Flange Nut
Affiliate link — we may earn a commissionThe flange nut is the fastener that locks the wheel onto the grinder's spindle. A standard angle grinder has an inner flange (fixed to the spindle) and an outer flange nut that you tighten with a spanner wrench. Many modern grinders include a tool-free nut that you can tighten and loosen by hand. The flange nut must be fully seated and tight before you run the grinder. A loose nut lets the wheel wobble, which can crack the disc and send fragments into your face. Always check the nut before starting.
Why It Matters
A grinding wheel spinning at 11,000 RPM with a loose flange nut is a fragmentation hazard. Tighten it until it's snug, but don't over-torque it or you'll struggle to remove it later. Tool-free nuts are worth the $10 premium if you change wheels often.