Inches or millimetres ?

I'm mugging up on military standards for a job interview next week and was intrigued to find that all the US MIL STDs I downloaded now use metric exclusively, and have 'Metric' written on the front page.

Leon

Virtually every machine shop I service machines in, still uses inches, not metric. Even when cutting to metric dimensions. They simply convert to decimal inches.

Southern California.

Gunner

"To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas

Sheet metal and printed circuit board work are both done in inches with a decimal fraction. The printed circuit board software often needs to handle components on metric centers. It can be a pain getting things back and forth from the inch grid to the metric grid.

Wire and cable, inches and fractions on the assembly drawing, inches and decimal fractions in the inventory software.

Machine work, test fixtures etc, inches with decimal fraction.

Circuit noise calculations, sensor calibration, color temperature, degress kelvin. Environmental testing, degrees centigrade. The one non-metric scale I'd be pleased to do away with is temperature.

Some screw terminals and laptop style hard drives and cd-rom players are metric.

Well here in Canada we are suppose to be using the Metric system. I'm 39 years old and halfway through school started learning metric. Now it seems like I'm a mixture of the two systems. Linear measurement I use imperial but when I think driving speed and distance I mentally think in metric. Like if I'm going to Windsor from my house Its slightly more than 100 kms and since I'll be driving 110-120 kms/hour Its easy to figure the trip will take an hour. But when I think about temperature I use farenheit. Celcius seems like to small a scale. A 1 or 2 degree change in farenheit is no big deal but in celcius the difference is quite large.

Of course industrial here doesn't seem to quick to change. Our company is running a specail right now on metric/imperial tape measures and sales is slow cause one side of the tpae is useless to use cause it got all though weird metric markings on it. Seems like it'll take years and years and years to change over.

Metric at work, inches at home on my hobby machines. We changed over at work in 1978. Lots of fun for a few months, sitting around with a calculator converting measurements. I still have .03937 embedded in what little brain I have left. After a lot of calculation errors, management sprung for new dro's. That pretty much took care of the manual machines. Sitting at a bench converting measurements on a complicated print isn't how to get anything done.

Lets face it, whats the difference? Inches are bigger than mm. Decimal inches and decimal mm are handled in exactly the same way. The biggest arguement is fractions. Metric rarely uses them. Other than that it's all down to what we are familiar with. People can imagine a man who is 6 ft tall because they are used to that. We (UK) used to be imperial. we even had strange money called shillings and pence. That was really cruel but some folks missed it when we went metric. Could you Americans manage with 20 bigthings to the dollar and 12 littlethings per bigthing? Your money is metric, so are the number of your fingers and the design of your numbers. All we have to do is get used to the units. The base 10 system works far better.

John

Canada was mandated to be completely metric by 1980. It didn't happen. I use both systems when fabricating steel work. Metric is by far less error prone. So far in Canada fasteners for structural are still inch threads. A proper metric tape is hard to come by. The most confusing thing about metric is people wanting to use centimetres and metres. I quickly learned from the European tradesmen that you stuck with millimetres even if the thing was 20,000 long. The final argument I have for metric is that the majority of the world uses metric. There are only a few countries holding out. I have lost count of the number of jobs that have been screwed up by someone deciding that they will convert the drawings or material lists to inches and feet. Use one system or the other. Don't start mixing things up.

Randy

The fact that Metric is a base 10 system doesn't make a great deal of sense in the computer world. Fractions are a lot easier to use in inches than in metric simply because we tend to use a de facto binary methods with them. In other words, it's easier to think in absolute terms with fractions than discrete units. You'd think that the metric system could have anticipated this, but the introduction was too early in relation to the timing of widespread personal use of the device. A shame. Eighth of a millimeter anyone?

One of the early problems, way back when US tried to switch, was with the machines. Before DRO, when you only used the hand wheels on a lathe or mill, they were in inches. So you had to convert all dims on the paper drawing, or buy a new machine with metric dials. So most of us had to use both metric and inches at the same time. But I guess the one you learned first or grew up with will be dominant.

The meter was defined in 1889 ... so long before the russian revolution!

Gunner wrote

That's the way it is, and its an expensive exercise to convert machines or buy replacements. Easy options - move manufacturing to Asia where they have already got metric machines. Happened in Australia and its happening in the USA as we speak.

Globalisation - metrification - free trade, all terms meaning screw the worker, profits are all that matter to these guys and they'll tell you all sorts of stories to hide the real agenda. The agenda - employ the guy for the least cost. Thatcher and Reagan are not heros!

Glenn

I'm American and proud of it! Going metric is the same as bending down and kissing Europe's feet. I felt the very same way when the idiots in our military adopted the 9mm as an official service round. I'll take a .45ACP anyday!

I'd rather it be Soviet/Russian, unfortunately metric is a French contrivance.

F the Frenchies, Triumph the Insult Dog my hero!

[ ... ]

Hmm ... I work in both -- whatever fits the need. (And I keep a calculator handy. :-)

But when I want to do relatively precise work on my little Compact-5/CNC, I will convert everything to metric, because the smallest step size in inches is 0.001", while metric has the smallest step size at 0.01mm (which is 0.000394").

In particular, diameters are specified in those units, but because it is really the radial motion which is controlled, not the direct diameter, you have to specify diameters in steps of 0.002", or

0.02mm -- so working in metric lets me specify to slightly smaller than 0.001", while I am stuck with 0.002" in inch mode. (I can't switch back and forth within a single program.) There is a switch on the front panel, which defines all units and programs to be inch or metric, with no switching in the middle. (And higher resolution is not available, as the leadscrews are driven by stepper motors and full-step controllers.) (Well ... I could replace with higher resolution steppers, or with servo motors and encoders -- but then I would also have to replace the controller, as there are not enough digits to handle finer units.

On the Clausing, however, I normally work to inch dimensions, as the dials are all calibrated in inch units. (Though I can (and do, from time to time) turn to a metric diameter on the inch machine. Threads are another kettle of fish, however. I do have the metric gear set, including the alternate spider that it requires, but I normally take anything which requires metric threads to the Compact-5/CNC, where the y are trivial.

Enjoy, DoN.

Quite so too. But he wasn't concerned with details like that. For instance, because of the war he steadfastly refused to buy anything Japanese if he could possibly avoid it. Looking back now, I admire him for those things even though at the time I thought he was just a stubborn old mule. He had a good argument for the superiority of Imperial measurements over Metric. He said " Look, you go one inch then half an inch then a quarter then an eighth then a sixteenth etc etc. Each time you double your resolution until it is sufficent for the precision required. " I still think this argument has merits.

Dean.

It's a pity the GM cars I work on now require me to have metric tools.

Oh well.

I got new sockets and wrenches and got of it.

Nuf said.

I too am an American, more explicitly a U.S. citizen. And I am proud of it too. But don't think that using English units and kissing Englands feet is better than using metric and kissing Europes feet. Besides I was an Electrical Engineer and all the electric stuff is metric. Kilovolts, gigahertz.

IIRC the U.S. has officially been on the metric standard since before I was born.

Dan

On Fri, 20 Feb 2004 15:09:32 +0800, "Dean" vaguely proposed a theory ......and in reply I say!:

I don't reckon your grandma is being any less sensible than the tube and pipe makers are now with their "metric" sizing. I have had people on metal and irrigation shops quite blandly tell me that 40mm is 1.5", or 30mm is 1", and even further off than that.

Also, in the cases where they decided to keep the dies, you _do_ have to ask for 25.4mm.

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.........no I'm not! remove ns from my header address to reply via email

Spike....Spike? Hello?

Right. Having a base where integer division is simple and intuitive does help. Base 2 is simplest, but having a base with several integer factors, such as base 12, base 16, base 36, or base 60 also has great advantages. Base 10 is actually sort of lame.

There's good reason why decimal hours never caught on. There's also excellent reason why grads never replaced degrees for angular measurement. Base 10 units just don't fit well with ordinary notions of time or angular displacement.

Gary