Living hinge out of metal

Hey all,

I am working on a project that involves sheet metal and would like to put a bendable hinge in the design. Essentially it would be similar to laser kerf bending.

What would be the best metal alloy to give me the most bends before breaking?

I’ve tested 6061 Aluminum and 4130 Steel. The steel lasted a decent amount before breaking, but maybe there is a better alloy.


Also, if any lawyers have some free time, can you explain to me why all the laser kerf bending projects don’t infringe on Apples patent here.

Hey Nick:

Also, if any lawyers have some free time, can you explain to me why all the laser kerf bending projects don’t infringe on Apples patent here.

I’m not an attorney, but it appears that this patent application has not yet issued and the claims shown in this “publication” may not be allowable in light of the prior art. The claims shown are essentially what the applicant hopes for. The true scope of the claims will be determined during the prosecution of the application. If the patent issues, the claims may be narrower in scope.

Hope this makes sense.


Hello Nick

If you want a metal hinge to last any length of time then you must make sure that the metal never yields. This means for the living hinge design that the flexure of the individual parts is small. You achieve this with thin material and fine strips.

Ordinary steel or aluminium will fail in this application. You need a spring steel or something like beryllium copper or some of the high nickel alloys such as Inconel X750. However, the latter two are very expensive, and beryllium dust is carcinogenic so I wouldn’t recommend laser cutting it.

Regarding the patent, it should get thrown out on prior art. Unfortunately, the US patent system rarely takes any notice of the fact that something has been in the public domain for centuries and just grants patents willy-nilly and lets the lawyers make small fortunes fighting it out in court.

Kind regards - John

Hello Nick
I worked on a personal product for my company Leaf Fly Fishing Equipment. That I used a living hinge in metal for. You can see the product here on my website

It will fail over time but it is a 1000 cycles or so before it fails which is fine for my application. I ended up using a Stainless Steel alloy that was stamped and kept a very thin piece between the outer and inner plates as the hinge. It works quite well if you don’t over flex the part.

Thanks all!


This is what I am looking for. Do you know the exact stainless steel alloy that you used?


Titanium works. Look at the Ibis Bow Ti bike. Uses Ti as living hinge.

Can we private message about that. It is proprietary to my company and I don’t want to put it on a public forum. my email is

I backed this on Kickstarter several years ago and the living hinge is still going strong after daily use and occasionally cracking open a bottle of beer.

The carabiner is a titatnium alloy (unsure which) that is then EDM cut into shape.