Best way to apply Loctite 290


I have several pairs of rimless reading glasses similar to these:
http://tinyurl.com/ybbjy4z
There are 4 tiny bolts that hold the metal parts to the plastic lenses. Invariably, one of the nuts works loose. I have been using needlenose pliers to tighten the nuts, but they work loose.
Some time ago, someone here recommended Loctite 290 (green). I got a bottle the other day, but am unsure how to use it.
The dispenser tip comes sealed, so I used a needle to poke a tiny hole in the tip, but it still comes out in a large droplet that I am afraid will completely drown the tiny bolt and damage the plastic.
I tried dispensing the Loctite with the bottle upright, but was unable to get a tiny droplet to stay on the tip long enough to tough the nut.
Next, I put a couple of drops on a lid and used a toothpick to transfer a tiny amount to the nut. I was able to get the top of the nut to turn green, but I'm not sure I got enough on it to actually penetrate.
Does anyone have any other suggestions? Is a toothpick the right tool? What about a Q-tip?
This has turned out to be more trouble than the glasses are worth. I should just toss them and buy a new pair, but now I'm reluctant to let the glasses win this battle of wills. :-)
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Loctite 290 is a wicking thread locker. Just use your toothpick and let the drop set on the already tightened nut for a couple of minutes. Then wipe off the excess.
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I generally stick to either blue Loctite, or super glue. I put it on the female threads, then screw in the male part. Loctite for stuff I want to get apart, super glue for more permanent fixes. You want it CLEAN. Rubbing alcohol works fine, and won't bother the plastic.
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On 01/26/2010 02:19 AM, Prof Wonmug wrote:

It's usually in a squeeze bottle. Never heard of green. Around here we have blue (temporary) and red (permanent). You put it on the threads before you install the nut. You turn the bottle upside down and squeeze out a couple drops.
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I just use clear finger nail polish. If needed it can still be undone if lense needs replacement. WW
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I've been using clear finger nail polish for many years on applications like this, including gun sights. It's great at holding fasteners stationary and breaks cleanly when necessary. It cleans up nicely with acetone.
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PW-
Locitie is unlike many adhesives. You dont have to worry about it "drying out". Cut a reasonable amount off the tip (the part under the cap).
Loctite is an anaerobic adhesive, it dries in the absence of air so no worries about have a "big hole" in the tip. A tiny hole can often wind up clogged with cured Loctite, as can the cap threads.
As others have mentioned you can apply it with a tooth pick, a Q-tip will waste a lot of the stuff and it's not the best method in this case.
This first "go 'round" might not work. If the threads were not very clean (skin oil) can prevent proper curing of the Loctite and it they work loose again. Clean the parts with a bit of acetone, let them dry and try again. Clean metal parts will lock up just fine.
good luck
cheers Bob
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wrote:

I put some Loctite on one pair last night, then left it overnight to dry. This morning, the glasses had broken right next to one of the little bolts. I guess I used too much Loctite and it seeped down to the lenses and weakened the plastic.
I've tried again with a second pair using less Loctite.
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I watch the Sunday paper ads. Then I pick up reading glasses at a 2 for 1 price.
I break them all the time, even found one pair in the lawn I lost.
No need for fancy Loctite, nail polish, toothpicks (all good ideas, btw) or even Super glue on the offending nut.
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I learned the hard way that Loctite attacks some plastics. :(
I Loctited up about 100 assemblies with a plastic thread.....softened the plastic so threads failed.
cheers Bob
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Another technique you might try is to use a hyperdermic syringe (The one doctors use to give injections). This will give you accurate control of the Locktite. They are not easily gotten hold of due to the war on drugs. If you can convince your doctor or pharmacist that your need is legitimate you may be able to get one. We used them in the past to solvent join plexiglass(acryic) pieces together with ethylene dichloride and capillary action. Joe G
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