What to do when threads are gone?

Prometheus · Joined: 27 Feb 2008 Posts: 878 Location: Garphyttan, Sweden

The threads on these small, small, small screws in my Super-Takumar 135 are gone, what to do? You might think this blasphemous, but I'm thinking about superglue :p

Sevo · Expire: 2012-12-03

If the purpose of the screws is to lock the barrel against horizontal force, you might get away with screw fastener (a mild variant of superglue hardening when in a thin layer between metal surfaces). If the screws have to withstand vertical force, you'll have to get replacements - regular superglue would prevent any future disassembly, and might propagate into the lens to create fume deposits on the lens surfaces or jam the helicoid or aperture mechanisms.

sichko · Joined: 20 Jun 2008 Posts: 2475 Location: South West UK

Use slightly larger self-tapping screws

OR

drill and tap holes in new positions for new screws.

I've tried the first option - it worked - but I don't have any experience of the second.

kansalliskala · Expire: 2016-12-30

Poolhall · Joined: 25 Feb 2008 Posts: 1296

John (Sichko) is right slightly larger self tapping screws -if you can get them -are the answer, otherwise really you need to re tap the threads and replace the screws which can be done but is really fiddly and slow. I would definitely avoid the superglue method Matthias as Sevo says that would lead to a whole crop of other problems Very Happy

Prometheus · Joined: 27 Feb 2008 Posts: 878 Location: Garphyttan, Sweden

larsr · Joined: 25 Jun 2009 Posts: 272 Location: Helsinki, Finland

You could always also look for a copy with destroyed glass or barrel, and just use it for parts (ie. the screws).

There are also special tools for threading metal, but it might be very hard to find them for so very small screws. i have a regular size set which enables me to make bolts with the exact thread size i want, but it only works if the metal shaft has a diameter around minimum 5mm..

pshute · Joined: 16 Oct 2009 Posts: 15

larsr · Joined: 25 Jun 2009 Posts: 272 Location: Helsinki, Finland

The taps or milling tools I have look like this:

that exact kit is used to make bolts and nuts for tires, but there are similar precision tools available to make smaller threads, too. you hopefully get the idea on how you use them :)