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Comment by fletchowns | Hacker News Reader

You're not thinking about all the designs, tooling, manufacturing facilities, etc to build all that stuff though. That's where the real cost is.

> Would it be a huge deal to round that to 40mm by 90mm?

It actually would be a big deal to round things like that I think. Whole designs would need to be updated to take into account the new dimensions of things.

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Any manufacturing component which cannot easily be adjusted to a slightly different measurement is poorly designed, in my opinion. I would expect that much of these tools could be tweaked to produce things in metric measurements. If not, the dimensions can simply be converted and re-labeled. If something manufactures a square piece of metal that is 3" by 3", is it a huge deal to just document it as being 76.2mm by 76.2mm?

> Any manufacturing component which cannot easily be adjusted to a slightly different measurement is poorly designed, in my opinion.

Imagine all of the parts in a car engine. Everything fits together perfectly. Engine mounts line up in the right places. It all has to be very precise.

Now imagine you take all those parts and round them off a bit. Nothing much, just a mm here and there. If you try to put the engine together with these parts, it's not going to work at all.

Also consider that you can't just simply convert the units. Take a 5/16" socket wrench for example. Nobody makes a 7.9375mm socket wrench.

While I think the rounding would work with lumber, I definitely don't think it would work with things like car engines. For such precisely-measured components, converting to a metric measurement with the correct significant figures should be fine.

Repair shops can maintain tools for both systems (they already have to). For converting, I mean the dimensions of a component, not tools and fasteners that need to work with tools. Those would likely take a "metric only going forward" approach.

Rounding from 38 to 40 is a difference greater than 5%. Some applications might support that, but I'm sure there are plenty that won't. For example, wood joints have very small tolerances.

More manufacturing is done in China, and the factories are used to the different international markets because they're often parts suppliers for foreign companies that have their designing done in various countries. So they're well equipped to make things in either inches or mm.

You're overstating it, there are only 2 other countries in the world that use imperial units

> You're not thinking about all the designs, tooling, manufacturing facilities, etc to build all that stuff though. That's where the real cost is.

A lot of them are already metric.

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