Peculiar Lock Nut

Indeed, especially when there's no description of the nut!

Tim

Pinch nut?

Richard

Thanks Dan

I thought it was going to be one of the "two saw cuts" type (which curiously Google Images is reluctant to reveal), but obviously it is not.

I wonder if the bold was deliberately mechanically bodged with the nut put on too far, and then the nut was wound back into the bodge.

Is it possible a small piece of very hard material (granite chip?) got into the thread and started to jam and then strip it? That's because once you were over the awkward bit the nut and bolt seemed to be matched.

Many years ago, doing some work on a bicycle headset, I had a nut which span along the first 3", then was really tight for about 1" and then span off the last 2".

Careful examination of the threads revealed nothing.

I mentioned it to an old 'un in the local bike shop, and he said that they used to cut the threads with a lathe, and it wasn't unusual for it to have "drift" so the pitch varied minutely - enough to cause the nut to stiffen - at points on the tube.

I have since got a replacement and due to the baseplate being concreted into the ground i have to swap the posts to effect the repair both bolts came away exactly the same requiring a great deal of raunching to undo and both bolts and nuts look exactly the same. I spoke to the technical dept. of the supplier and they confirmed that the nuts and bolts were destroyed in taking them apart and was the reason they were not able to supply replacement parts only complete units. As for how far down the bolt the nuts went it was literally at the end of the bolt.

Richard

Has someone just taken a hacksaw to the bolt. The nut has then been screwed on and the end of the bolt hit with a hammer so the nut doesn't unscrew again?

If you are trying to stop a car being stolen, you want to make it as difficult as possible to remove the bold. If you are just trying to deter casual parkers then Nylok will do the job (although scrap metal thieves might steal the post, I suppose).

No Alan there is no mushrooming of the end of the bolt, a normal nut simply screws on the first few threads up to the damaged section. Nut seems to be damaged just in the middle with a couple of turns of decent thread at each end.

Richard

It looks like a small ball bearing has embedded itself in the threads of the bolt. I'm guessing this is some sort of locking mechanism that allows to nut to go on freely, but the ball bearing "digs in" when you try to undo it.

Is there a small "pocket" inside the nut where the ball bearing would have originally resided? If the pocket had a ramped base this would cause it to jam in one direction.

Do the new nuts have a ball bearing hiding inside?

Tim

Good idea. I was just wondering if it had been heavily peened.

Apologies Tim+ for some reason I am not seeing your posts except as included text in Bob's post. Unfortunately I only have the bolts and nuts off the original post and the one off the replacement post so both are similarly knackered. As I said before the suppliers do not supply spares so I have not got an unused nut and bolt to compare. It certainly seems a possibility though.

Richard

Is that the nut in the van or the nut on the bolt. I'm assuming its a bolt. There used to be a kind of nut which had a kind of one way turn on it, ie if you tried to get them off they bit into the bolt thread harder. Swines to get off. Brian

If its the sort I meant, no the bit like a kind of ratchet is near one end and allows tightening but attempts to move it the other way force it into the thread. Its for security usually. Chubb used to make or supply something like it for security gear. Brian

Brian I get the impression the nut on the bolt (not the nut in the van) is something along what you describe. Undoing it was extremely hard and it felt as if I was distorting metal similarly to a crossed thread but after several turns it suddenly loosens and then simply unscrews like a normal nut for the last few rotations.

Richard

That's exactly what I was thinking.

Picture worth a thousand....