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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 14th Feb 2003, 7:54 pm   #1
rmorti
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Join Date: Dec 2002
Location: Winchester, Hampshire, UK.
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Default Stripped Threads in Bakelite

Hi

A quick one out of recent experience with a DAC90A...a definate design shortcoming (daresay in other sets also) is the tapping of threads for bolts directly into the bakelite, instead of moulding in a brass threaded insert. Relies on thick bushes and a fair length of thread to prevent the thread stripping, but...these things happen (one of the speaker mounting points on my set)!

An almost ideal fix is to use a short length of plastic cable tie, trimmed to a suitable size and thickness, inserted into the stripped hole to give the screw something to bite on. Has to be trimmed so as not to unduly stress the mounting bush as the screw's done up, of course, but the squashy plastic/nylon used provides just the right amount of grip.

Richard
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Old 6th Mar 2003, 4:18 pm   #2
rob
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Default Re: Stripped Threads in Bakelite

PTFE tape also works. It is used by plumbers for sealing pipe threads and can be obtained from B&Q, Wickes, etc.

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Old 6th Dec 2003, 9:37 pm   #3
JHGibson
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Join Date: Apr 2003
Location: Salt Spring Island, BC, Canada
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Default Re: Stripped Threads in Bakelite

When faced with this problem in the past, I just retapped the hole to the next larger standard screw thread. You will need to finish the threadcutting with a blind hole type tap after the first cut with a standard tap. In either case do not force the tap with higher torque than that you began tapping with, otherwise you might have bottomed the tap in the meantime and the increased forces could split the bakelite and create an even bigger problem! This is one repair job where experience really counts. I recomend you drill blind holes in a piece of scrap bakelite and practise first.
If you do not want to use a larger screw, you could fill the stripped hole with Araldite epoxy and after it sets then use a appropriate drill and tap to the original size.
One repair method that I plan to try on my next stripped thread is to fill the hole half full with Araldite with the entire hole wall wet with it and then run the original screw fully in and then let the epoxy set. The screw will need a faint hint of oil on it to act as a release agent so the the screw is not permanently glued in! This is only a thought and is totally untried. Did anyone try this already?
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Old 6th Dec 2003, 10:29 pm   #4
Tim
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Default Re: Stripped Threads in Bakelite

Car filler works very well too, and like Araldite can also be drilled and tapped. It may be coloured/painted afterwards if required.
Regards
Tim
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