I recently purchased some 2cm / 0.75 inch keychain Rubik's Cubes. They are the old ones and come in little black boxes. The problem is that they break virtually as soon as you touch them. The spider literally shatters. I don't have a problem with the seller as he informed me this was likely to happen. I rather hoped a few would be ok but all 5 have broken. I wondered if anyone here had any information about why certain ones break whereas other seemingly identical ones can stand years of use. I have 2 which came in the same boxes many years ago and they still work fine. I am not sure if I have tried the ones on a card and wonder what they are like. To me they look the exact same product. I have tried some more modern ones but they are extremely stiff and poorly made.

maybe since they're so old and havent had any use they have become extremely brittle to the point that they cant stand any movement, whereas the other ones you had that worked were used more and were less brittle. Maybe thats a possibility?

There was some past discussion about spindles which were transparent or close to transparent. Some manufacturers may have used polycarbonate or perhaps even polyester resin. In my experience the spindle of a 3x3x3 is the most likely part of a cube to break and a micro-cube would have the thinnest and most likely to break spindle. Polycarbonate is often used in rapid prototyping.

I'm fairly certain that official cubes have nylon spindles but I have seen clone cubes with semi-transparent spindles and they often broke. A couple of Ideal Toy cubes broke on me... perhaps the petroleum jelly attacked the plastic of the spindle.

It's also possible that there was simply a bad batch of spindles and the problem was aggravated by the tiny size. Perhaps one could construct a "Super Deluxe" cube using aluminium spindles. I have a white cube that is 37 mm to an edge and it's the smallest cube I have that handles and turns well.

Maybe this could be a possible project:

Use two very small pieces of aluminium pipe and create an ersatz spindle. Tap some threads for the screws or put in rivets. It would be a lot of work though.

Thanks Mark. When I bought my first micro cube (2 cm) over 20 years ago I really wasn't expecting much. It worked extremely well however and stood up to my (pretty slow) speedcubing. For some time now I have been trying to get some more for transformation purposes.

I bought these cubes from the same seller (I believe so) quite a while ago. I bought three. Two of them I opened one after another, and both just fell in pieces after one turn. I decided not to open the third one...

I also got some normal size cubes from Japan a long time ago that had similar kind of the very brittle semi-transparent center spider. I had a post with photos about that one.

I purchased a big lot of 20mm Rubik's Cube micro keychains for fun, maybe 25 of them. Several of them broke the moment I turned them. Others lasted a couple of twists.

I don't think the 20mm cubes are really suitable for anything other than static decorations or keychains. They're certainly not durable enough to play with on a regular basis.

The ones I bought years ago have stood up to quite a bit of wear and tear. I even used them for speedcubing for a while. I lubricated them with petroleum jelly (against all advice) and they still work fine.

Another thing that might make them brittle is overheating. Yours might have been stored in a hot shipping container for a long period of time. They might even have experienced a fire or something like that.