In tapered roller bearings, run-out accuracy, a high level of axial rigidity and dynamic safety create a major contribution to perfect bearing operation: Radial stress applied to the tapered roller bearing generates axial forces (axial rigidity). Due to a lack of axial pretension (no axial friction), the intrinsic safety of the locknut is extremely important.
The use of a locknut gives the bearing of the ball roller spindle a high degree of axial rigidity. Under highly dynamic operating conditions, the high degree of dynamic safety of the locknut represents a major advantage.
A locknut is used here to provide precise and infinitely variable adjustment of the pretension of the spring on a friction clutch. The reliable locking function is of particular importance here.
The locknut ensures a high level of axial rigidity and excellent concentricity on the main spindle bearing in a turning lathe.
Not a millimetre is lost in the axial direction and, despite this, there is no need to sacrifice run-out accuracy, axial rigidity or a high degree of dynamic safety.
Due to the flat design, countersunk installation is possible without causing any interfering contours in the table surface. Straining of the structure due to a tilting locknut caused by thread flank play, or even opening under dynamic load are not possible due to the characteristic properties of the locknut.
The low installation height of the MSF locknut makes it possible to create a compact drive side of the spindle. This configuration saves valuable installation space and minimises destructive rotating bending stress. At the same time, the benefits of a Spieth high-precision locknut are fully exploited.
The installation using a locknut reliably transmits the high load-bearing capacity and axial rigidity of the needle axial cylindrical bearing to the feed drive system. The excellent locking properties provided by the locknut are of major importance under dynamic stress.
Competitiveness through technological leadership – a strategy that calls for an economical increase in power density, efficiency and accuracy. Locknuts create the foundation for this.
Lower resource input
- No additional grooves or locking plates required.
- Free, infinitely variable and exact positioning.
- Fast, precise installation results.
- Simple to dismantle thanks to back-sprung diaphragm.
- Optimum locking effect.
- High degree of run-out accuracy, even in the assembled state.
- High dynamic loading capacity.
- High dynamic rigidity.
- Dynamically balanced structure.
- Suitable for high speeds.
4 unique features – numerous benefits
The locking system enables the application of high clamping forces to ensure that the nut is friction-locked onto the spindle thread. The load is applied to the thread across 360° symmetrically and evenly. The locking force and working load act in the same direction and cannot cancel each other out. This is the requirement for the highest locking effect while at the same time preserving the connecting components.
The locking procedure is designed to exert a self-centring effect for the nut on the spindle thread. This is the prerequisite for ensuring a coaxial end position of the nut relative to the spindle and for a vertical orientation of the end face with respect to the connection assembly. For demanding applications, this effect can be used in a separate installation step specifically to minimise thread join play.
All functional surfaces that determine precision are manufactured in a single set-up. And in contrast to other locking concepts, the precision is retained by design once it has been created, even during installation and operation.
- Consistent rigidity
Irrespective of the degree of pretension in the nut, the closed distribution of locking force ensures an intensive application of the thread flanks in the direction of the working load. The assembly process creates an elastic pretension in the join of the thread pairing, as a result of which the bearing area of the thread flanks and the rigidity of the join are significantly increased. Damaging micro-movements, caused by strong impulses or abrupt changes in the direction of force, are drastically reduced.
In this example, based on a type MSF locknut. The principle is illustrated in a simplified diagram with enlarged thread flank play.
As with every threaded connection, there is a degree of mating play when the nuts are screwed on. As a result, the nut may be aligned with a parallel and/or angled axial offset relative to the spindle axis; in other words, the contact surface of the nut may be at an incline.
Unique: Spieth locknuts are automatically self-centring and eliminate mating play (thread flank play) as far as possible. Thanks to play restriction, the locknut centres itself and the contact surface of the engages at right angles to the spindle axis.
The locknut is tightened with the required level of preliminary torque. The lock screws are then locked with the specified level of locking torque. This ensures optimum contact at the thread flanks and maximum concentricity.
- Axial pret. Forces
MV = Pre-tensioning torque of the locknut [Nm]
FV = Required axial pretension force of the threaded connection [N]
B = Locknut-specific allowance [N], compensates face end relief due to the locking process
A = Constant [mm], includes the calculation factors for the respective thread width (catalogue value)
µA = Frictional coefficient for the end contact surface of the locknut Approximate value μA = 0.1 steel/steel
rA = Effective friction radius for the end contact face of the locknut [mm]
MD = Tightening torque per set screw [Nm]
FV = Required axial pretension force of the threaded connection [N]
A = Constant [mm], includes the Calculation factors for the respective thread width (catalogue value)
µD = Frictional coefficient for the end contact face of the set screw, Approximate value = 0.13
d6 = Dog point dia. of the set screw [mm] (catalogue value)
n = number of set screws
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|Diameter in mm||Clamping screw||calc. factor A||calc. factor B||Perm. axial stress|
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All information is supplied without liability and subject to technical changes. Please observe the operating instructions.
1) The number of the holes corresponds to the number of the clamping screws.
The admissible operating loads specified in the table are guideline values calculated with a safety factor of 1.6 under static stress relative to the minimum yield point, under dynamic stress relative to the minimum alternate strength.
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