LOAD
RATINGS
The load ratings published in the dimension tables are for axial
loads of constant magnitude under static conditions and have been
calculated with a safety factor of 2 or greater to the material
yield strength. Dynamic loads will stress the parts in fatigue and
therefore should be verified for each application. As a guideline,
the dynamic load should never exceed 75% of the published values.
Calculation
of tightening torque
The axial load of a threaded connection is critical to the proper
function of the equipment, thus the setting of the preload must
be performed with great accuracy. Direct measurement of this variable
is not easily accomplished and most production facilities lack proper
means to do so. To prevent this problem, a calculation must be performed
to correlate the locknut tightening torque to the required clamping
load. |
This tightening torque value
can be easily verified and reproduced by using a simple torque wrench.
Note: The loosening torque should be verified
in applications where angular acceleration/deceleration are very
high. In applications where the mass of the locknut (and its inertia)
could impart a large torque to the unit, and analytical verification
should be made. Nook engineers are available to assist you with
the proper locknut selection. |
Series
MF, MR, MKR, TMF, SFZ
The design of the mounting elements is the responsibility of the
user.
Tools
Appropriate tools for tightening and locating the locknuts include:
- Spanner wrenches (i.e. DIN 1810 A _)
- Universal socket wrench with square socket.
If locknuts and locking screws are fitted
using tool combinations adapted in-house, it is absolutely essential
that the installation guidelines given for the fitting and the specified
tightening torques be strictly adhered to.
Preloading
of bearings and axial clamping
The tightening torque M (calculated as shown) can be applied by
means of:
- The lead screw drive—In this case, the locknut must be prevented
from rotating.
- The locknut—In this case, the screw/shaft must be prevented
from rotating.
- Lightly oil the thread on the screw/shaft.
- Screw the locknut onto the thread, tighten to twice the tightening
torque value M and loosen again. This will prevent any settling
effects.
- Tighten the locknut firmly to the tightening torque M
Locating
the precision locknut
The tightening torque M (calculated as shown) can be applied by
means of:
- Tighten the setscrews (or the cap screws for the MKR product),
evenly and in a crosswise sequence in two steps to the specified
tightening torque (T) indicated in the dimension tables.
- First step, tighten to half the value of T.
- Second step, tighten to the fully recommended value of T.
Removing
the precision locknut
If handled correctly, the locknuts can be reused several times.
In order to remove the locknut:
- Loosen the setscrews (or cap screws for the MKR product).
- Loosen the locking pegs by light blows with a rubber/ plastic
mallet on the outer cylindrical surface in the vicinity of the
threaded setscrew holes. This will prevent damage to the thread
when unscrewing the nut (this step is not required with the MKR
product).
- Loosen the locknut using the pertinent wrench and unscrew by
hand.
- Please make sure to prevent the screw/shaft from rotating while
loosening the locknut.
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