- Lock Nut: Alloy Steel.
- Finish: Phosphated and saturated with oil.
- Locking Pin: Sintered Steel.
- Grub Screw: Type MT6SS short pin, (DIN 915, 45H).
Thread Tolerance: 5H: ISO 965/3.
Axial Runout Locating Face / Thread: 0.005 mm max.
Recommended Tolerance for Mating Shaft Threads: 6g: ISO 965/3.
Dimension standards to ISO 965/3.
Lock nuts are used to locate bearings and other components onto a shaft or adapter sleeve.
They are also used for mounting bearings on tapered shaft seats and dismounting bearings from withdrawal sleeves.
Lock nuts have to be secured to prevent unintentional loosening.
This is done, either by a locking device that engages a keyway in the shaft or key slot in the adapter sleeve, or by a locking mechanism integrated in the nut.
Lock nuts with an integrated locking mechanism reduce the cost of the shaft as no keyway is required.
Installation is also quicker and easier because no separate locking device is necessary. However, the loosening torque of these lock nuts requires more attention.
Lock nuts are locked on the shaft (sleeve) by friction which varies (with the loosening torque) as a result of the accuracy of the tightening torque of the grub screw (locking screws), the surface finish of the shaft (sleeve) thread, the amount of lubricant on the thread, etc.
The lock nuts should be properly mounted and there should be only a limited amount of lubricant on the thread.
There are three locking pins equally spaced around the circumference of the nut to lock it onto the shaft.
The locking pins are pressed into the shaft thread with grub screws.
The end face of each pin is machined to match the shaft thread.
The holes for the locking pins and grub screws are drilled at an angle to the shaft thread to avoid backlash.
Intended for applications where high precision, simple assembly and reliable locking are required.
They should not be used on shafts with a keyway or on adapter sleeves with a key slot.
The locking pin can be damaged if it aligns with a keyway or slot.
These have a full cylindrical outside surface and a different thread pitch than KMT nuts for some sizes.
They are intended primarily for applications where space is limited and can be used to establish a gap type seal.
Installation and removal
There are holes around the circumference and in one side face, tightened with a pin wrench, a pin type face spanner or a tommy bar.
Lock nuts can be reused, provided they are not damaged.
A new lock washer, locking clip or locking plate should be used each time the corresponding lock nut is installed. Designed for frequent installation and removal.
These lock nuts should be locked in two phases:
1 Tighten the grub screws carefully until the locking pin engages the shaft thread.
2 Alternately tighten the grub screws with a torque wrench until the recommended torque value is achieved.
These lock nuts are adjustable. The three equally spaced locking pins enable the nut to be accurately positioned at right angles to the shaft or they can be used to adjust for misalignment between the abutment surface and the adjacent component.
Adjustments can be made using the following procedure:
Loosen the grub screw at the position showing the greatest deviation; tighten the two remaining screws equally; re-tighten the screw that was loosened; check the accuracy of the installation with a dial gauge; Repeat the procedure if the result is not adequate.
When removing the lock nuts, the locking pins can still engage the shaft thread even after the grub screws have been loosened. Using a rubber hammer, tap the nut lightly in the vicinity of the pins to disengage the pins from the shaft.