Metal cutting

• Angle-grinder cut-off disc

  125mm × 1.0–1.6mm for steel, separate iron-free for stainless; disc RPM rating ≥ grinder RPM.

• Cutting speed

  Steel 80–100 m/s by disc; recip saw — 14–24 TPI metal blades; bimetal for thick stock.

• Shears

  Sheet metal up to 1.5–2mm — electric shears are cleaner than a grinder, no sparks or edge hardening.

• Plasma/gas

  Plasma cutter — cleanest for 3–20mm; oxy-fuel — for thick stock but with scale and hardening.

The main grinder rule: a disc only for its material, disc RPM ≥ tool RPM. Grinder sparks are the #1 workshop fire cause: keep a clean 5m zone around.