Approximate determination of surface pressure

underneath the bolt head or nut contact area.

Conditions:



F_M - Mounting prestressing force for selected bolt [N]
A_p - Contact area under bolt head or nut [mm²]
p_G - Limiting surface pressure [N/mm²] for the pressed parts

With hexagon head bolts, the reduced contact area due to hole chamfer and seating plate must be taken into consideration.



for d_h > d_a

d_h - Bore diameter
d_a - I.D. of head contact area
d_w - O.D. of head contact area

Table 3: p_G - Limiting surface pressure [N/mm²]
for the pressed parts

Material	pG Limiting surface pressure
St 37	260 N/mm²
St 50, C 45 N, 46 Cr 2 N, 46 Cr 4 N	420 N/mm²
C 45, profile rolled (KD 210)	700 N/mm²
C 45 V, 46 Cr 4 V, 42 CrMo 4 V	700 N/mm²
GG 25	800 N/mm²

If these surface pressures are exceeded, washers of respective sizes and strengths must be provided.

• Calculation module

• Top