Lego's 0.002mm specification and its implications for manufacturing (2025)

"that familiar click is the sound of a carefully engineered interference fit designed to hold firm but still be easy for small hands to pull apart."

My recent experience calls bs on pulling them apart.

I always remember the small, weird pieces being hard to get apart.

What I don't remember was every kit being made up of so many small, weird pieces.

More than just bricks fitting into each other at a superficial level, it matters how firmly they fit together, and it's one of the areas where LEGO is generally superior to the similar types of bricks.

A detail I didn't realise until I was an adult was the difference between the black and grey technic connecting pins. They look interchangeable, and for a lot of things they are.

But there's a fraction of a mm raised lines on the black one, and it's enough to produce significantly more friction, and that difference is utilised in designs.

And apprently there's now a new version of the black one, and people notice these things, and measure them - this article gives an idea of just how these tiny changes, well below tolerances for some of the "knockoffs", can produce a different effect:

https://ramblingbrick.com/2021/01/27/what-if-they-introduced...

Is it a language mixup, ±0.001mm being called a 0.002mm tolerance? Otherwise I cant figure it out either lol.

After working in automotive, this is less impressive than it appears.

Tons of dimensions on 100k/yr injection molded(and otherwise) parts have similar dimensions. (Although admittedly, after testing in pre-production, I don't know if they are tested again and have drift)

Lego has been making the same parts for decades and their parts are extremely simple. I imagine their 1-off parts for intellectual property based sets do not have this requirement.

I think Lego has a huge incentive to promote this idea that they are high quality to justify the enormous price of decades old technology.