Metric vs imperial
08-20-2014, 11:29 AM
#4
I sent this to a few coworkers who think the metric system is too difficult to learn, and believe the imperial system is somehow easier. This is also a beautiful explanation; Metric 4 US - Why Metric is the Better System
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08-20-2014, 11:33 AM
#5
Boost Czar
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You dont need that site.
You need this:
9mm
or
0.354331in
10mm
or
0.393701in
or my favorite when I'm measuring
320cm
or
120 inches and like 15/16 or 31/32. no 121 inches minus one-half notch.
You need this:
9mm
or
0.354331in
10mm
or
0.393701in
or my favorite when I'm measuring
320cm
or
120 inches and like 15/16 or 31/32. no 121 inches minus one-half notch.
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08-20-2014, 12:36 PM
#6
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Makes logical sense:
inches, feet, and yards is easier to understand than milli/centi/- meter....hmmm nope, don't think so.
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08-20-2014, 07:55 PM
#14
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My grandfather the land surveyor used some system where feet were broken into tenths instead of inches. He always referred to it as "architects scale." This always boggled me as a child and made working with him to build things like fences and doghouses an impossibility. Years later I ran into this again while learning mechanical drafting, but then its still 12" in a foot, but each inch was divided into tenths...
Seriously, what the actual ****.
Seriously, what the actual ****.
Last edited by EO2K; 08-20-2014 at 08:17 PM.
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08-20-2014, 08:47 PM
#15
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Metric is far superior, especially when working with non-car/mechanical people. Going from 7/8 to 15/16 is not "one size bigger" is many peoples' mind. 'Course, a good mechanic can eyeball the size.
The nice thing about having two systems, is that when the metric rounds the edges off, you can hammer on an SAE.
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08-20-2014, 09:13 PM
#17
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Tyre sizes are f'ed up though: 225/45/15 = 225mm wide for a 15" rim.
Did they just want to annoy everyone when they came up with this standard naming convention?
Interesting sidenote: Australia went metric in the 70's yet even today we still often refer to people's height in feet and inches and when babies are born their weight is often mentioned in pounds. Strange how stuff like this persists.
Did they just want to annoy everyone when they came up with this standard naming convention?
Interesting sidenote: Australia went metric in the 70's yet even today we still often refer to people's height in feet and inches and when babies are born their weight is often mentioned in pounds. Strange how stuff like this persists.
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08-20-2014, 10:11 PM
#18
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In the US, the medical industry is 100% metric, except they give baby data in Lb-Oz and Inches. Guess it's about the target audience.
US cars are almost all metric now.
We work in "inches" at work, but all decimal inches, which is to say a metric system.
When we do work in metric, it is still decimal, as sometimes +/- 1mm is too coarse.
US cars are almost all metric now.
We work in "inches" at work, but all decimal inches, which is to say a metric system.
When we do work in metric, it is still decimal, as sometimes +/- 1mm is too coarse.
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08-20-2014, 11:34 PM
#19
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[rant]
The electronics manufacturing industry is a terrifying mishmash of standards.
Through-hole electronic components are all laid out on a grid measured in tenths of an inch.
The surface-mount devices which are replacing them are, for the most part, laid out in mm, though not always in even multiples of them.
Except for surface-mount resistors and capacitors. Those are measured in hundredths of an inch. So an 0805-package surface mount resistor, for instance, measures 0.08" x 0.05" in size. (Except that it doesn't, since the 0805 name is actually an approximation of the TRUE size, which is in fact metric. An 0805 part is really 0.079 in × 0.049 in, which turns out to be exactly 2.0 mm × 1.25 mm. Not that it matters, since the machines which place them aren't typically accurate to anywhere near 0.001". They don't need to be.)
The wires that connect it all together are (in the US) measured in AWG, which correlates to literally no other standard at all. Seriously, a wire's rating in AWG goes all the way back to the number of passes through some particular die set back in the 1800s that was required to draw the wire used to make cattle-fencing down to that size. A 16 AWG wire had to be drawn 16 times. (This is why the numbering system seems "backwards", with larger numbers representing smaller wires. The more times the wire is drawn through a die, the narrower and longer the wire gets.)
In Asia, wire gauge is helpfully expressed in mm^2. Which is nice, as the cross-sectional equivalent of PCB traces is also expressed in mm^2. Except that the thickness of the copper foil from which PCBs are manufactured is specified in ounces per square foot. In other words, 1 ounce of copper, rolled out to cover an area of 1 ft^2, gives you a copper-foil thickness of "1 ounce." (I can't make this **** up.)
The thickness of the PCBs themselves are specified in mils (thousands of an inch), but in increments which seem utterly bizarre until you release that they are imperialized approximations of metric approximations of 32nds of an inch. (I **** you not.) Why 32nds? Because this was how lumber yards specified the thickness of Bakelite laminate back in the 1940s when modern PCB technology was invented, and the first large-scale PCB fabricators simply ripped off the machines used to manufacture kitchen countertops.
The connectors used to make all these interconnects are a mishmash of different standards- some SAE, some metric, often both in the same part. Most of the newer stuff, blessedly, is all metric, even the American-made parts.
Except for large RF connectors. Those are typically specified in fractional inches, with a precision of 1/8". Except that these measurements don't actually refer to the size of the connector itself, but rather the "nominal" diameter of the equivalent copper plumbing pipe from which the first large-diameter RF hardlines were produced shortly after WWI. To this day, we still refer to heavy RF cabling as "plumbing," and in fact many of the same tools are used to assemble it.
It's a miracle that we manage to actually build anything that works. I'm still waiting for a datasheet which specifies mating pressure in something like nanosthènes / parsec^2.
[/rant]
The electronics manufacturing industry is a terrifying mishmash of standards.
Through-hole electronic components are all laid out on a grid measured in tenths of an inch.
The surface-mount devices which are replacing them are, for the most part, laid out in mm, though not always in even multiples of them.
Except for surface-mount resistors and capacitors. Those are measured in hundredths of an inch. So an 0805-package surface mount resistor, for instance, measures 0.08" x 0.05" in size. (Except that it doesn't, since the 0805 name is actually an approximation of the TRUE size, which is in fact metric. An 0805 part is really 0.079 in × 0.049 in, which turns out to be exactly 2.0 mm × 1.25 mm. Not that it matters, since the machines which place them aren't typically accurate to anywhere near 0.001". They don't need to be.)
The wires that connect it all together are (in the US) measured in AWG, which correlates to literally no other standard at all. Seriously, a wire's rating in AWG goes all the way back to the number of passes through some particular die set back in the 1800s that was required to draw the wire used to make cattle-fencing down to that size. A 16 AWG wire had to be drawn 16 times. (This is why the numbering system seems "backwards", with larger numbers representing smaller wires. The more times the wire is drawn through a die, the narrower and longer the wire gets.)
In Asia, wire gauge is helpfully expressed in mm^2. Which is nice, as the cross-sectional equivalent of PCB traces is also expressed in mm^2. Except that the thickness of the copper foil from which PCBs are manufactured is specified in ounces per square foot. In other words, 1 ounce of copper, rolled out to cover an area of 1 ft^2, gives you a copper-foil thickness of "1 ounce." (I can't make this **** up.)
The thickness of the PCBs themselves are specified in mils (thousands of an inch), but in increments which seem utterly bizarre until you release that they are imperialized approximations of metric approximations of 32nds of an inch. (I **** you not.) Why 32nds? Because this was how lumber yards specified the thickness of Bakelite laminate back in the 1940s when modern PCB technology was invented, and the first large-scale PCB fabricators simply ripped off the machines used to manufacture kitchen countertops.
The connectors used to make all these interconnects are a mishmash of different standards- some SAE, some metric, often both in the same part. Most of the newer stuff, blessedly, is all metric, even the American-made parts.
Except for large RF connectors. Those are typically specified in fractional inches, with a precision of 1/8". Except that these measurements don't actually refer to the size of the connector itself, but rather the "nominal" diameter of the equivalent copper plumbing pipe from which the first large-diameter RF hardlines were produced shortly after WWI. To this day, we still refer to heavy RF cabling as "plumbing," and in fact many of the same tools are used to assemble it.
It's a miracle that we manage to actually build anything that works. I'm still waiting for a datasheet which specifies mating pressure in something like nanosthènes / parsec^2.
[/rant]
Last edited by Joe Perez; 08-21-2014 at 10:07 AM. Reason: Schpelling
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08-21-2014, 09:38 AM
#20
I would seriously doubt that it would at the time. Around the same time, the US and Germany were co-developing their next generation battle tank, the MBT-70. This project was eventually cancelled because of runaway costs. Part of the difficulties with the project was that all of the drawings had to be converted from Metric to SAE every time they were passed between the US and German design teams.
Another story involves the M60 machine gun project. Originally the US was going to copy the German MG42 of WWII fame. When the converted the drawings to the imperial system and re-chambered it for the 30.06 round, it jammed frequently. Finally the army gave up and adopted the much-maligned M60.
Also didn't NASA lose a mars lander to improper conversion more recently than the above stories?
I read anecdotally that the imperial system may be better suited for machine shop type work than the metric system. I am not a machinist though, so that may just be personal bias in what I read.
Another story involves the M60 machine gun project. Originally the US was going to copy the German MG42 of WWII fame. When the converted the drawings to the imperial system and re-chambered it for the 30.06 round, it jammed frequently. Finally the army gave up and adopted the much-maligned M60.
Also didn't NASA lose a mars lander to improper conversion more recently than the above stories?
I read anecdotally that the imperial system may be better suited for machine shop type work than the metric system. I am not a machinist though, so that may just be personal bias in what I read.
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