ArmaCoil Screw Lock Inserts
Safeguards against loosening under vibration and impact
Free Running Inserts or Screw Lock Inserts
In addition to all the characteristics of the Free Running insert the ArmaCoil Screw Lock insert has one or more of its intermediate coils deformed polygonally.
This serves to create strong resilient pressure onto the thread flanks of the bolt as it passes through. This built in Prevailing Torque of the grip coil positively locks the bolt safeguarding against loosening under vibration or impact.
Bolts can be inserted by hand up to the grip coil, after which some mechanical means, spanner or wrench, must be employed to overcome the prevailing torque.
Colour Identification
ArmaCoil Screw Lock inserts are normally coloured red for identification purposes only, to distinguish them from Free Running inserts. This colour has no other function such as lubricity.
A C.O.S.H.H. sheet for the dye is available on request. Customers requiring this colour to be omitted must specify ‘Undyed’ inserts.
Performance
To obtain the best performance from ArmaCoil Screw Lock inserts it is recommended that only good quality close limit fit, rolled thread, oil lubricated bolts are used. Under no circumstances should ‘black’ (heat treatment scale) bolts be used.
Locking Compounds
The use of thread locking compounds on ArmaCoil assemblies may cause the bolt to lock onto the insert causing the ArmaCoil to withdraw with the bolt. We recommend that no locking compounds be used.
ArmaCoil Flexibility
The ArmaCoil insert has ’designed-in’ axial and radial elasticity. This enables each coil to independently adapt itself and compensate for pitch and angle error that exist and develop between the threaded hole and the bolt as the load is applied.
The load, and the resultant stress, is more evenly distributed over all the threads in the assembly. There is no concentration of stress at any specific point in the assembly.
Pre-load, once induced, remain constant, thus ensuring assembly tightness in spite of shock or vibration.
Cancels out Pitch and Angle Defects
- Ideal contact between all thread flanks
- Equal share of loads for all threads
- Pre-load remains a live factor in the assembly
- Stress intensity reduced
- Fatigue life greatly extended
For more information contact our Technical Department.
