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I've noticed that prescription eye glasses frames are often made from metal that is quite rigid. It's surprisingly difficult to bend the metal, despite how thin it is. And if it does bend, it doesn't seem to weaken much when bent back and forth.

Is there a certain kind of metal that is typically used for making prescription glasses frames?

Examples that come to mind:

  • High-grade aluminum or aluminum alloy
  • Stainless steel (can it be painted?)
  • Titanium
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    $\begingroup$ Previous ones I had were the nickel-titanium alloy (marketed as "titanium" and "super flex"). Feather light and unbelievable elastic range. If they feel rigid it's probably something else, IMO. $\endgroup$
    – Pete W
    Sep 13 '21 at 13:33
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    $\begingroup$ I've been wearing metal framed glasses for thirty years and haven't come by frames that were rigid that you could also bend without damaging. I think you are doing something like not using the same axis of bending or lever arms of inconsistent length (too short a lever arm when bending and too long a lever arm when flexing, or are just unaccustomed to the ductility of metal in general. Or not noticing the springs in the joints. $\endgroup$
    – DKNguyen
    Sep 13 '21 at 13:43
  • $\begingroup$ I've been wearing metals frames for decades, and the ear pieces, at least, have a good amount of flex to them. You might check other vendors. $\endgroup$ Sep 13 '21 at 21:37
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There are many different materials that can be used for modern eyewear.

Based on the following table (I put it together from online searches, its not from a single site, although the content is repeated - also I haven't managed to complete it), probably the ones you are looking at are either:

  • Berryllium alloy
  • some memory alloy (usually titanium based Ti e.g. Flexon)
description lightweight ($gr/cm^3$) strong corrosion resistant hypoallergic cost flexible usage
Titanium +++ (4.5) +++ + + durability
Monel (usually nickel-copper alloys) (8.8) ++ + (have a coating to protect the skin) people who spend a lot of time in or around salt water
Beryllium alloy ++ (1.85+?) + +++ ++ people who spend a lot of time in or around salt water
Stainless steel + (8) + ++
Flexon (Ti -Ni shape memory alloy) + (6.5) + + + +++ active kids
Beta titanium (Ti+ traces Al+V) ++ (4.5) + + + +++ active kids
Aluminum + (2.7) ++ ++ + ++ high-end frames
Magnesium + (1.7) high-end frames

NOTE: the above is not a authoritative table. It is my interpretation from online searches.

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    $\begingroup$ Where did your table come from? $\endgroup$
    – hazzey
    Sep 13 '21 at 13:44
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    $\begingroup$ Not stainless. It would need to be cold worked for strength and cold work makes austenitic SS magnetic. I checked several pair - no trace of magnetism. Roughly; 304 will get to about 20 % and 316 about 40% as magnetic as carbon steel when heavily cold worked. Very interesting question, however. $\endgroup$ Sep 13 '21 at 14:04
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    $\begingroup$ Beryllium can't be used for eyeglasses. It's brittle and it's toxic enough that it should only be handled with gloves. Perhaps the original source of this chart referred to beryllium copper alloy, which would indeed be resistant to corrosion from salt spray. $\endgroup$
    – MTA
    Sep 13 '21 at 20:31
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    $\begingroup$ @hazzey Searching for the unique phrase "people who spend a lot of time in or around salt water" in quotes yields these two sites with nearly identical tables. However they only have x/blank instead of +/++/+++, so the original source might be somewhere else. $\endgroup$ Sep 14 '21 at 1:29
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    $\begingroup$ Anecdotally Ti-based frames are good for people whose sweat corrodes other frames (salty and/or copious sweaters, or very active people). I've found greenish corrosion on some of my sunglasses, suggesting a significant amount of copper in those alloys $\endgroup$
    – Chris H
    Sep 14 '21 at 10:07

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