Damaged threads on lenses.

[uddhava]

I have some lenses with slightly roughed up threads for the filters and some on the screw mount (M42).
Does anyone have any solution for fixing this problem?

[cooltouch]

Mine is the old and slow method. You know those tiny file sets you see that you can buy for pretty cheap, like $5 or less sometimes? They come with a variety of file shapes. One of the angled ones will usually be narrow enough to fit into the threads of a lens or device/filter that threads into a lens. If the lens diameter isn't too small, these straight files can work. I'm cleaning up the threads on a Tamron mirror lens right now using one of these files. It has an 86mm front filter size, I believe. I started working on it a few days ago and set it aside after getting the threads straight enough where the hood would thread on, albeit with some difficulty. I'm gonna work on them some more until it threads on easily.

These straight files will work just fine on male threads, such as M42 lens mount threads.

Somewhat less common are files that still have the same cross-section but that are curved. These are the ones you want for more normally sized lenses, say in the 49mm - 72mm range.

I have a set like this somewhere (my tools are still in boxes from a recent move):

http://www.micromark.com/5-piece-diamond-riffler-set-fine-grit,7751.html

I don't know if any of them will be narrow enough, offhand.

Micromark also has this set of riffler files:

http://www.micromark.com/10-piece-riffler-file-set,6789.html

I have this set also (in a box somewhere), and I'm pretty sure there is at least one file in the set that's narrow enough for filter grooves.

You might look around Micromart some more. They have all sorts of stuff, you might find something that'll work better for your needs.

[Lloydy]

For male / external threads you can buy 'thread restoring files' - which will do the M42 thread on a lens as long as the file has a side that has a 1MM pitch file on it and is for Metric threads so the right angle is maintained. Thread files are multi sided. This is a decent description of how they are used -
http://www.webbikeworld.com/motorcycle-tools/thread-file/

You can get internal / female thread files ( you can get files with both on the same file ) as well, and again you have to determine the pitch of the thread, which I think is 0.5mm for filter threads.

I also use the riffler files that cooltouch recommends for internal threads ( being a maintenance engineer I've got a set of external thread files but no internal ones ) so I use what I can and rifflers do a decent job. I've also dragged the tip of a craft knife blade down the damaged part of a thread with good results. I then use an old filter with a tiny bit of oil on the thread and work it back and forwards until it's free.

[uddhava]

Thank you both!
I will try the knife first since I have it and report the results.
Maybe I can buy those files on ebay.

[DConvert]

[uddhava]

Thank you for all of the detailed knowledge, but finally I ended up filing the offending threads completely off! Sometimes using a hacksaw as the file!!!
Needless to say I will not show photos of the repair job. At least it is unnoticeable when the lens is screwed on to the camera. It did work though.
The lens is a Soligor 4.5/200 which cost $14. I bought it because of it's light weight.
Now however I see that the lens focuses way beyond infinity and does not focus at it's minimum
focusing range. That will be a new topic.

[DConvert]

[uddhava]

Finally I have figured out that the lens was wrongly advertised as m42 when it was really a T mount (m43)!
I think putting a T to eos adapter on it will solve the infinity problem of my now reduced in value lens.


Yes that solved the infinity problem. Sorry I treated it so roughly. Also I should have mentioned what lens it was,
perhaps someone would have figured out the problem. Mistake by the camera shop was the culprit.

[cooltouch]

If the threads are buggered up at all, just turning a T-mount onto the lens and back off a few times will chase the threads for you.

You know, having a T-moun lens instead of an M42 is not necessarily going to negatively impact the lens's value. I mean, when it was (supposedly) M42, it would have worked only on M42-mount cameras. But as a T-mount, the universe of 35mm SLRs has opened up for you and the buyer . . . if you were planning to sell it, that is. I have a few T-mount lenses that I treasure and I'm thankful that they're T-mount because of the versatility this provides.

This being a Soligor 200/4.5, I don't really see how a T-mount system is gonna negatively affect its value.

[uddhava]