Daf demands accuracy
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IN All Daf vehicles are now fitted with screw connections treated with a lubricant. These "dipped connections", says Daf, allow a more accurate tightening to the specified pretension.
This development, explains the Freight Transport Association's Engineering Digest, No4/ 87, does not apply to Leyland vehicles.
In production, says the FTA, galvanised nuts and bolts are wax dipped whereas phosphated nuts and bolts are oil dipped.
Dipped connections mean that it is possible to reduce the tightening torque to a lower value at the same pretension but, because of the resulting narrower thread in the torque values, Daf has warned that a higher accuracy in tightening is necessary and has recommended the use of a torque wrench. • To obtain the correct pretension when nuts and bolts are re-used, it is important that the screw thread is thoroughly cleaned.
• One drop of lubricant should then be applied to the first coil of the thread and one drop to the abutting face of the nut or bolt.
• Daf stresses that the only lubricant permitted is engine oil.
When applying locking compounds in combination with dipped nuts and bolts, the procedure is: 1, Thoroughly clean and degrease the nuts and bolts (this applies equally to new fastenings); 2, Apply the specified locking compound to the screw thread; 3, Apply one drop of lubricant to the abutting face of the nut or bolt; 4, Tighten to the specified torque.