That state of metric conversion in the US

[rickman]

I once found a US Army specification for a piece of electronics
equipment that listed the maximum weight in grams and the maximum
dimensions in inches.

Off-topic a bit, but I have copies of two successive pages in a US
Navy spec. On one page, all that is written except for the document
header and page number is "This page intentionally left blank". The
next page just has the document header and page number.

Obviously one page was intentionally blank and the other was an
accident. I hope no one lost their job over that! lol

 

[rickman]

Hello,

but if 1/4 = 6.35 mm is too thin and 3/8 = 9.53 is too thick, there is
also 5/16 = 7.94 mm or 9/32 = 7.14 mm.
If you want something like 5 mm, you may specify 2/10 inch which is 5.08
mm. 4/10 is 10.16 mm and 3/10 is 7,62 mm.
If they want to divide by powers of two, no problem, 13/64 is 5.16 mm.
19/64 is 7.54 mm. If more precision is needed, 1/256 is 0.09921 mm,
50/256 is 4.96 mm.

Just a little flexibility.

I'm sorry, I don't quite get this. What is 4 mm in fractional inches?
For that matter, if I want 0.1 inches what standard fraction should I use?

 

[Spehro Pefhany]

Do you think a 6 mm square head isn't going to work ok with a 6.35 mm
square socket hole? I don't think the 0.35 mm difference (if it is that
much) will even affect the detent. Am I wrong about this? I expect a
square connection would be much more forgiving of size mismatch than a
12 point socket on a hex nut.

The difference (between socket and driver) is less than 0.2mm on a
1/2" socket. A 12mm driver would more than quadruple the slop. Might
not be healthy if you're trying to free a frozen bolt.

Sounds like a good reason to just give in and spend the extra few bucks
to get the metric stuff. I wonder how the rest of the world manages?
It much be a PITA knowing they are paying too much for their tools.

It's not just spending the extra bucks once, I'm quite willing to do
that (and have with some machine tools), it's the continuing supply of
a wide range of metric sizes of cutters, taps, reamers and such like
that causes hassles. I've actually gone backwards (more inch stuff)-
with calipers and micrometers and DROs that switch, it's not so bad.
I'm certainly not going to try to find boutique suppliers of A4 paper
and fittings for whatever Europeans use instead of NPT threads. It's
not like the inch numbers mean much anyway.. 1/4-NPT is 0.54"
diameter, for example. At least the TPI numbers mean something. The
taper is 3/4" per foot. ;-) And chucks etc. use JT tapers and Morse
tapers and R8 tapers, which are inch. It's a dog's breakfast. 20 gauge
stainless sheet is thicker than steel, which is thicker than aluminum.

I'm sure the metric tools are cheaper and more available than inch are
outside North America, but I'm not there. Somtimes I'll bite the
bullet and pay 100x the going price for metric fasteners when

There are plenty of times when I get tired of trying to do the math on
feet, inches and binary fractions of an inch. Where do I mark cuts on a
board 3 ft, 3 3/8 inches long to space out three notches 1 5/16 wide so
the un-notched areas are all the same width? With all round metric
values I can do that in my head. 33 1/3 mm notches and 225 mm
un-notched areas.

I remember conversion cards to go between decimal and fractional inches.
I've never seen anything like that for metric. Living in the metric
world is the best way to go, living in both worlds is the worst way to go.

It's nice to have the imperial units sometimes.. for some
applications, BTU/hr*ft*°F might be just the ticket. But usually I
find the metric makes life easier. Living in both worlds gives a bit
more variety in things at times too. Letter size drills, drill wire
gauge sizes, metric drills, fraction inch drills- there's bound to be
something that makes a hole I can live with.


Best regards,
Spehro Pefhany

 

[Spehro Pefhany]

Isn't that a bit of a harsh reply? If they guy tried a 14 mm socket and
it was too small, that would be pretty convincing proof that the nut was
9/16 inch and not metric. I don't automatically assume someone like
Joerg is an idiot.

I find it more likely that some device might have been in use long
enough that it had not been converted to metric yet. But then I haven't
examined every nut and bolt used in building cars. Have you?

Must have been a strange vehicle to have required such a big stepper
motor.

;-)

Here's more on SAE vs. Metric on some GM products

http://www.crankshaftcoalition.com/wiki/Starter_motors



Best regards,
Spehro Pefhany

 

[josephkk]

A pint of what? Scotch, maybe? 20 ounces Imperial is 1-1/4 pounds of
water, more or less exactly. 16 US ounces of water is about 1.04 pounds.

Cheers

Phil Hobbs

Most common kitchen cooking ingredients, within a few percent.

?-)

 

[Syd Rumpo]

lol, does that mean 47 kph is 2A mph? It works when the single digit
miles are 0, in other words, when miles are multiples of 10.

Hey, I never said it was perfect! And how do you get 2A from 47?
Metrician, heal thyself.

Cheers

 

[Tauno Voipio]

A nautical mile is a minute of arc on the great circle. It just
happens to be about 6000 feet.

Approximately. A minute of arc is slightly less than 1 nm at the
equator and slightly more just shy of the poles. About a 1% change
overall [Bowditch 2002, Table 7]. You're correct, though, that for
practical navigation purposes, using one's dividers on the latitude
scale of a Mercator projection yields distance in nm. And yes, it is
just a happy coincidence that it works out to be roughly 2000 yds.
Handy, though.

We are using Lambert projection in VFR aviation charts, so a plotter
(a special ruler) works well without need to go to the latitude scale.
Also, the great circle heading can be taken directly from the chart.

Here, at 60 degrees North, the longitude scale on a Mercator chart
is just half of the full measure.

By the way, both captains (Mercator and Lambert) were teaching at the
Amsterdam Institut for Navigation, quite some time ago.

 

[[email protected]]

josephkk wrote:
On Sat, 16 Feb 2013 08:58:41 -0700, Jim Thompson

rickman wrote:
[snip]
Heck, I
worked at a company just a few years ago that made push to talk radios
for the US military. I was surprised that the mechanical engineers were
still using inches and converting all the metric stuff rather than doing
it all in metric!

Surprised? Some of my work is in aerospace. There it's all inches,
pounds, PSI, slugs, knots, feet and so on. To some extent that is even
so in the medical device industry. The topper:

[snip]

You forgot "Jerk"... the derivative of acceleration... used in
elevator specifications >:-}

...Jim Thompson
That reminds me of the day i saw dA-dt on a licence plate.

Maybe I should get this vanity plate: *PHUT*

No asterisks. Maybe you could get "PHUTTER". ;-)

In California you can get asterisks. Even heart shapes AFAIK. It's crazy
out here.

First I've heard of non-alphameric characters in license plate
numbers. I wonder how other states handle it in their software?
The strangest thing I've seen here on license plates were Auburn and
LSU logos (on GA plates). GA and GA Tech, I understand but the
competition? I guess if they can get you to volunteer $25/yr to the
treasury, why not?

 

[[email protected]]

Is that because of the huge shadow he casts? Probably due to the all
the burgers he rams down his gullet.

No, he's just that dim. He's called DimBulb for a reason.

 

[[email protected]]

This happens a lot does it?

Once is enough to ruin your whole day.

 

[David Lesher]

sockets also come in 3/4" and 1" for larger problems.

Larger opportunities!

 

[rickman]

The difference (between socket and driver) is less than 0.2mm on a
1/2" socket. A 12mm driver would more than quadruple the slop. Might
not be healthy if you're trying to free a frozen bolt.

Are you talking about the socket that fits the bolt or the square drive
hole in the socket that fits the ratchet? I agree that a socket has to
properly fit the nut, mainly because the corners are easier to round off
especially when using a 12 point socket. But the drive hole is square
and much more robust. I seriously doubt that 0.35 mm of extra clearance
is a problem for a 1/4 inch drive socket or an extra 0.5 mm clearance on
a 1/2 inch drive socket.

It's not just spending the extra bucks once, I'm quite willing to do
that (and have with some machine tools), it's the continuing supply of
a wide range of metric sizes of cutters, taps, reamers and such like
that causes hassles. I've actually gone backwards (more inch stuff)-
with calipers and micrometers and DROs that switch, it's not so bad.
I'm certainly not going to try to find boutique suppliers of A4 paper
and fittings for whatever Europeans use instead of NPT threads. It's
not like the inch numbers mean much anyway.. 1/4-NPT is 0.54"
diameter, for example. At least the TPI numbers mean something. The
taper is 3/4" per foot. ;-) And chucks etc. use JT tapers and Morse
tapers and R8 tapers, which are inch. It's a dog's breakfast. 20 gauge
stainless sheet is thicker than steel, which is thicker than aluminum.

I'm sure the metric tools are cheaper and more available than inch are
outside North America, but I'm not there. Somtimes I'll bite the
bullet and pay 100x the going price for metric fasteners when
something is going to be assembled offshore.<shrug>.

Last time I checked, I could buy tools from anywhere. But I don't often
use pipe threads and machine shop tools, so I'll defer to you on this.
My point is that unless you are close to retirement, it is a losing
proposition. Pay me now, or pay me later...

It's nice to have the imperial units sometimes.. for some
applications, BTU/hr*ft*°F might be just the ticket. But usually I
find the metric makes life easier. Living in both worlds gives a bit
more variety in things at times too. Letter size drills, drill wire
gauge sizes, metric drills, fraction inch drills- there's bound to be
something that makes a hole I can live with.

I don't know what ticket that would be. I'll be a very happy guy to see
the measurement system we are using go the same way as British money.

 

[rickman]

A pint of what? Scotch, maybe? 20 ounces Imperial is 1-1/4 pounds of
water, more or less exactly. 16 US ounces of water is about 1.04 pounds.

But a pint is *exactly* 16 fluid ounces...

 

[rickman]

Sure, but nowhere near as accurately as 1 imperial gallon = 10 lbs of
water. PS in the UK a pint isn't a pound.

In the UK "A pint of pure water is a pound and a quarter".

 

[rickman]

Part of the reason is that one nautical mile is (about) 2000 yards,
making lots of mental calculations much easier. It's formally defined
as 1852 meters but that's kind of unwieldy for most people trying to
do math in their head.

Wait a minute. If they went metric, they wouldn't be using nautical
miles either...

Speaking of that, I believe the reason they use nautical miles is
because it is approximately (pretty close actually) to one minute of
longitude at the equator or latitude anywhere. I guess that comes in
handy. While verifying this I found a very interesting page that
explains the origin of the term "knots".

http://www.onlineconversion.com/faq_07.htm

 

[Tim Williams]

Re: jokes,

I must say, I'd rather be drinking this Russian Imperial Stout than, say,
a French Metric Porter. Mmmmm, nummy.

Tim

 

[cameo]

Strangely, in the UK we give a US pint of blood instead of the larger
imperial measure.

They don't want to bleed you dry perhaps?

 

[George Herold]

I don't see what you're getting at...One US fluid ounce of water is
about 1.04 ounces avoirdupois, not 1.00.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text -

- Show quoted text -

Sure but +/-5% is good enough lots of times. I've used 8lbs in a
gallon which is ~231 cu inches.. and an acre is ~22,000 sq feet. Lots
of silly non-metric coversion factors are stuck in my head.

My personal 'system' gripe is with temperature. Everyone should learn
Kelvin right off... about 296K in my house now. Having negative
temperatures is silly. Like you would be negative feet tall till you
reached five foot. (Hmm still working on distance, metric-wise.)

George H.

 

[Joerg]

josephkk wrote:
On Sat, 16 Feb 2013 08:58:41 -0700, Jim Thompson

rickman wrote:
[snip]
Heck, I
worked at a company just a few years ago that made push to talk radios
for the US military. I was surprised that the mechanical engineers were
still using inches and converting all the metric stuff rather than doing
it all in metric!

Surprised? Some of my work is in aerospace. There it's all inches,
pounds, PSI, slugs, knots, feet and so on. To some extent that is even
so in the medical device industry. The topper:

[snip]

You forgot "Jerk"... the derivative of acceleration... used in
elevator specifications >:-}

...Jim Thompson
That reminds me of the day i saw dA-dt on a licence plate.

Maybe I should get this vanity plate: *PHUT*
No asterisks. Maybe you could get "PHUTTER". ;-)

In California you can get asterisks. Even heart shapes AFAIK. It's crazy
out here.

First I've heard of non-alphameric characters in license plate
numbers. I wonder how other states handle it in their software?
The strangest thing I've seen here on license plates were Auburn and
LSU logos (on GA plates). GA and GA Tech, I understand but the
competition? I guess if they can get you to volunteer $25/yr to the
treasury, why not?

Some are a bit gross though:

http://www.r8pl8z.com/wp-content/uploads/2011/07/love-to-fck-funny-license-plate.jpg

Then the macabre ones:

http://www.r8pl8z.com/wp-content/uploads/2010/09/UARNEXT-funny-license-plate.jpg

 

[Robert Baer]

Here in Australia, where we've gone all metric already, I'm still
struggling with the concept of a metric pinch of salt.

Sylvia.

Ask a crook for a pinch..