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Comment by DannyBee | Hacker News Reader

Outside of cars, roughly every power tool, piece of electronics, cabinet (35mm), etc needs metric sockets or hex keys.

I have built plenty of complex machinery. It's actually significantly easier for me to source 50mm flywheels/pulleys, or v-belts, or whatever, than it is to try to get someone to give me reasonable tolerances on imperial.

While it's true machining is done to thousandths of an inch in the US, most of those machining tools are using chucks/collets/etc whose sizes/TIR/etc is all actually metric.

(IE the 1/2" chuck/collet/whatever is really machined to 12.7mm)

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Good to see that the situation is improving. The more the US imports the more stuff will be in metric, it's unavoidable.

But I'll believe it when the construction industry let's go of the foot and the inch.

A 12.7 mm collet is not a metric collet. A metric collet would be a 12 or 13 mm.

My point was exactly that the construction industry and others already deals in metric whether they know it or not. Yes, they spec 2x4's, and 3/4" CDX sheathng, but every piece of sheathing they use is actually made to millimeter specs, not imperial specs.

This was my point about the collet, too. It's true they collets are not meant to be holding metric sized end mills/etc, but the collet itself is milled using metric sizes. They are not milled to 0.50000, they are milled to 12.70mm.

Good. So that's the source of your confusion then.

I'm glad we got that cleared up. Since the Inch is specified as 25.4 mm you can convert any measurement in Inches into an exact equivalent in metric. But that does not make it a metric size.

Inches: 1/8, 1/4, 1/2, 3/4, 1" etc and various measures in between (5/32nd for instance).

Metric: 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, etc. and various measures in between (5.5 mm for instance).

So you buy your lumber in Imperial measures (apparently except for thickness), and the rest of the world buys theirs in meters (or mm). That's the difference between 'working in Imperial' and 'working in metric'.

Uh, if something is milled to a metric size and tolerances in metric, it is in fact, a metric size, regardless if it happens to match some imperial sizes. There is no requirement that metric sizes be only integer whole numbers, and if you are going to claim that, for example, all lumber purchases outside of the US are done to exact integer metric sizes, that's just false. It may be the construction industry purchases common sizes in MM, but that's not really the same.

If you want only integer or half integer metric sizes, that's something different than "metric sized"

That said, rough lumber outside of plywood/framing lumber is weird in both the US and Europe anyway. Nobody is trying to hit any exact sizes of anything, except that the lumber needs to be able plane down to certain thicknesses. Grading is based on percentage of clear cutting, not on thickness or width or length. If your lumber supplier doesn't give you lumber in thicknesses that can be planed down to the right size, you get a new supplier. Same in Europe.

Lumber isn't 'weird' the sizes make perfect sense, if you're constructing something beyond a picknick table you'll see the logic immediately. Nobody said anything about integer whole numbers.

But I can't seem to get around your mental block that the system you are working in is Imperial, not metric so I'll leave it at this.

Actually, the sizes are in fact, simply odd left-over relics. This is pretty well documented history about how studs came to be nominal vs actual.

Same with hardwood lumber, in fact.

Considering i build about 20 pieces of fine furniture a year, and have built 3 houses, all of which are things "beyond a picnic table", as well as being active in a number of the industry associations that define this stuff (in my spare time), and you apparently know more, maybe you could explain the logic to me.

FWIW: I have no mental block, i actually work in both systems all the time. The whole exercise here has been pointing out your claims are wrong, not about me at all.

Lumber isn't 'weird' the sizes make perfect sense...

If you go to a home depot and ask for something 2x4x8ft, it will not be 2.00 by 4.00 inches or 8ft long, when measured with a caliper. Its weird in the sense that the stated sizes are only approximate, quite unlike hardware or fasteners, wrenches etc.

Those sizes are what they are because of the way lumber is produced. When the mill mills them they're 'true'. But they're also rough. So then they get planed which takes a bit of wood away from all four lengthwise sides.

The keep their name though. This is a convention and a quite confusing one if you're not familiar with the process.

What does it mean to say that "the 1/2-inch chuck/collet/whatever is really machined to 12.7mm"? 0.5 inches is exactly 12.7 mm, so what else would it be machined to?

Yes 0.5 inches would be exactly 12.7 mm but that comes from the way the inch is now defined (which is 1 in equal to 25.4 mm) as opposed to the earlier definition (i.e. 1/12th of a foot (this definition being the older imperial definition). machined to 12.7 mm simply means that the original imperial definition is abandoned for imperial units and although the chuck/collet/etc is still sold as 0.5 inch chuck/collet/etc; when constructing it, it was measured in the SI units of mm for precision purposes.

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