Glasses repair?

[newshound]

On my main glasses (standard wire rim type) the "rivetting" of one of the lens screws is inadequate so that it works itself completely free in a week, although the screw remains captive. It's not a very favourable geometry for applying a thread lock compound. I wondered whether something like clear nail varnish over the head might work. Or supergluing the lens rim to the wire rim near the junction, to reduce the spreading force? Or should I try centre-punching the screw? There is a fairly good dimple in the end.

I have a "repair kit" with lots of screws, selflok nuts, etc which I would use if I had lost the screw but since it is (so far) reliably captive I am slightly reluctant to remove it.

[Martin Brown]

The solution I have used on my titanium glasses frame with a snapped off screw still embedded in it is a small loop of thin copper wire making a spiral binding to hold the frame in the locked position. It fails every three or four years or when I sit on them - which is how the screw snapped in the first place. The titanium frames jump back into shape OK.

Definitely not superglue - it will mist optical surfaces in a most annoying way. Another of its uses is developing fingerprints as the monomer vapour is airborne and condenses out on anything at all.

If you have the original screw why isn't it behaving itself? A spec of locktite before tighenting it would be my suggestion. Using a cocktail stick or needle to get the stuff in the right place.

[Pamela]

Just adding that the manufacturer's technical helpline advise that Loctite

222 is the right one for specs.

Not forgetting that a set of assorted specs screws, which may contain one that's a better fit, can be had for well under a tenner.

[Max Demian]

I know it's not DIY, but opticians are usually quite helpful in this regard, and usually don't charge you anything.

[newshound]

Yes I have a kit a bit like that, but the existing screw is captive in the "head-end" bit and I am slightly reluctant to force it out. The reason it can get unscrewed is that the "dimple" in the thread end has not deformed it sufficiently to prevent it unscrewing.

[newshound]

Yes I did my first repair like that (using paper clip wire) when I didn't have a suitable screwdriver to hand.

Excellent point

It's supposed to be retained by a dimple in the free end, presumably from a customised "press". I could perhaps make it deeper with a centre punch, since it provides a location.

A bit fiddly to clean and degrease the female screw thread. Also, the only thread lock compound I have to hand is relatively viscous.

Interesting to see that Loctite 222 is recommended, so this is "glass friendly" then.

[Martin Brown]

Locktite only activates on exposure to oxygen followed by the high pressure encountered in a tightened bolt.

[Roger Hayter]

There may be different kinds of Loctite, but my impression was that classically it reacted to the exclusion of oxygen, and was kept in a tube/bottle with an air bubble until used.

[R D S]

Correct. It 'sets' when there is no oxygen. ie. you put it on the thread, tighten it up, it locks.