The Metric System

Great video.

How about using metric horsepower [Pferdestärke (PS)]. instead of Watts and go all JDM? 280PS makes more sense than 206kW.

Another thing-

Before anyone starts to talk about how Canada did it with minimal opposition and other nations did it well… we need to remember that the US is the 3rd most populous nation on earth. China has 1.36 billion, India has 1.25 billion, and then the US has 322 million. That alone makes for a logistical nightmare. Canada currently has 35 million people, and they had about 21.3 million at the time of the change. It is going to take fewer resources to acclimate 21.3 million people to a new standard than it would 322 million.

[quote=”Evil-i” post=146230]I suspect that if the US ever does adopt metrification, the results would be similar. You’d have a society that is ostensibly metric, but a lot of real-world activity would continue under Imperial measurement.[/quote]

I almost exclusively use the metric system at work for distance, mass, temperature, volume, etc. However, I “live” in an Imperial world. if the US suddenly converted to metric, I would be disoriented when weather is reported in Celsius, driving consists of km, km/hr, km/L, etc. It’s probably that I’m accustomed to a unit system and range of normal values for certain things, although I despise the quick-math needed for fractional inches and drill sizes.

There was a Mars spacecraft that was lost because some calculation was performed with Imperial units, and the error propagated in the rest of guidance software. So, even the aerospace guys have bad days.

Giving some British perspective here, we actually use a hybrid system similar to Canada’s. Distances are still given on road signs as miles, not kms, and car speedos typically have both MPH and KM/H scales with the MPH numbers being larger.

Weights and measures (including fasteners on vehicles) are typically all metric, although older people tend to prefer using imperial for weights – pounds and ounces instead of kilos and grams. And the construction industry still talks of “two by fours”, even though the actual measurements are done in metric.

As far as fasteners go, metric makes total sense to me, whereas SAE makes no sense at all (because I’ve never learned it and I see no reason to start now). I work on two Jeeps, one from 1992 and the other from 2005, and 99.9% of the time I only use metric sockets. I think I have about three SAE sockets for specific fasteners where the closest metric equivalent either doesn’t quite fit or might run a risk of rounding, and I rarely ever need to touch those particular fasteners anyway.

Seriously, I just don’t understand why anybody would prefer an ascending sequence of fastener size going 5/16, 3/8, 7/16, 1/2, 9/16, 5/8 when you could have 8, 9, 10, 11, 12, 13, 14, 15, 16. SAE isn’t intuitive and the relationships have to be learned, whereas the typical three-year-old knows enough about counting to have basically mastered metric.

Yes, of course people are used to what they’re used to, but sometimes change is necessary and useful. In the UK in 1971 we switched from our old imperial currency system (which had existed since Roman times) to decimal. It was a massive change and cost money to do, and there was considerable resistance from a large chunk of the voting population, but the old system was extremely confusing to anybody coming from a country with a decimal currency – which was just about every other country in the world. It was an antiquated relic and needed to change.

To anyone born in the UK after decimalisation (which includes me, by just a couple of months), the pre-decimal currency system seems ridiculously complicated – it used units with two different ratios, one at 12:1 and the other at 20:1 – but ask anyone old enough to have worked with it every day, and it makes perfect sense. I guess like SAE fractional sizes do to American mechanics 🙂

Biggest problem with Metric fastners is there are 5 thread pitches vs 2 thread pitches with SAE fastners.Another thing with metric is most socket and wrench sets leave out 18mm and sometimes 15mm making the set worthless.

[quote=”wafrederick” post=146371]Another thing with metric is most socket and wrench sets leave out 18mm and sometimes 15mm making the set worthless.[/quote]

“Worthless” would mean it’s no good for anything at all, which is clearly not the case. When I first started I made a point of buying a socket set that included everything from 8mm up to 23mm, but for a good 90% of the jobs I do I only need 10, 11, 12 and 13 – so a basic set would work just fine. In any event, surely it’s up to the buyer to check what’s in the set and if any sizes are missing – in my experience, 16mm is the size most commonly missed out in DIY-level sets – to buy them separately. Every tool shop I’ve ever been to has sold individual sockets as well as sets, and they’re hardly expensive.

[quote=”ToyotaKarl”]I like the metric system much better, but must admit I will have a hard time letting go of Ft-lbs and Horsepower….[/quote]

Well, we haven’t had to do that here in the UK!

As I mentioned earlier, even though we’re an officially metric country, many things are still expressed in imperial units. Official documentation for cars usually quotes PS, but in the real world people still talk in horsepower. We still use miles for road distances. I prefer Nm to ft-lbs, simply because my three torque wrenches are all Nm and it’s a pain having to convert, although fortunately the torque specs in both my factory service manuals for my Jeeps give both Nm and ft-lbs for almost every case.

Even if the USA doesn’t formally switch to metric, it’ll probably end up with a situation much like the UK (or Canada) – over time, vehicle fasteners will become metric as standard and people will just find themselves using metric tools.

Some of the issues raised here are in my opinion somewhat red herrings, e.g. the road signs. Road signs can be ‘retrofitted’ with stick on markings, look for any road sign where someone might have made a mistake or has been updated without being replaced. We had an old 30 mph sign that had a ‘5’ stuck over the ‘3’ and a ‘km/h’ stuck on the bottom. It would have been modified in the 1970s, and looked quite unusual when it was removed a few weeks ago.

Tell your tool set manufacturers to stop being cheap and assuming that everyone already has an imperial set of tools and supply all the metric sizes.

There are multiple metric threads, but unless you’re using them for a specialised application the ‘coarse’ threads are the ones that are always used. And if you’re wondering how to work out what hole size to use for tapping a thread for a metric bolt – just subtract the thread pitch from the nominal bolt diameter. So for an M10x1.5mm bolt, use an 8.5mm drill. That’s it.