How can I cut a 0.75mm radius on a piece of soft rubber sheeting?

[HopperParticipant @hopper]

Posted by clivel on 26/02/2022 18:58:30:

…But to be honest, I don't really see the point of a 0,75mm corner radius, it is barely noticeable without a magnifying glass or close-up photo,

Clive

It's art innit.

[HopperParticipant @hopper]

Posted by Donald MacDonald 1 on 26/02/2022 15:59:53:

Really all I need to know what to Google to find a small die for cutting small (about 0.7mm) radiused corners in soft sheets of leather/rubber etc.

Donnie

Google "radius gauges".

They come in a small set of thin metal templates, each with a corner precision ground to a specific radius. If you remove the 0.7 radius leaf from the set you can then clamp it to your rubber and use an Xacto hobby scalpel knife to cut the radius in the way Clive did above with the more clumsy drill bit as template. Should be eminently do-able. Yes, time consuming. But hey, that's great art.

There will be no magic punch tool that will do the job because any kind of die or punch will need to be carefully lined up to blend the radius into both the sides without a visible join or notch. You would need to have a professionally made punch and die with top and bottom bolsters tied together with sliding guide pins and a fixture to hold your rubber in the correct position vis a vis the radiused punch and die. To get one made would cost thousands of beer tokens.

But unicorn hunting is always fun.

I suppose you could make one out of a standard leather hole punch (google that), the pliers type, and grind away three quarters of the punch so it only cut "a quarter of a hole". But you would have to line it up very very very carefully on each piece so the radius blended into both sides seamlessly. That doesn't seem very do-able compared with the radius gauge and scalpel, but might be quicker.

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