Lock Nuts are primarily intended to secure the location of bearings but also they secure other machine parts (e.g. gears, sleeves, bushings etc).
Additionally lock nuts are also frequently used as a device to mount or dismount bearings, (e.g. to remove bearings mounted on withdrawal sleeves).
For securing lock nuts that are being used to fix a bearing and to protect them from becoming loose lock washers or for larger nuts locking clips must be used.

NKE - lock nuts up to a bore reference number 40 (bore diameter 0 200 mm) are produced with metric ISO - threads as standard.
Larger lock nuts, (e.g. from a bore reference number 41 upwards), have metric ISO - trapezoidal threads as standard.

Lock Nuts DIN 981

Locking washer & Locking clips DIN 5406

The standard lock nuts with metric ISO - threads are identified by the symbol KM.

Example: KM 30
Standard lock nut,
with metric thread M 150x2. Outer diameter 195 mm.

Additional to the standard nuts there also exists a narrow series of lock nuts, namely KML. Lock nuts of the narrow series have reduced outer diameters, whilst all other dimensions remain as for the standard KM --lock nuts.

Example: KML 30
Lock nut of narrow series, with metric thread M 150x2. Outer diameter 180 mm.

Larger lock nuts with metric ISO - trapezoidal threads are designated by the symbol HM .. T.

Example: HM 52 T
Standard lock nut,
with metric trapezoidal thread Tr 260x4. Outer diameter 330 mm.

There is also a narrow series of larger lock nuts available with reduced sectional height:

Example: HML 52 T
Lock nut of narrow series,
with metric trapezoidal thread Tr 260x4. Outer diameter 310 mm.

Depending on their size, lock nuts have either four (see figure a) or, in case of larger lock nuts, eight (see figure b) slots equally spaced around their circumference.

These slots provide better handling during mounting and dismounting, but their main function is the fixing point to apply the required mounting tools, (e.g. hook spanners).
These slots must also accommodate the lip of the locking washer, or for larger nuts the locking clips.

Larger lock nuts also have tapped holes in one face (figure b). Their function is too accommodate the screws engaged in securing the locking clips.
Additional to the standard lock nut designs previously mentioned, nuts are available in several more variants, such as:

Stainless steel lock nuts.
Lock nuts with zinc or phosphate coated surfaces.
Lock nuts with left hand threads Lock nuts with inch sized threads.
KMT and KMTA type.
Hydraulic lock nuts, NKE will provide detailed information on request.
Larger lock nuts of series HM, T and HML. T series are secured against loosening by applying locking clips (MS, see figure b).

Locking clips are supplied complete with hexagonal head screw and a spring washer.

All information courtesy and copyright NKE Bearings Austria www.nke.at

Lock washers are supplied in either stainless steel, phosphated or zinc coated, they provide a means to secure bearing "Lock Nuts" from the effects of rotational forces or vibration. The tabs are folded into one of the cut outs in the lock nut once the nut is tightened, the innnermost tab is located into a keyway on the journal end thus tying the two components together. (figure a)

Larger lock nuts of series HM, T and HML. T series are secured against loosening by applying locking clips (MS, see figure b).

Locking clips are supplied complete with hexagonal head screw and a spring washer.

All information courtesy and copyright NKE Bearings Austria www.nke.at