DIY Lens Repair... or not

This is sort of a follow up on this thread.

So I have this Sigma 10-20mm that I paid $100 for because it had been dropped and the AF is not working. It had a cracked section of the body (black arrow) that I replaced ($16). The lens is 100% functional except for the AF. I have run some focus tests, and nothing appears to be out of alignment, aperture works fine, and the glass optics are pretty much flawless.

Sigma/CRIS has quoted $200 to repair the lens, which IMO, is not worth it. The DOF on the lens is huge, and the lens is worth maybe $300+/- if perfect. I don't plan on getting rid of the lens any time in the near to distant future.

When it was dropped, 2 of the three screw holes that holds the back section (black arrow) to the front section (red arrow) were stripped. I have been able to re-thread one of them, but I just can't get the other to re-thread. The joint is the 'seam' between the arrows. Because of this, the lens wobbles at the seam when mounted on camera, and I'm afraid one day it will just decide to fall off at the seam (not good).

Now my question to you DIY'ers out there in POTN-Land;

I have 2 options -
1) wait how long to see if I can get the part that may (or may not) be the problem with the AF and fix it (it's already been 2+ weeks with no response from Sigma/CRIS on the part) and I'm not at this point surei t would be the fix

OR

2) forget the AF, and JB Weld where the screws go to secure the front to the back. This would render the lens unserviceable in the future, but useable as a MF lens (how it is now). It would not really bother me to do that, and while it would affect resale down the road, I really don't see myself selling this lens.

So if you were me, which would you do, and if you would be so kind, why?

Nobody has any advice on this?

I need to see a picture of the area before I can give any advice.

There is another option, given your location - Call Cam-Tek Inc. in Tampa and see what he would charge to fix it.

If its a lens you plan to keep for a long while, why not justify having it services and warrantied for the long haul? I mean if you keep it 10 years, use it once a month for 20 shots. Over 10 years that's 2400 shots, not to mention 2400 opportunities to fail completely. For an additional 200 I think it's best to have it fixed, but that's IMHO.

Mike Deep wrote in post #16197554
I need to see a picture of the area before I can give any advice

Same

Mike Deep wrote in post #16197554
I need to see a picture of the area before I can give any advice.

There is another option, given your location - Call Cam-Tek Inc. in Tampa and see what he would charge to fix it.

I'll go take some pics and get them up.

I tried all the surrounding shops, all want the same as Sigma, or don't/won't work on lenses.

jmcgee131 wrote in post #16197565
If its a lens you plan to keep for a long while, why not justify having it services and warrantied for the long haul? I mean if you keep it 10 years, use it once a month for 20 shots. Over 10 years that's 2400 shots, not to mention 2400 opportunities to fail completely. For an additional 200 I think it's best to have it fixed, but that's IMHO.

I totally hear you. The only reason I'm thinking of going the cheap-a$$ route is because of what lens it is. The DOF on this is HUGE, and the amount of ring movement to go from 3ft to infinity is like millimeters, so even in MF, I feel focusing really shouldn't be an issue.

If it was (just about) any other lens that actually requires significant user input for proper focus, I wouldn't even consider the JB Weld.

I'm also trying to find an alternative to the JB, something that is 'mostly' permanent, but will allow for (easy) removal if the lens needs to be torndown in the future. I've tried to get screws just a hair bigger, which would allow me to just tap into the plastic, but my 3 local fastener specialty places don't have anything that would work.

Here are some pics. If you want something more specific, just say so.
The yellow and red arrows point to the damaged female thread. That's causing me all the problems. I'd have to replace the midsection of the body, and that's something I'm not sure I want to get into. Lots of dissassembling for that.
The grey stuff is the JB that I used to rethread the others, but it isn't happening on that one.
The ring I'm thinking of welding attaches only at those 3 points, and only partially. The next post shows the inside of the last ring, where the screw sits on those 3 points.

BTW, the broken ribbon cable is the part I'm waiting to hear back from Sigma/CRIS on.

The inside of the part to be attached:

What about some type of basic silicone adhesive? That would hold the lens together but still be easy to cut with a razor when you get the new part. It might still move a little due to the flexibility of the silicone but it will hold it together.

If you do decide to keep it mf why not find a set of nuts that fit the required thread then drill out the stripped hole a few mm then glue the nuts in with a small amount of Araldite or something. That way you can at least open it in future.

You could use an epoxy resin to fill the stripped holes and then tap those to accept screws. It's a cleaner repair and it allows for future disassembly.

Maverick7687 wrote in post #16197650
What about some type of basic silicone adhesive? That would hold the lens together but still be easy to cut with a razor when you get the new part. It might still move a little due to the flexibility of the silicone but it will hold it together.

I think any movement/flexibility would be too much.

seall wrote in post #16197655
If you do decide to keep it mf why not find a set of nuts that fit the required thread then drill out the stripped hole a few mm then glue the nuts in with a small amount of Araldite or something. That way you can at least open it in future.

That's a good thought, but the screws are smaller then a #2 screw, and I don't think there is enough 'wall' to drill out wide enough to fit a nut.

Araldite seems to be the British/European version of JB Weld?

Richard N wrote in post #16197681
You could use an epoxy resin to fill the stripped holes and then tap those to accept screws. It's a cleaner repair and it allows for future disassembly.

That's what I've attempted twice with the JB Weld. It worked on one, but the one that's split (red & yellow arrows above) won't do it. I use WD-40 on the screws as a release agent, filled the holes, screwed in the screws, wiped off excess, and let it set for 24 hours. I reassembled, but it still wouldn't hold it tight.

I'm pretty convinced that someone will know of a way to do this. Of course, the easy way is send it in, but I like a challenge, and I'm cheap!

KirkS518 wrote in post #16197722
Araldite seems to be the British/European version of JB Weld?

JB Weld has metalic particles added and is more viscous, you can however use a little denatured alcohol to thin J-B Weld.

You may find the normal non metalic epoxy resin is better at filling the voids and holding onto any keyed areas.

KirkS518 wrote in post #16197722
That's what I've attempted twice with the JB Weld. It worked on one, but the one that's split (red & yellow arrows above) won't do it. I use WD-40 on the screws as a release agent, filled the holes, screwed in the screws, wiped off excess, and let it set for 24 hours. I reassembled, but it still wouldn't hold it tight.

Ah... sorry I missed where you mentioned this already. Can you under cut the the hole in an odd shape so the once the JB sets up it's unable to rotate or pull out?

I would want to remove and replace both parts (barrel and ribbon cable).