Grade 8 washer (special ID) and grade 8 special flange locknut (smooth underside; no serrations) for closing arm pivot point, JD 50/60/90 drill. Corresponding OEM parts are only grade 5, and wear out fairly quickly, which creates side-play and lets the spring for the closing arm pop out of its setting too easily.
LEGACY P/N WAS ARI 006 – Flange Locknut + Special Washer, for closing pivot point, JD 50/60/90 drills (Grade 8)