Hard Lock Nut – Precautions

Features of the Hard Lock Nut

  • When reusing a nut
    When reusing a Hard Lock Nut or Bolt, first fasten the first (convex) nut followed by manually screwing on the second (concave) nut until the two come into contact. A slight gap should remain. If there is a gap of about 1 pitch, the nut/bolt can be reused. If there is a gap of much less than one pitch or there is no gap, do not reuse .
  • When fastening with zero or extremely low torque (stress)
    Fix the first (convex) nut with a wrench, then fasten the second (concave) nut using the torque specified by Hard Lock. Note that if the first (convex) nut is not fixed, it may rotate with the second (concave) nut.
  • If the second (concave) nut is tight on the first (convex) nut with a fastening torque lower than the specification torque
    The Hard Lock Nut and HLB are produced with the tolerance set to JIS 2 grade (ISO 6H). In the event that the product (JIS 3 grade or ISO 8g) has a bolt or shaft lower than the JIS 2 grade or ISO 6g minimum value, the tolerance between the bolt and nut will be greater, such that it will be possible to fasten the second (concave) nut with a torque less than the Hard Lock standard value. We request that you replace that bolt or shaft with a JIS 2 grade or ISO 6g product as the looseness effect will be inadequate. If replacement is not possible (such as because a special product is being used), please contact us.
  • Hot-dip galvanizing
    Because of the thick galvanizing layer that results from hot-dip galvanizing, overtapped Hard Lock Nuts are used. Such products may not fit well with products having a thin coating such as produced by electrogalvanizing. Please confirm that nuts and bolts have the same surface treatment before use.
  • If Hard Lock’s product does not fasten to your bolts or shafts
    The Hard Lock control system the old JIS grade 2 (ISO 6H) for the screw grade of its nuts and HLBs. If the bolts and shafts you use also conform to the old JIS 2 grade (ISO 6g), they will fit without any trouble, but if the bolts and shafts are produced to fit to general nuts, some may not fit to specification. If there is a fitting problem with our products, we ask that you use an instrument such as a ring gauge to determine whether there is a specification problem.