Arbor Thread
Affiliate link — we may earn a commissionThe arbor thread is the threaded spindle on the grinder where the wheel mounts. Most 4-1/2 and 5-inch angle grinders use a 5/8-11 UNC thread (5/8-inch diameter, 11 threads per inch). European and some Asian grinders use M14 x 2.0 metric threads instead. The thread size is stamped on the spindle or listed in the manual. Every wheel, flap disc, wire cup, and adapter you buy has to match the arbor thread. Wrong thread means the wheel doesn't mount. There are no adapters for mismatched arbor threads on grinders.
Why It Matters
There are only two common sizes (5/8-11 and M14), but if you buy the wrong one, the wheel literally can't go on the tool. Check your grinder's arbor thread before ordering accessories. Most US-market grinders are 5/8-11.