hv bolts


The HV Bolts following EN 14399-4 and DIN 6914 is to use thinner nuts and shorter thread lengths to obtain the required ductility by plastic deformation of the threads within the nut. The HV bolt assembly is used in both preloaded and non-preloaded applications, and it can be argued that in the event of failure by thread plastic deformation the assembly still acts as a non-preloaded assembly. These assemblies are more sensitive to over-tightening during preloading and therefore require more site control. If severely over tightened during preloading the mode of failure by plastic deformation of the engaged thread of the bolt assembly offers little indication of impending failure.

These HV bolts are forged on heavy upsetting machines and are then machined on latest CNC machines in our factory, we also do the heat treatment in our factory using an advanced SQF sealed quench heat treatment furnace from DOWA Japan, the heat treatment furnace is SCADA controlled and provides 100% repeatability batch after batch. The heat treatment result is a perfect marten site after hardening and gives perfect results after tempering as per standard requirement.

Bolt Grades

We provide 8.8 & 10.9 grades bolts with assembly of nut and washer. The choice of the grade depends upon the application and requirement of the customer. The grades 8.8 or 10.9 have separate mechanical characteristics which are defined in ISO 898-1.

HV bolts characteristics:

  • Large under-head surface
  • Reduced setting
  • Large under-head radius
  • Improved fatigue strength
  • Enables preloading
  • RFL Mark


HDG, Zinc Plated, Zinc Flake, Black Oxide, Xylan, PTFE, Geomat, Chrome finish

We can offer surface finishing as per customer requirement in hot dip galvanising, we take special care to ensure there is no hydrogen embrittlement in 10.9 grade with our special curing system which ensures that 10.9 grade bolts are not damaged by hydrogen embrittlement post galvanizing process. We also do zinc electroplated in blue, yellow or black color as per customer requirements.

Special coatings in specific industries require zinc flake coatings, these coatings are done as per ISO 10683, depending upon customers requirement for salt spray life we offer coating systems from NOF Japan and Doerken from Germany, these coatings are provided with the help and support of our partners who have the required license and have successfully done validations with our existing customers. Salt spray life can vary from 500 to 1500 hours.