Original MTD part 712-0392 — Hex lock (stop) nut, a direct replacement fastener used on belt/cover and idler assemblies of smaller MTD machines.

Features: plated steel hex lock nut with a 1/4‑28 UNF thread (approximately 6.35 mm diameter, thread pitch ≈0.91 mm) designed to resist backing off under vibration — the same style shown in MTD parts diagrams for tillers and small mowers.

Fits examples: commonly used on MTD rear- and front‑tine tillers and compact walk‑behind machines — e.g., model numbers 216‑420‑000, 216‑410‑000, 21AA412A000, 21A‑332C765, 300 and 330 (check your model diagram to confirm exact placement).

Why this one: if a threaded fastener at an idler, belt cover or tine assembly has failed or worked loose, the original MTD 712‑0392 lock nut restores the correct fit and vibration resistance so the machine operates safely. This is a genuine MTD replacement you can drop into the repair and get the unit back to service quickly — a smart choice when looking for reliable power tool parts.