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Can be freely, infinitely and exactly positioned. Reliable locking without additional grooves or locking plates. Quick and precise assembly and disassembly.

  • Examples

    Example 1: Tapered roller bearing

    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.

    Example 2: Ball roller spindle

    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.

    Example 3: Friction clutch

    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.

    Example 4: Main spindle bearing

    The locknut ensures a high level of axial rigidity and excellent concentricity on the main spindle bearing in a turning lathe.

    Example 5: Round axis

    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.

    Example 6: Table structure

    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.

    Example 7: Tooling spindle

    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.

    Example 8: Feed drive system

    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.

    Example 9: Piston fixture

    The piston fixture utilizes all the technical benefits of locknuts: Load-bearing capacity, axial rigidity and excellent locking properties.

  • Benefits

    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.

    More success

    • 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

    • Secure
      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.
    • Self-centering
      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.
    • Precise
      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.
  • Function

    Functional Principle

    In this example, based on a type MSF locknut. The principle is illustrated in a simplified diagram with enlarged thread flank play.

    1. Screwing on the locknut

    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.

    2. Spieth locknuts: Self-centring and selfaligning thanks to play restriction

    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.

    3. Tightening and locking

    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.

    4. Higher levels of operational safety

    Spieth benefit: The previously set locking forces are not cancelled by the working load, but are superimposed and therefore reinforced. Put simply: the forces act in the same direction and are therefore added to each other. The optimum solution that delivers improved safety.

  • 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]

    From locknut size MSW > M70

    The tightening torque for the set screw is determined according to the following formula:

    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

Order No.
click for request
Diameter in mm Clamping screw calc. factor A calc. factor B Perm. axial stress
d1 d2 d6 h ISO 4762 MA No. static
ISO-5H c11 Nm mm N kN
M20x1,5 42 42 28 M4 2.9 4 1.344 1560 80
M20x1,5 52 52 40 M4 2.9 4 1.344 936 156
M25x1,5 47 47 28 M4 2.9 4 1.633 1560 102
M25x1,5 62 62 40 M4 2.9 4 1.633 936 196
M30x1,5 52 52 28 M4 2.9 4 1.921 1560 123
M30x1,5 68 68 44 M4 2.9 4 1.921 936 273
M35x1,5 60 60 28 M4 2.9 4 2.21 1560 144
M35x1,5 73 73 44 M4 2.9 4 2.21 936 320
M40x1,5 65 65 28 M4 2.9 6 2.5 1560 165
M40x1,5 75 75 44 M4 2.9 6 2.5 936 367
M45x1,5 70 70 28 M4 2.9 6 2.789 2340 184
M45x1,5 90 90 44 M4 2.9 6 2.789 1404 410
M50x1,5 75 75 32 M4 2.9 6 3.079 2340 267
M50x1,5 95 95 46 M4 2.9 6 3.079 1404 488
M55x1,5 100 100 46 M5 6 6 3.369 2286 504
M60x1,5 100 100 46 M5 6 6 3.655 2286 551
M65x1,5 110 110 46 M5 6 6 3.948 2286 598
M70x1,5 115 115 46 M5 6 6 4.238 2286 645

All information is supplied without liability and subject to technical changes. Please observe the operating instructions.

1) The number of grooves for hook spanner DIN 1810-A corresponds to the number of clamping screws.


Locknuts Series MSW heavy

"The heaviness". Free, stepless and precisely positionable. Reliable securing without additional grooves and locking plates. Fast, precise assembly and disassembly.

Order No.
click for request
Diameter in mm Clamping screw Perm. axial stress
d1 d2 h d4 ISO 4762 MA No. static
ISO-5H h11 Nm kN
M72x1,5 135 60 105 M5 6 6 749
M85x2 160 60 124 M6 10 6 1050
M105x2 190 66 150 M6 10 6 1100
M125x2 215 72 172 M6 10 6 1600
M140x3 240 78 196 M6 10 8 2000

All information is supplied without liability and subject to technical changes. Please observe the operating instructions.

Order No.
click for request
ISO 4028 - 45H d6 MD2) No. calc. factor A
mm Nm mm
M10x45 7 34 8 0.92064
M12x45 8.5 60 8 1.09913
M12X50 8.5 60 9 1.09913
M16x55 12 140 9 1.42613
M16x60 12 140 9 1.42613

All information is supplied without liability and subject to technical changes. Please observe the operating instructions.

2)  Manufacturer's max. permissible tightening torque.

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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