Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx> At 05:47 PM 1/18/2006, Tesla list wrote:
Original poster: Steve Conner <steve@xxxxxxxxxxxx>who write that something was built out of "lumber 5.08 x 10.16 cm" instead of "2x4's"I've seen a lot of stuff like this as the UK gradually gets more and more metricated :-) I remember an advert for one piece of software that came on a "89mm" floppy disk. Which is just plain stupid, as you have to get out your calculator to figure out that it's a 3 1/2" disk. Another crazy thing I saw recently was architect's plans for a multi-storey building with all the dimensions in millimetres.
Oddly, I worked on some special effects equipment for a roller coaster. The coaster was designed (and partly constructed) in Japan, so the drawings were all in millimeters. We had a chuckle at BIG things (like 20 meter long sections of track) being specified to the tenth of a mm. However, when the pieces were delivered in installed, darned if they hadn't held the tolerances. You've got to choose some base unit to work in, and you could either choose meters or mm, I guess, and with mm, you only have one decimal place to worry about. Lots of stuff is a few cm in size, and all those: hole diameter 0.0127 meters specs gets tedious.
It's a LOT better than feet, inches, and fractions! Even surveyors use decimal feet.
Probably the worst thing is printed circuit boards. These were traditionally done in grids that are sub-multiples of 0.1 inch: 1/10", 1/20", 1/40", 1/80", 1/160" etc. But most new component packages have metric pitches and when you mix the two types on one board (as you very often have to) the result is just a total pain in the ******Or the mounting screws on VME card cages (VME was developed in Germany, so all the dimensions are metric) that are 2.54 mm apart.
At least John Freau hasn't started selling 100 x 330mm spun toroids though. I don't know why, but I always end up building my Tesla coil equipment to inch dimensions. Having said that, my idea of precision engineering is "I think I'll drill a hole hereabouts" so you probably couldn't tell if it was meant to be metric or imperial in the first place.