John - I think there is only one metric system (ISO), but as you say I have found there are five different thread forms on 12mm nuts and bolts. The bulk of metric threads I come across seem to be 7mm; try to buy some they are an odd size. “We will have to specially import them so they will cost four times as much as an 8mm” is the normal response. The UK going metric just threw another joker into the pack. The Victorians were supposed to have standardised threads using British Standard Whitworth and British Standard Fine, but that did not stop industries adopting their own thread forms, gas, water, cycle, electrical, pipe, leather etc., and then companies within these industries using different thread forms, Lucas for instance. In WW11 the nuts were made smaller to save steel so a 7/16 inch spanner (wrench) was needed for a 1/2inch nut, just to add to the confusion. Then they had the bright idea of standardising everything using UNF and UNC which was completely compatible with the American system. As soon as this was up and running they went metric, this just made the system worse; stick with SAE. These threads don’t just disappear they are all still kicking around; I have a classic car with UNF threads, when I was at work they were still using BSW and BSF.

 

Ahh the Whitworth thread, a great idea that lost out to the convenience, not superiority of 60°. It is still used for fine threads that will hold, I am told.

Anyway, what I don't like about the metric system for everyday use is that the units are either too big or too small, including their names. It is as if it were designed by a bunch of academics who had never put air into a flat tire. Centimeter and decimeter are a mouthful compared to inch and foot. Centimeters are just too darn small for everyday life. A mil is a nice measurement for reasonably precise work; a millimeter is too big and a micron is way too small. Etc.

Anyway, after GM converted to metric, it went bankrupt.

John

 

I wish the UK would fully move over to metric, for example all road signs are in miles, but petrol is sold by the litre and fuel efficiency is usually quoted in miles per gallon.

It's worse in Ireland, the speed limits are in km/h and some signs have distances in miles, some in km.

 

I'd say that's better not worse Mark. I've never seen anything publicly here in the US that uses the metric system. If you have mixed systems you can at least 'grow up' with the mental comparison.

 

Is that right? I always use a nanometer as being ~5 picofurlongs. If what you say is so, then things are really going to be different from now on.

That assumption is why the mars orbiter crashed. It's a common mistake.

 

Where did I go wrong? (attached)

 

Where did I go wrong? (attached)

It was my mistake I was trying to make light of.

You have: 1 nm
You want: picofurlong
* 4.9709695

That's with the 'units' command on Debian, my first answer was from my hexadecimal slide rule.

 

And here I thought we evolved from something without feet. If more got turned up for our feet, then we would have to be shorter, right?

Which metric system do you think we should be on? Last time I checked, there were 5 different metric standards for nuts and bolts, but only one SAE standard. My rulers have measured in tenths, hundredths, and thousandths for as long as I can remember.

BTW, I didn't know "warp" was a metric measure of speed? What exactly is warp 8?

John

Warp 8 is C(speed of light) to the 8th power. According to the Star Trek dictionary. Yeah there is one, and a Klingon vocabulary primer too. They got way to much time on their hands, and I got too much for even knowing they exist.

 

Warp 8 is C(speed of light) to the 8th power. According to the Star Trek dictionary.

C^8 seems awfully fast. Gosh, you could make it across the whole galaxy in no time. It is just not right.

http://en.wikipedia.org/wiki/Warp_drive_(Star_Trek)

For warp 1–9, s(w) = w^\({10 \over 3}\)c. <snip>

Exact velocities were only given in the Voyager episode "The 37's" where Tom Paris describes Voyager's velocity at warp factor 9.9 (under the new warp table formula) as being about 4 billion miles per second, which would be over 21,000 times the speed of light.

As for Klingon, I read some interesting stories abut how it was developed as a real language before it was actually used in a script. A lot of shows have some pretty high-level thought behind them -- I am thinking of the Simpsons, not Desperate Housewives.

John

 

It was my mistake I was trying to make light of.
That's with the 'units' command on Debian, my first answer was from my hexadecimal slide rule.

Oh, misunderstood...

I know I'm often wrong --- "If it's true that we learn from our mistakes, then I must be learning a lot!" --- but my MathCad is usually not wrong nearly as often as I am.

Can you post a picture of that Hex slide rule?

This is a click and drag version that is very similar to my favorite.

http://www.antiquark.com/sliderule/sim/n4es/virtual-n4es.html