25mm. 7-inch and 9-inch machines cut deeper and grind faster but are heavy, two-handed and considerably more dangerous. Most fabricators own both.
Can I put a bigger disc on a small grinder?
No. The guard is sized for the rated disc, and an oversized disc extends past it. It also exceeds its safe rim speed on a faster machine, which is how discs burst. Fit only the size the grinder is rated for.
How long do cutting discs last?
Resin-bonded discs carry an expiry date, typically three years from manufacture, because the bond degrades over time. Discard any disc past its date, any disc that has been dropped, and any disc with a visible chip.