On 12/14/2011 3:59 PM, time-nuts-request@febo.com wrote:

I agree with you, and funnily enough the rest of the NATO world uses
7.62mm and 5.56mm rifles. (Both were originally based on standard inch
sized rifle cartridges designed in the US)

The problem in converting to metric would require replacing a lot of
tools. For example Mills, lathes, and other machining tools and
measurement devices are expensive, and last for decades. I doubt many
of the small tool shops around here could afford it.It's a great idea
to standardize in theory, but in practice it becomes difficult. Maybe
the whole world should standardize our language. We could all switch
to Spanish or Latin or Chinese to speak with so we could all talk with
each other. That would probably be more helpful to me on a daily
basis, than having to switch measurement systems.

While we're on the subject, let me throw time back into the mix. We
use months and days for scheduling projects. Meanwhile some of our
counterparts use calendar weeks. This is much more difficult to
convert between than inch and mm. When is CW 36???

There I threw some wood on the fire too!

Dan

On Thu, Dec 15, 2011 at 9:29 AM, Dan Kemppainen dan@irtelemetrics.com wrote:

Can you point one even ONE machine shop in the US that can make metric
parts?  Those guys would have gone out of business years ago.  Also
how many are still using hand cranks and reading veneer scales?  Even
small one man ships are using CNC now.

The US is slowly converting.  It will take a long time.  Even now if
you go to Home Depot and look at plywood you see the better (non
construction) grades sold in even millimeters with the inches being
some odd number of 32nds approximation.  This will slowly creep into
more and more products.

So the debate is silly.  If the US should convert???  No.  the only
question is how fast are we converting and when will we be fully
converted.  Not even if this will happen, it will.

Chris Albertson
Redondo Beach, California

On Thu, Dec 15, 2011 at 9:42 AM, Chris Albertson
albertson.chris@gmail.com wrote:

Obvious typo:  Should read "that can NOT make metric parts?"    The
inability to make "hard" metric parts means you can NOT sell to many
industries and the export market is also mostly closed to you.

Chris Albertson
Redondo Beach, California

What I find interesting is that the first push for standardization, at
least for machine threads, came from the manufacture of arms, the
Springfield Armory, at the time of the Civil war. At that time, threads
were a mixture of the then fledgling metric system (French) and a
conglomeration of American threads. Thread shapes were quite different
as well. The next big standardization came from- you got it- the
automotive industry (SAE is of course Society of Automotive Engineers),
and I guess, only a guess, that the reluctance to change to metric
really came from the automobile industry. At one time, the Volvo had
SAE, Metric, and Whitworth fasteners in it, and not too long ago at
that.
So, I think that manufacturing inertia rather than the housewife might
be to blame for the US still being SAE and all that implies. As bolts
go, so do the rest of the measurements.
Don

Chris Albertson

--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell

Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com

The laboratory where i work obviously reports results using the SI metric
system. There is one exception though, and that is the energy side,
specifically calorimetry. At first glance the calorimeters appear to
normal(SI, that is). They take mass in terms of the gram, measure
temperature by degree Celsius, and internal calibration is stored as
calories.

The exception is the result is reported in BTU/ pound!  How's that for
mixing systems?

On the electronics side of things it's even worse. Technical documents
mixing and matching between systems. It's very common to see specifications
cited partially in MKS and CGS with no correction terms.
FYI:
MKS = Milimeter Kilogram Second
CGS = Centimeter Gram Second

I've seen two other systems, but their names are eluding me at this time.
Also, I've come across bolts that are not SI, nor SAE. I believe they are
considered a british thread but i'm not certain.

Steve

On Thu, Dec 15, 2011 at 1:15 PM, Don Latham djl@montana.com wrote:

On Thu, Dec 15, 2011 at 2:43 PM, Steve . iteration69@gmail.com wrote:

Correction

There's a system that the motorcycle guys call the Whitworth Inch, but I think may be more correctly called Whitworth Measure.  It's an old British system that was used on their motorcycles and possibly cars, too.  There's a whole subculture of people trading in Whitworth tools for BSA and Norton owners.

-John

Those bolts would be whitworth.

On Dec 15, 2011, at 14:43, "Steve ." iteration69@gmail.com wrote:

The British Whitworth is a 55 degree thread instead of the 60 degree
SAE. BTU is a British Thermal Unit, hence BTU/lb. MKS is Meter Kilogram
Second, one of the precoursors to thee SI system.

Steve .

--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
R. Bacon
"If you don't know what it is, don't poke it."
Ghost in the Shell

Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com

Hi Chris:

Yes.  In hospitals they are measuring your height in feet and inches, but your weight is in kg (6' 1" 120 kg).  Sort of
like tire sizes which use inches for the wheel diameter and mm for the section width (P215/65R15 - 215mm section width,
15" rim diameter).

Even more interesting than the metric/English idea is that my local shop (all CNC) has a no extra cost tolerance that's
ten times tighter than the no extra charge tolerance (+/-500 Millionths) an experienced machinist can hold (+/-5 mils)
and they have coordinate measuring equipment to back up the much tighter tolerances you can get for the extra charge.

A related story is that back in the 1960s I was designing microwave parts, many of which were made on a lathe.  There
was a local shop that had chucker lathes (our company shop also had one) but this local shop would always come in below
the in house and competitive bids.  These all used "5C" collets.
http://www.prc68.com/I/Lathe.shtml
http://www.prc68.com/I/DrillPress.shtml#5C
It turned out the the low bid shop had a screw machine in the back room that was kept a secret for maybe a year or two.
The chuckers were really not being used to make parts.  But now screw machines have been replaced by fancier CNC
machines like the "12 Axis CNC Mill Turn Centers".

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Brooke4Congress.html

Chris Albertson wrote:

The idea that conversion to metric would require replacing all of the machine tools (lathes, mills, etc) is a myth. Any U.S. machine shop has walls and toolboxes covered in conversion charts, converting drill, screw, wire, sheet sizes from one crazy measurement to another. One single additonal conversion chart, inch to metric, and you can keep using your inch machines on metric projects.

My mill has inch lead screws. I added a low cost digital readout with a little button to show inch or millimeter movements, and now I do everything in metric. No problem.

Don Couch

--- On Thu, 12/15/11, Dan Kemppainen dan@irtelemetrics.com wrote:

Hi Don:

Sure converting lengths is easy and I have metric, English and weird taps and dies, but how do you turn metric threads?

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Brooke4Congress.html

Don Couch wrote:

On 12/16/11 8:00 AM, Don Couch wrote:

20-30 years ago (when Space Shuttle, a notable user of inch/pound, was
being designed and built) this was not the case.  An awful lot of stuff
was done with machine tools that were designed and built in the 1950s or
earlier, and things were done with gear trains to set the feed rate, etc.

All those gear ratios were designed to produce that 20 threads/inch,
etc. and changing gears is a big deal: once you've got the shaft to
shaft distance fixed, there's only certain ratios that "work", unless
you want to start making gears with weird shaped and sized teeth. That
is a big tooling expense.

This is still the case for a lathe. Sure, you can do "electronic gear
boxes" but then you need multiple motors, rather than just driving
everything off one.  And having it geared means that even if the motor
slows down, the ratio of along to around stays fixed.

With CNC, life is easier.

Sometimes we forget that not too long ago, there was no such thing as a
"low cost digital readout", and CNC was fairly rare.

Today, though, a "big bang" conversion would be a lot easier.  It is
just a matter of pushing a button, since the "gearing" is done
electronically for the most part. Ditto for displays.  My car displays
temperatures in F or C with a push of a button.  Back in the 70s when
we last ventured forth into metrication, it would have been much tougher.

And to keep this tangentially timenuts related..  I ran into this whole
"not just any gear ratio is possible" when trying to make a Mars Clock
back in 2003.  There was some guy making Mars wristwatches (a
fashionable accessory for the folks doing MER ops). So I thought about
getting a clock and some gears from Small Parts or Boston:  I talked to
a friend who had made a couple Orreries (which have similar needs); and
learned some practical experience about gear trains.

I took the easy timenuts way out:  Buy a cheap battery clock with a 24
hour movement, rip the 32.768kHz crystal out, drive it with a HP3325B
set to slightly less to match the Mars day length, locked to the
Hydrogen maser on lab, thereby producing the world's most accurate Mars
clock.  Sure, there was this piece of coax running from the 3325 under
my desk out the door to the clock out in the hall, but hey, it worked.

Which ones?

Some time ago I was setting up to turn a Metric and discovered that there where a Japanese Metric standard for the thread as well as a German Metric standard both of which where slightly different from the "standard" Metric threadd that was I wanted to cut.

Cheers, Graham ve3gtc

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Brooke Clarke
Sent: December 16, 2011 11:49
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] metric / English

Hi Don:

Sure converting lengths is easy and I have metric, English and weird taps and dies, but how do you turn metric threads?

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Brooke4Congress.html

Don Couch wrote:

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

With a metric tap & die set?
:-)

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Brooke Clarke
Sent: 16 December 2011 16:48
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] metric / English

Hi Don:

Sure converting lengths is easy and I have metric, English and weird taps
and dies, but how do you turn metric threads?

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Brooke4Congress.html

Don Couch wrote:

machine tools (lathes, mills, etc) is a myth. Any U.S. machine shop has
walls and toolboxes covered in conversion charts, converting drill, screw,
wire, sheet sizes from one crazy measurement to another. One single
additonal conversion chart, inch to metric, and you can keep using your inch
machines on metric projects.

little button to show inch or millimeter movements, and now I do everything
in metric. No problem.

time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Not that hard, actually. My 1984-vintage lathe has an inch lead screw, but
the quick-change box that drives the leadscrew will do all of the inch and
most metric threads directly. The few "weird" metric pitches are
accommodated by changing two gears on the input side of the QC box. I
suppose that at some very small level, there is some "error" in the metric
threads produced (and I've never bothered to calculate it for my lathe) but
it's a VERY small error that has never been an issue for me.

73,

geo - n4ua

On Fri, Dec 16, 2011 at 11:48 AM, Brooke Clarke brooke@pacific.net wrote:

On Fri, Dec 16, 2011 at 8:48 AM, Brooke Clarke brooke@pacific.net wrote:

How would you cut 40 tpi or 24 tpi?  You put in the "correct" gears to
drive the lead screw so the tool moves at the desired rate

To cut metric threads they use a gear with the correct ratio to drive
the lead screw.  Yes if the lead screw is 1/8 inch the drive gears
will have some odd ratio but it works.  The reason it works is
because back in 1959 they re-defined the inch to be an EXACTLY 25.4mm.
From then on gears with integer number of teeth will do the
metric/imperial conversion perfectly.

I think I said a while back that any machine shop that can't figure
this out has likely already gone out of business.

Chris Albertson
Redondo Beach, California

You use the change gears in a ratio of 127:50 (254:100)

-John

==============

There is no "error" with the change gears. The ratio of inches to
centimeters is exactly 1:2.54 or 100:254 or 50:127. It is often done with
a train of 3 gear pairs to get the center-to-center shaft spacing right.

-John

=================

On Fri, Dec 16, 2011 at 9:45 AM, George Dubovsky n4ua.va@gmail.com wrote:

. I

No error.  They fixed that problem 50 years ago by simply redefining
all Imperial lengths to be exact integer ratios of the meter.  the
inch is exactly 25.4mm.  Ages ago 25.4 was only a "close"
approximation but since 1959 it has been exact.

So in a small way we already converted to the metric system 50 years
ago.  Miles, yards, feet, inches all are legally defined for the last
50 years by their relation to the meter.  And as I said those
relations are NOT approximations, they are definitions.

Chris Albertson
Redondo Beach, California