Genuine MTD 712-0117 — center hex lock nut (superseded by part 912-0117).

A sturdy hex “center” nut used to secure spindle / deck center-lock fittings on mower decks — a direct-fit nut referenced in MTD deck assembly diagrams (for example on models such as 146S845H088 / TMO-3399006 (1996) and similar 46" deck assemblies). MTD parts like this are often shown in the parts diagram as CC712-0117 (use 912-0117).

Shown in MTD catalogs and parts lookups as Nut‑Hex Center (L‑1) and commonly cross-referenced under 912-0117 across MTD parts listings and reseller catalogs — this is the original MTD center nut you need to resecure spindle/center-lock components.

(If your parts diagram shows 712‑0117 or 912‑0117 at a spindle or deck center, this nut is the intended replacement.)