SPIETH Precision Locknuts: vise-like hold on high speed mechanisms

SPIETH Precision Locknuts

Precision Locknuts by SPIETH

Supports Extreme Thrust Loads

  • Positive locking without washers and keys

  • Especially suited for high speed and/or high dynamically-loaded spindles or mechanisms

  • 360° contact around the thread flanks guaranteeing a vise-grip locking effect



Adjustable locknuts

Spieth Adjustable Locknuts adjust, preload and secure bearings and other machine components on shafts and spindles with a high degree of stiffness. They permit the correct setting of the axial preload of bearings and ensure that the working loads are carried safely. The locknuts are secured positively without additional components, keys, or extra machining.

The high load-carrying ability of the locknut is achieved through full 360° contact around the thread flanks guaranteeing a vise-grip locking effect. This contact around the full circumference ensures the the locknut will not loosen, even when subjected to extreme shock loads. This is an important feature, since locking with many commercially available locknuts relies on only one or a few "pinch" points on the circumference of the thread.

Another advantage of the SPIETH Locknut is the feature of aligning its contact face either with zero runout or, if necessary, adjusted to suit inaccuracies of in-line connecting components, thus the stack-up of mating parts. Spindle runout, due to uneven bearing loading, can therefore be eliminated. A high degree of accuracy can be maintained even when repetitive tightening and loosening are required. The benefits of SPIETH Locknuts offer solutions for a wide range of general precision, heavy machinery, and equipment applications.


The unique locking capability with high stiffness and accuracy is excellent for spindle applications - especially suited for high speed and/or high dynamically-loaded spindles or mechanisms.

Thread sizes are equivalent to the standard bearing locknut series N/AN American Standard National Class 3 Fine, and metric sizes to ISO 5H fit. The widths approximate two N/AN locknuts. SPIETH SERIES MSW heavy-duty ADJUSTABLE LOCKNUTS are applied in conjunction with combined needle and roller thrust bearings, plain thrust bearings, or taper roller bearings, on ballscrews, work drives, bevel gears, and other high-thrust-carrying components.




Two axially-arranged radial grooves, one from the outside and one from the inside, result in a diaphragm-like cross section which gives the nut a predetermined axial elasticity. The internal groove divides the nut into a clamping and locking section. Depending on the nut size, three to eight axially arranged socket head cap screws are used to clamp the sections together. This eliminates the thread flank clearance between the shaft thread and locknut and allows for shockproof locking. Depending on the size and load capacity, two types of locknuts are available. For all MSR, MSA, and MSW sizes up to locknut 70.46, the axial bearing preload is adjusted by tightening the locknut through direct face contact. Size MSW 70.60 and larger use a number of clamping screws to reduce friction on the nut contact face, thus allowing for accurate preload adjustment.

MSR Locknuts are made of alloy steel, MSW Locknuts are made of heat-treated alloy steel. Both Locknut series have black oxide finish for rust protection. The nut thread is manufactured to American Standard Class 3 Fine or ISO H5 fit. The contact face is machined square to the threads within .0002 in. Both types of locknuts are symmetrical in construction and are manufactured from solid stock. Threads and contact faces are machined by special single-point threading tools in one set-up to guarantee squareness. Balancing, therefore, is required only in extreme high-speed cases. The SPIETH Locknut's main feature is its capability to lock onto the threads over the entire 360-degree circumference.



Preloading Nuts: All MSR, MSA sizes, and MSW sizes up to 70.46
These nuts have holes or slots on the outer diameter, which are suitable for available radial spanner wrenches. When the nuts are used in recessed applications, a tubular face spanner wrench with exposed prongs MSW series and pins for MSR or MSA series is recommended.

Preloading Nuts: Size MSW 72.60 and larger
These nuts are screwed into position either by hand or by an available hook spanner wrench and locked into position without making face contact. Hardened clamping screws are then used axially for preloading; which, after adjusting, are secured in position by radial radial set screws through aluminum slugs.

Mating Component

Mating Thread
The shaft thread must be manufactured to American Class 3 "fine" or ISO Class 4h if applied for high-precision spindles or class "medium" or ISO class 6g for general applications. Surface roughness must be low to avoid compaction during shock loads.

Mating Parts For Locknuts Up To Size MSW 70.46
The preload torque is applied directly to the nut. However, means must first be provided on the shaft to counter the torque. For optimum results, the accuracy of components assembled between the shaft, shoulder, and locknut contact face (bearing, gears, spacers, etc.) must be parallel and square to the bore within .0005" or better. In addition, the surface finish of the assembled components should be a minimum of 32 mico-inches or better in order to avoid surface compaction under load.


Mating Parts For Locknuts Size MSW 72.60 and Larger
The axial preload applied through the hardened clamping screws must act directly on the bearing face of soft surfaces. A thrust ring at least thick as the bearing race should be sandwiched in between the bearing and locknut. The ring must be hardened, parallel, and square as specified above. If the design requires other components such as gears to be placed between the bearing and the locknut, again the accuracy must be held as specified above to avoid excessive deflection and surface compaction. If these components are hardened, the clamping screws can press directly against them without a thrust ring.



SPIETH Precision Locknuts Catalog

SPIETH Precision Locknuts

PDF Catalog 2.1MB


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Shane Hatfield
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Customer Service



Advanced Machine and Engineering