Milimeters

[Brett Buck]

I think it depends on what supplier you use and how detail oriented they are. When I order 1/16-inch sheeting, I expect to get just that. My supplier sells only wholesale to the trade, and you'd think they might not be so detail conscious. I'll keep a close check on the next order - that's due in tomorrow - to see if the tolerance holds.

Most of the cutters have just one sander. They have to readjust it to each size balsa they run. You would think that they'd have presets on the dials for each size once they hit it perfect, but I suspect that, due to the density variations in balsa, it doesn't work that way...

Bob Hunt

  I am amazed they can do it at all, and the waste has to be astronomical. Half or more of the wood goes in the exhaust duct, so it's no surprise it's expensive.

   Brett

[Randy Cuberly]

I'm going to tell you the real answer but the censer may not allow me to say it.
Like the english language the us standard of measurment is a bastardized system.
Here we have inches,feet and yards and when we come to doing fine measurments we throw away the standard measurments and go to thousandths of  and inch. Which means the standard ruler is useless.
So we should have scrapped it years ago.
And embraced the metric system. where everything is 1,10,100, or 1000 th os a centimeter.
centimeter,milimeterm or meter. all being variations of the same thing.
But one must learn it without being give another standard to confuse the issue.
The big problem being that we all hate change. even change for the better.

The real problem with converting to the metric system in the US was simple economics.
At the time the conversion started all of the available machinery in the US ie. lathes, milling machines, drills, grinders, etc. were manufactured and graduated in inches.
Conversions were necessary between the design drawings and the machinery (machinists).

At first this was accomplished by having dual dimensioned drawings, dimensions given in both metric and inches, then by just placing a metric conversion chart on the drawing dimensioned in inches...what an incredible mess that created.  As changes were made to drawings conversions were often overlooked and viola...big errors, sometimes on hundreds or even thousands of parts before the error was caught.
Threads were a real problem because most lathes used gears  to drive thread lead functions and the conversions were often not exact and long leads lead to errors.
Thousands of parts especially screws were stocked by industry and the military...so we wound up needing two separate stocking facilities...I don't have to tell you what happens when someone orders 20,000 .250-20 screws but recieves 20,000 6mm screws instead.  They look very similar but of course won't interchange.

Some of these problems actually shut down automotive assembly lines for months not to mention huge costly delays in the aerospace industry.
Some manufacturing experts actually list this as one of many reasons the US manufacturing industry began to fall behind the rest of the world.

Finally after many years of expense and quality nightmares the decision was made to scrap the metric system conversion for most manufacturing processes here in the US.
The automotive industry still has problems with mixed hardware etc. on currently manufactured cars.

Metric nightmare...

Yes the metric system is simpler, better, and more useful but not worth the effort of conversion.

Of course the problem was much more complex than this simple discussion can explain but it does cover the biggest problems.

Randy Cuberly

[David Russum]

I weigh my planes in troy ounces - they come out lighter that way.....

What always gets me is how the metric system is used rather than the difference in units.  For example, the speed of a car or airplane will be in km/h, but wind speed is measured in m/s.   Why???  Seems to me that it would be easier to comprehend wind velocity in terms of the speed of a car or a bicycle or whatever you are more familiar with, especially with airplanes where you may be directly comparing the wind speed to the speed of the airplane. Then there is this l/100km measurement for fuel economy.  Huh???  Unit of fuel divided by some arbitrary distance rather than unit distance divided by unit of fuel....being contrary just to be contrary?  I don't get it....

While the metric system is good for converting between mass, volume, size, etc., in real life I find that I really don't need to do those calculations that often, so I will stick with the more "human" sized measurements of the English system.

[Steve Helmick]

Back when there was a movement toward the metric system here in USA, I was told by my leadman at Boeing that the English metric threads were 55 deg. form, while everything else was 60 deg., and USA, German and Japanese metric threads were all different in various details, such as root flats or radius and peak flats or radius. Totally makes no sense at all.  Steve 

[Randy Cuberly]

Back when there was a movement toward the metric system here in USA, I was told by my leadman at Boeing that the English metric threads were 55 deg. form, while everything else was 60 deg., and USA, German and Japanese metric threads were all different in various details, such as root flats or radius and peak flats or radius. Totally makes no sense at all.  Steve 

Yes Steve, but that was all before the ISO metric system was adopted by all of those countries mentioned.  The ISO system is standard world wide.

BUT...not everyone uses it.

[Steve Helmick]

Yes Steve, but that was all before the ISO metric system was adopted by all of those countries mentioned.  The ISO system is standard world wide.

BUT...not everyone uses it.

Don't tell me...it's the French that don't use it?   Steve

[qaz049]

Back when there was a movement toward the metric system here in USA, I was told by my leadman at Boeing that the English metric threads were 55 deg. form, while everything else was 60 deg., and USA, German and Japanese metric threads were all different in various details, such as root flats or radius and peak flats or radius. Totally makes no sense at all.  Steve 

While it may be true that there were local minor variations in the characteristics of Metric threads, it's unlikely that the British Metric were 55 degrees.

The Whitworth threads were 55 Deg and that was IIRC the world's first standardized screw thread system, dating back to the beginnings of the Industrial Revolution.

Your friend may have been confusing the latter with the BA (British Associated) series which was used on scientific and electrical equipment, and amongst other things, model engines.

It was/is Metric and had a thread angle of 47.5 degrees. I was taught in College, that the US only really standardized their screw threads during WW2 with the Army/Navy screw series.

[Curare]

I'm going to tell you the real answer but the censer may not allow me to say it.
Like the english language the us standard of measurment is a bastardized system.
Here we have inches,feet and yards and when we come to doing fine measurments we throw away the standard measurments and go to thousandths of  and inch. Which means the standard ruler is useless.
So we should have scrapped it years ago.
And embraced the metric system. where everything is 1,10,100, or 1000 th os a centimeter.
centimeter,milimeterm or meter. all being variations of the same thing.
But one must learn it without being give another standard to confuse the issue.
The big problem being that we all hate change. even change for the better.

Yes, this is why I prefer metric over imperial. The only thing that is easily divisible (in my head) is thou, why? add or remove zeros to go from inches to thou.

With metric I can go from piccograms to tonnes, all by adding or removing zeros. I can go from nanometers to kilometers (or further) in the same way. This also fits in nicely with a lot of engineering terms, pascals, hertz,etc.

[James_Mynes]

Who would have thought 25 degrees was t-shirt weather?

[qaz049]

Who would have thought 25 degrees was t-shirt weather?

Ah those French!

The smartest and the most civilized nation on earth.

 

[PerttiMe]

Who would have thought 25 degrees was t-shirt weather?

"""
In short, 100 means nothing on the Fahrenheit scale, 96 used to mean something but doesn't anymore, and 0 is colder than it ever gets in Denmark. Brilliant. Lest we get too down on Fahrenheit, though, consider Anders Celsius, who devised the centigrade scale (0 to 100). Everybody agrees Celsius's scale makes more sense than Fahrenheit's. Trouble is, the original Celsius scale had 100 for freezing, 0 for boiling. In other words, it was upside down. (The numbers were reversed after Celsius's death.) You have to wonder whether these guys breathed one lungful of mercury fumes too many.
"""
http://www.straightdope.com/columns/read/1266/on-the-fahrenheit-scale-do-0-and-100-have-any-special-significance

[pipemakermike]

One thing not often mentioned is that 12 is a much more useful number as it has so many factors - it can be devided by 2, 3, 4, 6, where as 10 can only be devided by 2 & 5
I was born in imperial measures but have worked all my life in both so am equally at home in either or a mix of both

Why haven't they decimalised time? Is is because 60 has so many factors - 30, 20, 15, 12, 10, 6, 4, 3 & 2

[PerttiMe]

Why haven't they decimalised time? Is is because 60 has so many factors - 30, 20, 15, 12, 10, 6, 4, 3 & 2

The French tried it 1793 to 1805, to remove all religious and royalist influences from the calendar.
http://en.wikipedia.org/wiki/French_Republican_Calendar

To make a year add up, they had 5 or 6 days that fell outside the "months".