Made to Order / All-Metal (Metric) Aztech Locknut Company > Core Products > Made To Order > All-Metal (Metric) Cone DIN 980V Mating part must extend at least one full thread past the nut surface to assure locking element engagement. Jam Hex Center Lock ISO 4035, ISO 8675 Jam Hex Center locknuts are selected when the application demands a very low profile and can accept the low proof load of the thinner jam nut. Jam Hex Top Lock ISO 4035, ISO 8675 Jam Hex Top locknuts are selected when the application demands a very low profile and can accept the low proof load of the thinner jam nut.