for steel construction


The HEICO-LOCK® HLK-washers deliver high quality anti-vibration security for HV sets according to DIN EN 14399-4 and DIN EN 14399-8.

Even under extremes of vibration or severe dynamic loads in steel construction the HEICO-LOCK® HLK-washers, which are approved by the German Institute for Structural Engineering (DIBt), provide maximum reliability. Due to the increased under head radius of HV bolts, the HEICO-LOCK® HLK-washers are chamfered on the internal diameter to ensure optimal surface contact while tightening.



  • Designed to secure HV sets according to DIN EN 14399-4 and DIN EN 14399-8
  • Replacing washers according to DIN EN 14399-6
  • Approved and certified construction product (certificate of conformity)
  • Approved for use by General Building Supervisory Authority (DIBt) Approval No Z-14.4-702
  • Very easy to install and remove (HLK-washers are supplied as a pre-assembled pair)
  • The double chamfer also ensures that the HEICO-LOCK® HLK-washers cannot be applied incorrectly, so avoiding operator error
  • High corrosion resistance provided by use of a zinc-flake coating
  • Available for HV sets from M12 up to M36




An important feature of the HEICO-LOCK® HLK-washers, setting them apart from commonly used plain, chamfered washers (according to DIN EN 14399-6), is the prevention of self-loosening through the certified HEICO-LOCK® wedge locking principle.


  • Wedge-shaped surface on the inside of the HLK-washers, radial teeth on the outside
  • Interlocking embedding of the radial teeth with the respective mating surface (when the bolted connection is tightened)
  • System movement only possible between the inside washer surfaces, allowing the securing system to readjust itself automatically
  • Increase in clamping force


Technical Data


1. Difference in hardness: HHEICO > HMaterial

  • The surface hardness of HEICO-LOCK® HLK-washers is greater than the hardness of HV sets according to DIN EN 14399-4 and DIN EN 14399-8 (grade 10.9; max. 380 HV)
    • HLK-washers: Steel (through-hardened; 485 ± 25 HV0.3)

2. Difference in angles: α > β

  • The wedge angle (α) of the HEICO-LOCK® HLK-washers is greater than the pitch (β) of the bolt thread
  • This angle means the expansion in thickness of the HEICO-LOCK® HLK-washers is greater than the possible longitudinal movement of the bolt along the thread

3. Difference in friction: μa > μi

  • The wedge-shaped surfaces have a considerably lower friction coefficient (μi) than the toothed outside of the washers (friction coefficient μa)
  • Loosening caused by dynamic stresses causes movement between the two HLK-washers in the region of the wedged surfaces

4. Difference in preload: Fdyn > Fstat

  • An expansion in thickness of the HEICO-LOCK® HLK-washers as a result of loosening leads to an increase in the clamping force
  • This causes an increase in the preload compared to when in a static state and thus causes the bolt to self-lock

5. Dimensions of HEICO-LOCK® HLK-washers

  • With both parts of the washer having a chamfer on the internal diameter, the HLK-washers are specifically designed to compliment the increased radius between the underside of the bolt head and the bolt shank of HV bolts, thus ensuring there is no interference with the underhead radius of the bolt and a secure bolted joint is maintained


Installation information

HV sets need to be secured on both
sides of a through-hole: One pair
of HLK-washers under the bolt head
and one pair under the nut body.
HEICO-LOCK® HLK-washers are a
direct substitute for the commonly
used plain chamfered washers,
according to DIN EN 14399-6, so no
locking function is achieved when
combining the HLK-washers with
additional washers or fasteners.


Fields of application




Product overview

Item No
Box Qty
M12 HLK-12 13 24 200
M16 HLK-16 17 30 100
M20 HLK-20 21 37 100
M22 HLK-22 23 39 50
M24 HLK-24 25 44 50
M27 HLK-27 28 50 25
M30 HLK-30 31 56 25
M36 HLK-36 37 66 25


For detailed information regarding the General Building Supervisory (DIBt) Approval No. Z-14.4-702 visit
www.heico-lock.com or www.dibt.de.