Is this a worn thread or deliberate

Is the thread on this hold down worn over many years of use or was it machined like this for easy insertion?

My guess is 'BOTH'

Tim

Last couple of threads look to be stretched

Tim and Roy both have the answer.

Is there a way of cleaning them up so they go in a bit easier?

I would not trust those stretched threads , even less if 'tidied up'.

They're not doing anything critical but I would have no idea how to produce a tapered thread like that. I'm sure I would also struggle to remove the threaded stud from the aluminium handwheel.

Drill a hole through the thread and insert a rod in it for leverage. Heat the aluminium component until it smokes and then work the stub about to unscrew it

Regards Brian

Would it be likely to come out without heating? If possible I would like to preserve the paint and polished finish of these handles. I assume the aluminium might have corroded around the threads making it more difficult to remove?

Hi pgrbff, it is quite possible that the knob has been cast onto the screw, so may not come out at all, in which case you could either cut it off and drill and tap and fit a new thread, or just a plain hole and a plain bit of shank on the new thread and secure with a cross pin, or maybe turn the threaded portion down enough to fit a new thread with the centre bored to a close fit and secure it with a high strength retaining compound such as Loctite 638 and pin it crossways also if you want reassurance for it to hold.

One question, does it have to be slightly tapered?

Regards Nick.

Edited By Nicholas Farr on 28/01/2021 10:13:08

The thread can be sorted by running a tap down the thread. Just be sure before you start that the thread is properly identified. If the machine it came off is British and pre 1960, it may well be Whitworth, if later or USA-made it will be Unified or American. If continental (eg Germany) it will be a Metric thread.

A wire brush will be helpful, too.

It wasn't made that shape - the thread was parallel and has been messed with in its past life.

Cheers, Tim

Looks as if it might have come from a machine tool, such as a surface or cylindrical grinder.

My guess is that the handwheel was cast round the stud. So replacing it means, having established quite clearly what the thread is (Try measuring close to the handwheel where it will be relatively unworn ) drilling out tapping, and inserting a new stud.

The new stud should be secured with an anaerobic adhesive, and possibly also secured with a taper pin, for good measure.

Howard