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Explanations

Clamping screws:Setting an axial pretension force:

Cheese-head screws with a hexagon socket in compliance with ISO 4762 strength class 12.9. µ= 0.14. As the effective friction coefficientsdepend on a range of factors which are often beyond the control of the manufacturer, values specified here are without com- mitment and are made in the form of recommendations. M
A : Tightening torque per clampingscrew. The tightening torque is based on a friction coefficient The axial pretension of a screw con-nection often plays a decisive role for successful function, and must there- fore be set with particular accuracy. However, in most assembly works- hops, direct measurement of this vari- able is not possible, raising the need for indirect methods of setting. For this purpose the locknut pretension moment is calculated corresponding to the required pretension force. This factor can be determined using the following formula: The locking process strains the spindle thread with the effect of an intensive surface contact (= high axial rigidity). At the same time, this serves to relieve tension on the end contact surface of the locknut. This effect can be simply compensated by set- ting an increased pretension torque during mounting. This higher preten- sion torque is ascertained using the allowance B relative to the required pretension force Fv.Mv = (Fv + B)· (A + µ
A · r
A )[Nm] Mv=Pretension momentof the locknut [Nm]Fv= Required axial pretension forceof the screw connection [N] B=Locknut-specific allowance [N],compensates face end relief due to the locking process A=Constant [mm], includes thecalculation factors for the respective thread diameter (see table) µ 1000
A =Friction of coefficient for theend contact surface of the locknut. Approximate value µA = 0,1 steel/stellr
A =Effective friction radius for the end contact surface of the locknut [mm]

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