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08-23-2011, 06:49 PM   #1
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Good way to repair cracked SMC F filter ring?

I've tried searching around and I know that, in the past, people will typically use a step ring or break the glass out of a garbage UV filter and keep it on the front of their F lens.

So I've got this F 50 and it came with the broken part actually sticking out In the area highlighted in red, the crack goes back that far (it's even with the "line" where the filter ring goes up in size:



The threads look banged up but filters still go on perfectly:



My goals are like so:
-I'd like to at least glue the actual vertical crack back together...with which kind of glue? Won't bother trying to glue the horizontal part.
-Also, I'd prefer if the repair doesn't affect filter or hood use. While I'm not opposed to breaking some glass (goodness knows I have a few crap 49mm filters sitting around) and using it as the new "filter ring," I don't want to glue it on.

What's a good way to clamp while the adhesive dries? Rubber band?

Any other tips or tricks?

Good AF, great IQ, terrible plastic quality. Why did they make the main barrel metal, then skimp on the part that gets a lot of wear? :ugh:

08-23-2011, 07:05 PM   #2
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if this is not helping you sorry. But I usually employ an adhesive named gelX from bestbuy and it does a great job.
08-23-2011, 07:41 PM   #3
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Not sure what to use. There are some types of heavy duty plastic repair glues and epoxy. Prior to gluing with what ever is out there, take the time to cover up the glass tight, such as the likes of crazy-glue and such that have caustic vapors that could stick to the surface.
08-23-2011, 08:36 PM   #4
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1. If you can push down on the cracked portion of the filter ring and the break 'fits' together seamlessly,
2. The break is recent and not much dirt and debris has accumulated in the crack,

Place the cracked area at around 6 o'clock position, place a drop or two of Crazy glue along the crack, guide the separated portion back into the main body of the filter mounting ring with your finger, firmly hold and maintain pressure until the glue sets up. If you are worried about the fumes as MysteryOnion advises, just work in a well ventilated area. Crazy glue is not all that volatile to start with.

Hope this helps,

08-24-2011, 02:21 AM   #5
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A nice fresh opened tube of ethyl 2-cyanaocrylate... it can't hurt to be careful. Just position some painter's tape around, just behind the ring.

Last edited by MysteryOnion; 08-24-2011 at 02:29 AM.
08-24-2011, 02:36 AM   #6
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I would clean up the threads around the break with a dental pick (or finishing nail, or other suitably pointy piece of metal), screw on an empty 49mm filter ring and probably just leave it at that. The empty ring should hold the broken section in place quite nicely and you will have a nice metal thread on the front for screwing on accessories.
08-24-2011, 05:38 AM - 1 Like   #7
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QuoteOriginally posted by ryan s Quote
.....
My goals are like so:
-I'd like to at least glue the actual vertical crack back together...with which kind of glue? Won't bother trying to glue the horizontal part.
-Also, I'd prefer if the repair doesn't affect filter or hood use. While I'm not opposed to breaking some glass (goodness knows I have a few crap 49mm filters sitting around) and using it as the new "filter ring," I don't want to glue it on.

What's a good way to clamp while the adhesive dries? Rubber band?
I like Devcon Plastic welder for general use with plastics; it has high strength, great adhesion to most plastics and good working properties. However it is not very fluid so cracks don't "suck it in". Perhaps someone here knows if the solvent glues* used for plexiglass work on the plastic used for your lens - if so they'd be great for a repair without a glued in filter ring.

Putting a filter with candle waxed threads (or use thin Teflon plumbing tape) to back up your repair while it cures will protect the existing threads and allow future filter use. maybe use a strong rubber band or O ring on the outside to hold pieces in place while the glue cures. Or perhaps you could wind teflon plumbing tape around the broken ring to hold the crack closed while the glue cures.

I'd rethink gluing a filter ring in place as the basis of the repair. A filter ring glued in place will be much stronger than a simple glue or solvent repair and will survive drop damage in the future; in effect, gluing in a metal ring will make a more robust lens (like it should have been in the first place.) Use either a UV filter with the glass removed or a step-up filter if you are worried about vignetting - it is easy to check to see if vignetting will be a problem before you decide.

Dave

* By "solvent glue" I mean the very fluid solvents that are used to "weld" plexiglass (like the corners of plexiglass boxes). These solvents are "sucked into" close cracks; once in the crack they soften the plastic so it welds together then the solvent slowly diffuses away leaving a rigid weld. These are tricky to use - it is usually best to use a hypodermic needle to carefully put the fluid where you want it otherwise it'll run all over the place & make a big mess.
08-25-2011, 12:19 AM   #8
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QuoteOriginally posted by newarts Quote
I'd rethink gluing a filter ring in place as the basis of the repair. A filter ring glued in place will be much stronger than a simple glue or solvent repair and will survive drop damage in the future; in effect, gluing in a metal ring will make a more robust lens (like it should have been in the first place.) Use either a UV filter with the glass removed or a step-up filter if you are worried about vignetting - it is easy to check to see if vignetting will be a problem before you decide.

Dave
I agree this is the best option. You can use a step up ring if you think vignetting could be problematic but metal threads glued on to the plastic threads would make the filter mount so much more stronger.

Thanks,

08-25-2011, 02:11 AM   #9
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QuoteOriginally posted by excanonfd Quote
I agree this is the best option. You can use a step up ring if you think vignetting could be problematic but metal threads glued on to the plastic threads would make the filter mount so much more stronger.

Thanks,
Just for reference..

https://www.pentaxforums.com/forums/pentax-beginners-corner-q/151400-glassles...ml#post1573791

and I agree. Unless it causes problems with vignetting, a metal filter ring is the way to go.

08-25-2011, 06:14 AM   #10
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A metal step-up ring will not cause vignetting.

The lens was designed to accept a filter the size of the step-up ring without vignetting. Since the step-up ring's diameter increases from a point with no vignetting it cannot cause vignetting.
08-25-2011, 07:39 PM   #11
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I'd prefer not to glue a metal ring on (of whatever kind) since who knows if it'll ever have to come off again? But I'll keep a ring on there after the repair. One of my junk filters has what I'd consider a "one time" snap ring...no way to get it out. Another has the typical slots so I'll see what I can do on that.

I know there's some Crazy Glue around here, but I'll take a look for some of the stronger stuff. If nothing else, start with what I have then go to the better glue if needed.

Teflon tape on the threads sounds like a good plan.

Thanks everyone, lots of good stuff
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