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Comment by jacquesm | Hacker News Reader

That's a typical case of theory and practice.

Yes, in theory the US is a country that supports metric. In practice, go and ask anybody in the country outside of the military for the following:

- An M10 bolt

- a 16mm wrench to drive it with

- a 3 meter long 50 mm od pvc drainpipe

- a tape-measure that measures only in metric

- a highway sign that is posted in km

And so on. See how many people can point you to any of these.

Then try this:

- a 3/8th " bolt

- a 9/16th " wrench to drive it with

- a 10' long 2" od pvc drainpipe

- a tape measure that only measures in Imperial

- a highway sign posted in Miles.

The petition is dead on in the way the US approaches the metric system, in practice it is imperial all the way. As long as the practice doesn't change what the technical situation is won't matter one bit.

The only way to get out of this is to change the law, and to deprecate Imperial in favor of metric.

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Have you ever been inside of a hardware store?

Every hardware store I've ever been to has a section for metric. Our lab, for instance, keeps a supply of bolts, and as far as I remember /only/ has metric.

Also every socket set I've ever used has a metric and standard set.

Why would you care about road signs? And why would you care about a tape measure that is /only/ in metric? The second one seems kindof silly.

The only thing I know of that isn't available commonly in metric sizes are machining tools like mills. As far as I know, machining is always done in "mils", or thousands of an inch.

Or if you happen to ask anyone who works on a vehicle that isn't from one of the American manufacturers. My Toyota used all metric, AFAIK, and all of my motorcycles have used metric. I can't say I've ever even used the standard set of tools that came with my toolset (which had both metric and standard).

Toyota is weird, in that all of the nuts & bolts on their cars are metric, but their tolerances in the factory service manual are listed in thousandths of an inch. I did a double-take when I saw the deck flatness tolerance of ".002" for my car, for example.

My Ford car is all metric as well.

> Have you ever been inside of a hardware store?

I believe so. Maybe a couple of times. Or maybe I practically lived in one for a couple of years.

Would this do for you?

http://pics.ww.com/v/jacques/trips/jansvisit/?g2_page=6

Yes, there is a section for metric in the hardware store.

It's the bit at the back with about 1/2 the sizes missing and only the stuff that you don't need in stock. I've had a machine shop in Canada (which officially had metric) and it was quite hard to get metric stuff. So hard that in the end we standardized on Imperial. In the US it was way worse.

Socket sets have standard and metric. Metric mostly for working on Japanese or European cars. But the most tools 'at hand' will be imperial. Maybe your experience is different but I've had plenty of bolts on my Japanese car wrecked by a shop putting imperial tools on them and plowing ahead. Works especially good if you use airtools, instant roundness.

You care about road signs because they're a sign that you really are standardizing. If your road signs are still in Miles then you're not a 'metric' country.

And you care about a tape measure only in metric because that's all you use in a metric country.

Machine tools - of which I owned a small fortune worth of - have things called morse tapers for the various tool bits. Morse tapers are adapters that allow you to quickly switch bits, most of the tooling that fits them is in Imperial. Collets, the elements that hold tooling for a mill or a lathe are all in imperial sizes. Unless you order from a very large catalogue it is very difficult to get mills in metric, but that is much more frustrating is that it can even be hard to source drills in metric.

Machining is done to thousands of an inch in the US. The rest of the world uses 1/100th of a mm for both turning and milling, and a series of fittings for more precise work.

The good news is that the bigger bearing companies all do carry metric if you need it. And if they don't have it in stock it 's usually only a day away.

Unless you've actually tried to design a somewhat complex chunk of machinery you might be given the impression that 'metric is easy'. In practice stuff like shafts, gears, supports and so on are all easier to source in Imperial than in Metric both in the US and in Canada too.

You want to order in Imperial, just one moment while I get your order form the warehouse out back. You want to order in Metric. That's perfectly fine, we're a metric country after all. Would it suit you to pick your order up in early march, possibly the middle of april before it is complete?

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)

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.

> Yes, there is a section for metric in the hardware store. It's the bit at the back with about 1/2 the sizes missing and only the stuff that you don't need in stock.

So, would your proposed law to switch the USA to the metric system require hardware stores to stock every size and always have what you need in stock?

This is a bunch of fictions. Americans with wrenches tend to have both SAE and metric sizes. The thread pitches of metric bolts differs from SAE standards, and drain pipes are sized on inside diameter not outside because ID is relevant to capacity.

Tape measures have standard units because they're standard where tape measures are used - in construction.

Where it makes sense, metric is common, e.g. soft drink bottles.

> This is a bunch of fictions.

Not really, those are all pretty practical examples. I've dealt with each and every one of those.

> Americans with wrenches tend to have both SAE and metric sizes.

The metric ones will be brand new if they have them, the imperial ones will be well worn.

> The thread pitches of metric bolts differs from SAE standards

Indeed they do. In the EU Ford vehicles are all metric unless they were private imports from the USA. I'm not sure what the situation is today but when I still lived in Canada the ford we had had all imperial sizes bolts as far as they were exposed.

> Tape measures have standard units because they're standard where tape measures are used - in construction.

Yes, and as long as you don't change that that's they way it will stay. The English drive on the left because they do. But that doesn't mean they can say that they've adopted driving on the right side of the road because they could. They haven't. So construction is almost entirely in Imperial.

In a metric country, metric is used everywhere, because it makes sense.

The U.S. auto-industry typically uses metric fasteners. In my experience, that's pretty much been the case since the early 1980's - though that experience is mainly with GM products.

Some of my older metric tools predate that. I owned a '64 Baja bug - thereby learning the art of static timing adjustment.

Changing tape measures isn't going to change US construction practice. Lumber has to change. Cold formed steel manufacturing standards have to change. Steel mills have to change.

All the engineering tables have to change. And insurance underwriters have to be willing to eat claims based on any confusion which this creates - it's kind of like the Hubble telescope without NASA redundancy, except that people will probably die.

The baja bug is a VW beetle re-run (so German, hence metric).

Agreed with all the other points and that is exactly why I think this will not happen.

I used to work as a professional mechanic and the auto industry used to be split, with American brands using SAE and imports using metric. This was all changing fast in the 90s such that pretty much everything is metric on cars these days. Still, there are a few exceptions here and there.

Two liter bottles are an anomaly. Every other pop container is in ounces. Cans are 16 ounces and bottles are usually 20 ounces.

I can't think of a situation where "metric is common" for consumer items.

California wine 750mL bottles. Obviously the imported stuff is in mL but so are the domestics.

Every OTC pharmaceutical I've ever seen, pretty much.

There's a pretty weird combination of liters and ounces in soft drinks. 2 L and 20 oz are very (most?) common for bottled soda. 1 gal is common for bottled water, but for individual bottles, 0.5 L (16.9 oz) is common. 1 L and 1.5 L bottles of various beverages are not unheard of. Cans of soda are generally 12 oz, though 16 oz and 24 oz are not uncommon among beers. Wine, as mentioned below, is often 750 mL, but liquor is often sold by the quart.

So I wouldn't say the 2 L bottle is the sole anomaly, but metric is definitely not the prevalent system for beverages.

Does anyone else on HN work on their own car? My ancient unbreakable domestic mfgr '97 GM car is all metric. Right off the top of my head the oil drain plug is a M12-1.75 bolt. I just replaced the battery two weeks ago, all metric (I think they were M10 bolts? I was in a huge hurry). Seemingly everything on my GM car is metric, and it was built 15 years ago, I can only imagine how metric everything in auto-land is now.

GM and Ford use metric for the last 20 years - but on a lot of their 'easily accessible' bolts, the heads are sized just enough to work with standard hobby imperial sockets. If I remember - That M10 will fit a 3/8" socket too, and M13 is used all over the place and will work with 1/2" socket.

On my wife's Suzuki their M10 will not work with a 3/8" socket, and if you get into anywhere serious on a GM or Ford - those bolt heads will be exact metric with no room for imperial.

That would make good sense. What about things like wheel nuts, hitch attachements and so on?

The ford I had had a surprising amount of imperial on it about a decade ago. Presumably under the hood and inside the engine it was all metric though.

I daily-drive a 1997 Ford Ranger pickup. The engine was produced in Cologne, Germany, and thus everything under the hood is metric. The body & chassis was built in Dearborn, Michigan, and thus everything not under the hood is SAE.

That perfectly matches my Ford experience.

"What about things like wheel nuts"

I can verify its 30 mm with my wheels/hubs on my car. Supposedly that's "unusual" and most cars that size are 28mm or 32mm so people end up mystified why their 28 doesn't fit something that looks visually at a distance like a 28, or they use a way too big 32 and neatly round off the corners of the nut when it slips. I imagine using an imperial impact wrench is an effective way to round off the wheel nuts on a Saturn.

I would imagine if you bought aftermarket wheels/studs alloy or steel you could have most any size within a narrow range that's compatible with the hub.

"hitch"

LOL at the idea of my tiny little 2-door subcompact towing anything like those giant RV trailers. I do know standard american trailer hitch on pickup trucks has been 2 inch square for a century or something like that. Kind of like how we're not going to change every piece of railroad track and rolling stock in the USA to a metric equivalent rail gauge any time soon, until the end of time we'll be stuck with 50.8mm trailer hitches. I bet you could slam a european 50mm in the hole within manufacturing/rust tolerances.

32mm is used all over in GM world - 32 just happens to be barely smaller that 1 1/4" inches so it keeps people that only have SAE sockets happy. 1

Completely depends on the car. Wife has a 2006 Mariner, it has 19mm wheel nuts. My '91 Explorer is 5/8" or 9/16" or so (I don't remember). I also have a BMW that's 100% metric of course. And a '68 mustang that's 100% SAE.

The explorer is metric in a lot of places. The engine is SAE since it's based on the 302 which was originally designed in the early '60s. Pretty much anything that was designed from the mid 80s or later will be 100% metric hardware unless it needs to work with something that isn't. And even then it'll will sometimes be metric until it hits the non-metric piece. For example, the Tremec T-5 transmission is metric but mates up to the Ford 302 which is SAE.

So basically, it's usually metric except when it's not.

Some of your examples are good, but many aren't based in reality for the US consumer. A lot of consumer goods are manufactured overseas, then imported to the US. The manufacturers of these goods rarely create custom versions that rely on inch-based hardware. The ISO nomenclature isn't very common, but 16mm wrenches are very common. Pretty much any US resident who wants to work on their car or assemble products without using the supplied stamped wrenches has to have both imperial and and metric tools. I've got a whole tool chest full of that mix in wrenches, sockets, and hex drivers.

When it comes to highways and tape measures, you're right though. A tape measure is most commonly used in carpentry, which is almost entirely imperial. Our cars all have speedometers that display MPH in large type, so I don't see that changing without some mandate.

The comment you replied to never claimed that the U.S. uses metric units, only that it has been legal and even encouraged since 1866. So to re-iterate, there no change needed to the law, it already allows metric just fine (as you yourself note when you mention that the government-run military understands metric).

Simply deprecating customary units won't be enough to make the switch, you would actually have to make it illegal, and Hell will freeze over before you'll see that pass in the U.S. ("Doesn't Congress have actual problems to fix???")

Actual problems like the dollar is no longer a defined weight of silver. Talk about weights and measures...

Where's the problem with that? You can price your goods in gramms of silver, if you like to. (You may have to quote dollar prices, but just adjust them daily based on the silver spot market prices.)

I worked in oilfield and petrochemical construction and manufacturing for almost ten years, and I can say that we almost never used metric. I think in the ten years, I worked on two projects that required metric bolts and fittings, both of which were for Japanese companies. Retraining the workers to use metric for these projects was a battle in itself.

We built structures and equipment that went around the world... all using imperial.

This is anecdotal, but I recall that Alabama put up highway markers in kilometers during the 1990's [1]. It confused people, and they cancelled the program. You can still find signs that haven't fallen down or been stolen in some places.

[1] http://lamar.colostate.edu/~hillger/signs/AL.html

I have all of those things except the drain pipe and a highway sign.

Every socket set i have contains both SAE and metric. Half of my power tools are in metric (festool).

All plywood that you buy from the hardware store in the US is really metric sized nowadays.

Every screw/fastener on every tool I own is metric or metric sized. I haven't used my SAE hex keys in eons.

When you say 'metric sized' do you mean 1250x2500 or do you mean 1219.20 x 2438.4?

Home Depot does not agree with you.

From http://www.homedepot.com/h_d1/N-5yc1vZbu0m/h_d2/Navigation?c...

this is my absolute favorite: "5.2 mm x 2 ft. x 4 ft. Sanded project panel", all the rest is in Imperial.

I mean that nominal 1/2" plywood is not 1/2" anymore, it's undersized to 12mm.

The width/length is not in metric, the actual thickness is, though they come up with an imperial equivalent that is within a few thousandths.

In other words, they tell folks 1/4 plywood is 15/64, 1/2" plywood is 15/32, etc. In reality, they are undersized to the nearest mm.

Like jaquesm says, I just bought plywood at home depot and it came in 6.45mm thickness, 24"x48". I don't know how you get 6.45mm either in metric or imperial, but it's clearly not "sized in metric".

Thickness wise, they are sized in metric. If you got 6.45mm, someone messed up :)

No non-hardwood plywood, even 1/4" plywood, is oversized, and 6.45mm would be oversized at .2539 inches. If it was actual 1/4" (hardwood plywood), it would be 6.4mm per APA (american plywood association) standards.

Outside of hardwood plywood, thicknesses are really done in metric.

1/4" nominal plywood nowadays is sized at "15/64" imperial, or in reality, 6mm.

1/2" nominal plywood is 12mm, or "15/32".

(the actual sizes are metric, but are close enough in tolerance to imperial /32 or /64 sizes that they work)

The only plywood you will find that is "actual" size in imperial is domestically produced hardwood plywood.

This is not a large percentage of produced plywood :)

>The only plywood you will find that is "actual" size...

Actual thickness you mean...

All construction sheet goods available in the US come in 4x8 sheets (drywall excepted, which I believe can be as long as 12').

Just because you can express "4ft by 8ft" as "Xmm by Ymm" (and that very well may be the official spec) doesn't make it 'metric' lumber in any meaninful way.

Actually, not all construction sheet goods come in 4x8 sheets, you have things like cement boards, which are 3x5 sheets. Same with some fiber based sheathings, some fire-code panels, etc. There are actually plenty of non-4x8 construction sheet goods.

In any case, let me make this very simple:

All non-domestically produced (and most domestically produced) sheet goods are produced to metric sizes that are close to 4ft x 8ft x whatever thickness. They are whole number integer metric sizes. They are metric sheet goods. They are produced and measured metrically by every producer and exporter.

They get sold as imperial sizes in the US. However, the fact that they are close to some imperial size does not make them imperial sized lumber in any meaningful way.

If i take a bunch of things that were produced as squares, sell them as circles, and people keep calling them circles, that doesn't make them circles.

You can call a 4ft x 8ft x 1/2" piece of sheathing 4ft x 8ft x 1/2" if you like. But it's neither 4ft, nor 8ft, nor 1/2".

If you don't believe that sheet goods produced and measured metrically to whole number metric sizes are metric sized simply because someone in the US decides to call it something different, we'll have to simply agree to disagree as to whether they are metric.

I'm happy to agree that folks in the US don't work with the metric system intentionally, but they are working with it, whether they know it or not.

This whole discussion started because one of the premises given was that things like construction sheet goods (and lumber, but let's stay simple) would have to change for folks to be able to use the metric system in the US.

As i've shown, this is simply false, they just need to pretending they are imperial sizes, because the construction sheet goods are already done to metric sizes.

0.003" could easily be thermal expansion or humidity.

relevant onion article: http://www.theonion.com/articles/metric-system-thriving-in-n...

I live in a metric country so I agree with everything you say, though a metric only tape measure is possibly less important. Actually I have two tape measures handy, one is metric only and the other has metric and imperial units. I think you'd expect to see both units for quite some time after conversion. Interestingly the one that is metric only is a style that tradesmen often have. I gather if you are measuring things all the time, you'd only want to deal with one set of units. So perhaps the option of having a metric only tape measure is still useful.

I like in the US and am from EU. As a result, while I try to ask for things in imperial units, I happen to ask for tools and related things in metrics from time to time. My experience is as follow:

- most people actually just get me exactly what I want

- nobody ever complained "why do you ask metrics, you're in the US we use imperial!!", ever

- nobody ever told me "I don't know what that makes in inches, do you know it in inches?" (or similar), ever

So while I'm just one person and all, I still have a feeling this could eventually work.

This is true. However, this is not insurmountable:

http://xkcd.com/526/

The key is, I think, start with the measurements you use in your daily life and start estimating in those terms. Use it in the office. It might be accelerated if there's a metrics app for the Google Glasses, automatically converting signs into metric. You start saying, "dude, that bouncer must be two meters tall!" and getting everyone around you to convert.

Oddly enough, highway signs in km can be found for about 20km north of the border town of Nogales, Arizona.

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