'Knurled Loose Screws'

[Mikegtr]

I have some knurled screws that due to age work their way loose after awhile--the screws work OK but not a tight fit. They are screwed into a metal grub thread. Do you know of any methods that can overcome this?--to make the screw a tight fit but to be screwed in and out at odd times. The threads are pretty fine.

 

[Jake]

Threadlocker - I think there are reusable ones, but I'd guess an ordinary one would work well enough for this (with a bit of top up now and then depending on how often you adjust them).

 

[profchris]

A crinkle washer might work.

 

[Rorschach]

PVA glue makes a very good thread "lock", it provides enough resistance to general vibration but can be broken with hand pressure. CA glue (just a dab) works well but is a little harder to break, sometimes requiring a pair of pliers. All commercial thread locks will be far too strong for your purposes.

 

[Inspector]

Rorschach I can't speak to what you have available but thread locker comes in at least 3 holding powers here. Purple for small screws, blue for screws up to 1/4" (6mm) and red for larger threads. They have them so you can remove the fastener if needed without breaking stuff. Purple thread lock might work for your screw problem. Start with the tiniest amount. If it slips add a bit more next time.

There are adjustment screws that are locked/held a a setting with a spring under the head. Carburetor jets for instance. Can't say if they would be viable without knowing what the knurled screw you have is for.

Pete

 

[Rorschach]

Rorschach I can't speak to what you have available but thread locker comes in at least 3 holding powers here. Purple for small screws, blue for screws up to 1/4" (6mm) and red for larger threads. They have them so you can remove the fastener if needed without breaking stuff. Purple thread lock might work for your screw problem. Start with the tiniest amount. If it slips add a bit more next time.

There are adjustment screws that are locked/held a a setting with a spring under the head. Carburetor jets for instance. Can't say if they would be viable without knowing what the knurled screw you have is for.

Pete

We have the same stuff here, but even the weakest thread lock requires a tool, the OP is talking about finger tight knurled screws.

 

[Jake]

If you have to break it with a tool the first time, it will work well enough for this use afterwards.

 

[Simo]

A few wraps of PTFE tape will do the trick. I use it on guitar tremolo arms that have loose or worn threads, it works great.

 

[AES]

+1 for PTFE tape. Wrap it in the same direction as tightening the thread.

If you must use a thread locker use the weakest grade - IF you can get access to the top of the thread once in position a small stream/spray of very hot water will unlock it.

And nail varnish is a good trick.

Never heard the PVA trick (above), must try that.

 

[Mikegtr]

Many thanks guys for your info--much appreciated.

The knurled screw in question--4 of--is finger tightened and are taken on and off at various times.
They are from a banjo resonator which is screwed onto the banjo hoop. So the reply to member 'Simo' thanks for your advice about the guitar tremolo arm. The suggestion of PTFE tape seems good advice. Will give it a try.