It is a locknut, but to work well in that role it really should have a spring washer or ideally star washer or even a Nordlock beneath it, and as supplied it does not.

Personally I usually un-thread the warning label from the band and captivate it under that nut as well, the deformation of the stamped metal provides some locking action.

However the whole clamp design is poor, there is no 'spring' to the band, so it is not that uncommon to find one where the bolt and nut are tight, but the whole thing can be slid along the pipe, as the band is not gripping well. Something closer to the cord grip in a plug or a saddle clamp would be more positive.

Mike

Petrol engines with old adjustable valve tappets have a lock nut that is used when adjusting the valve clearances. They have no locking or spring washer, and seem to remain tight despite much vibration. A tight lock nut can render the screw solidly secured.

How To Adjust Valves On Your Car - Bing video

Z.

Petrol engines with old adjustable valve tappets have a lock nut that is used when adjusting the valve clearances. They have no locking or spring washer, and seem to remain tight despite much vibration. A tight lock nut can render the screw solidly secured.

How To Adjust Valves On Your Car - Bing video

Z.

I am not sure that that is a good analogy. I don't think that I have ever known one work loose, but I have seen a broken ball-ended stud. Broken as in snapped off.

In the case of the engine, a lock nut would be an extra half-nut on top of the first one.

Back to the question - I am with GTB and Zoomup - it fixes the label. i see no reason why a clamp should work loose without the nut.