GN 6339 Heavy Duty Washers Steel, High Type

Outer diameter d₂
The outer diameter d₂ of the low type corresponds to DIN 125 / ISO 7089 washers. The high type corresponds to DIN 7349 washers.

Chamfer diameter d₃
Together with the chamfer angle α 70° and the inner diameter d₁ , this dimension is the most important one of these heavy duty washers. Even in the lower tolerance range, the diameter d₃ is generally larger than the maximum contact under head diameter on a bolt.
This will ensure that the chamfer of d₃ of the hardened washer will not be pressed into the under head radius causing an indentation which would damage the bolt.

Inner diameter d₁
The inner diameter d₁ is kept as small as possible ensuring that the bolt is guided centrically in the washer. The choice of a matching pair of bolt and washer with least radial clearance is important in order to avoid a mismatch between chamfer diameter d₃ and the maximum contact area diameter of the bolt head.

Chamfer angle α = 70° ± 2°
This relatively large angle is necessary when using hex headed bolts to avoid interference with the chamfer diameter d₃ of the washer.

Chamfer edge F
The extended chamfer edge F, as seen from d₃, and d₁ create an edge that provides the smallest radial clearance towards the transition from bolt shank to head. Even with the minimum chamfer angle of α = 68° and the smallest dimensions for d₁ and d₃, this radial clearance is sufficient for all bolts according to DIN EN.

Guide height h
This is the height of the cylindrical part of the inner diameter d₁. The dimension h should be as high as possible in relation to the thread pitch of the bolt.

Washer thickness s
GN 6339 heavy duty washers are higher than comparable DIN washers (exception: DIN 7439 which is equal to the high type).
A larger thickness leads to a stronger washer. In addition, taking the chamfer d₃ into consideration, a minimum guide height is provided which ensures that the thread will not be damaged when tightening.