A through-hardened (thru-hardened) washer is a standard flat washer that is specially hardened for use with Grade 5, Grade 8, and A193-B7 bolts.  It helps increase the bearing surface of the bolt by spreading the force out radially. These products only come in one grade and are either plain or zinc/yellow. You may also consider looking at F436 structural washers (designed for A325 and A490 bolts).

Talk to Hardware Everywhere’s knowledgeable customer service team for help choosing the fasteners that match your application. Call us at 1-800-432-8979 or contact us online.