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Is this a worn thread or deliberate

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pgrbff27/01/2021 17:56:05
114 forum posts
16 photos

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

Tim Stevens27/01/2021 18:10:29
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1365 forum posts

My guess is 'BOTH'

Tim

roy entwistle27/01/2021 19:59:40
1321 forum posts

Last couple of threads look to be stretched

old mart27/01/2021 20:02:31
2659 forum posts
176 photos

Tim and Roy both have the answer.

pgrbff28/01/2021 07:12:20
114 forum posts
16 photos

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

J Hancock28/01/2021 08:43:08
536 forum posts

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

pgrbff28/01/2021 09:07:44
114 forum posts
16 photos

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.

Brian Wood28/01/2021 09:26:17
2330 forum posts
37 photos
Posted by pgrbff on 28/01/2021 09:07:44:

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

pgrbff28/01/2021 09:35:28
114 forum posts
16 photos

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?

Nicholas Farr28/01/2021 10:09:27
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2616 forum posts
1225 photos

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

Tim Stevens28/01/2021 10:16:13
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1365 forum posts

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

Howard Lewis28/01/2021 15:52:45
4397 forum posts
4 photos

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

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