GN 6339

Heavy duty washers

The influence of a washer on the quality of the screwed connection is very often underestimated. With washers GN 6339, high quality preloaded screwed connections can be established.

A high static clamping force can be reached avoiding loss of tension.

At a specified preloaded clamping force it is often possible to use thinner bolts. This can result in a better ratio between clamping distance and bolt diameter to minimise the danger of failure.

The case hardened smooth bolt head/screw contact face leads to a lower and more constant friction co-efficient even when continuous clamping and releasing operations are required.

Washers GN 6339 are only suitable for machine construction bolts of classes 8.8 / 10.9 / 12.9, and not for steel bolts DIN 6914.

• ISO-Fundamental Tolerances -

 

Outside diameter d₂

The outside diameter d₂ of the lower type refers to washers DIN 125 / ISO 7089, and the higher type to washers DIN 7349.

Chamfer face diameter d₃

This dimension is, together with the chamfer angle α 70° and the inside diameter d₁, the most important dimension of these heavy duty washers. Diameter d₃ is actually, even in the lower tolerance range, larger than the max. 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 underhead radius causing an indentation on the bolt which would damage the bolt.

Inside diameter d₁

The inside diameter d₁ is kept as small as possible ensuring that the bolt is inserted centrically into 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 max. contact area diameter of the bolt head.

Chamfer angle α = 70° ± 2°

This relatively large angle is necessary when using hexagon headed bolts to avoid interference with the chamfer face 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.

Lead height h

This is the height of the cylindrical part of the internal diameter d₁, h should be as high as possible in relation to the pitch of the thread of the bolt.

Washer thickness s

Washers GN 6339 are higher when compared with DIN washers (exception: DIN 7439 which is equal to the high type).A larger thickness leads to a stronger washer. As a result, bearing in mind the chamfer d₃, a minimum height is established which ensures that the bolt thread will not be damaged when the bolt is tightened.