The faceplate on my Seconic L-398 light meter is held onto the head by two screws that screw into threaded brass mounting posts inside of the head. The posts appear to be superglued to the plate they’re on. I managed to break one off.
How do I re-attach the post? Can I just put a drop of cyanoacrylate on it? Or do I need to use acetone (nail polish remover) to clean the bottom of the post and the spot where it attaches before applying the glue?
I’d clean the post, and then carefully roughen the area on the plate where the post sits, using an x-acto blade.
Then, I’d use epoxy, not superglue.
I was under the impression that cyanoacrylate works best on a smooth surface. (Not that I’ve spent much time thinking about it.)
I might have some epoxy around here. I didn’t think of it because of the way it appears to have originally been attached.
I find “Supergules” to be too brittle.
They also don’t adhere to all plastics.
Also, if the plastic is clear, they can fog it.
That said, if it’s not under a lot of stress, Superglue is probably fine.
It broke off because I overtightened the screw and wrenched it off. That said, there are millions of these things out there, and it’s the first time I’ve heard of it happening. As long as I don’t overtighten the screw, and if I’m careful not to drop it on its head, I don’t see why it shouldn’t be ‘as good as new’.
Assuming I do decide to go the superglue route, would I need to clean both surfaces off with acetone?
I’d be worried about the acetone crazing the plastic.
So, I’d just scrape the area and be done with it.
I tried the cyanoacrylate. I decided to use the screw on the other side. It came off. I’ve applied the superglue to that one now. If the posts come off again, I’ll clean the area with acetone and apply epoxy.
Acetone is used to melt/weld certain plastics together; think of a plexiglas display case. Alcohol will clean contaminants off without damage.
Dan
Good to know. (I think the light meter’s case is ABS plastic.)
Acetone readily dissolves polystyrene foam, like foam peanuts, molded packing material, and insulation. Other forms of it like ABS (Acrylonitrile Butadiene Styrene) don’t dissolve as readily but acetone can be used to ‘weld’ it together. Generally avoid using acetone on unknown plastics, and pretty much anything that smells like acetone also.
You can use baking soda powder to instantly solidify cyanoacrylate and to fill gaps. You can sprinkle a bit of soda before affixing the parts, apply superglue and sprinkle again to solidify and fill gaps. You can brush the extra powder away.
While it looks completely solid after applying the baking soda, maximum strength is achieved after a few hours.
I found this to be better than epoxy in many cases, especially plastics which are slightly dissolved by cyanoacrylate.
*Baking soda = Sodium Bicarbonate