Steel, 1.7227 (42 CrMoS 4 V)

tempered to tensile strength

Rm = 1220 ... 1400 N/mm²

fine turned and slide ground

blackened BT

GEOMET 500-treated G0

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, which usually have a tapered transfer from shank to head (the so-called trumpet) to avoid fouling of the washer.

Chamfer edge F

The extended chamfer side F as seen from d₃ creates with d₁ an edge the so-called trumpet of the transfer from shank to head of the bolt, so that the smallest radial clearance prevails. Even with the smallest angle of 680 and the lower dimension of d₃ and d₁ the radial clearance of all bolts to DIN EN is still sufficient.

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.