Machining and Carpentry

[Brian]

I know this is not the right newsgroup for this question, but I could not
find a more appropriate one. I was wondering if anyone knows how
engineering and carpentry and other similar disciplines do decimals and
fractions in Europe and other countries where SI units are used. In the
U.S.A. we still use the English system where we use the foot and 12 inches
per foot. Then for smaller units other than the inch, we divide it into
fractions - 1/2, 1/4, 1/8, 1/16, 3/8, 3/16, 1/32, 1/64, 3/64, etc. I was
wondering how measurements are done in countries with the metric system in
place. I would assume they use centimeters in situations where we would use
inches like Carpentry. However, what about smaller units than the
centimeter? I would assume millimeters are used instead of fractions of
inches like we use. Am I correct? Also, what about units smaller than a
millimeter? For example, a millimeter is .0394 inches. That is close to
1/32 of an inch. What would a machinist do for units smaller than a
millimeter? Decimals of a millimeter? Do they use fractions of
millimeters? If so, do they use the same types as we do - 1/2, 1/4, 1/8,
1/16, etc, of a millimeter or do they divide it consistent with the metric
system as such - 1/5, 1/10, 1/20, etc. to give you decimals consistent with
the base 10 the metric system uses? Does anyone know? Anyone on this
newsgroup an engineer in a country that uses SI?

 

[Anthony]

I know this is not the right newsgroup for this question, but I could
not find a more appropriate one. I was wondering if anyone knows how
engineering and carpentry and other similar disciplines do decimals
and fractions in Europe and other countries where SI units are used.
In the U.S.A. we still use the English system where we use the foot
and 12 inches per foot. Then for smaller units other than the inch,
we divide it into fractions - 1/2, 1/4, 1/8, 1/16, 3/8, 3/16, 1/32,
1/64, 3/64, etc. I was wondering how measurements are done in
countries with the metric system in place. I would assume they use
centimeters in situations where we would use inches like Carpentry.
However, what about smaller units than the centimeter? I would assume
millimeters are used instead of fractions of inches like we use. Am I
correct? Also, what about units smaller than a millimeter? For
example, a millimeter is .0394 inches. That is close to 1/32 of an
inch. What would a machinist do for units smaller than a millimeter?
Decimals of a millimeter? Do they use fractions of millimeters? If
so, do they use the same types as we do - 1/2, 1/4, 1/8, 1/16, etc,
of a millimeter or do they divide it consistent with the metric system
as such - 1/5, 1/10, 1/20, etc. to give you decimals consistent with
the base 10 the metric system uses? Does anyone know? Anyone on this
newsgroup an engineer in a country that uses SI?

I'm an engineer in the US that uses metric exclusively. (Germany parented
company).
We do precision machining in high volume.
The common names of metric units and some info, note that, for lack of a
better term at hand, the 'base' unit changes depending on the length of
the measurement:
Meter: Typically used only where the measurement exceeds 1 Meter, and is
the common used base unit for large measurements, not exceeding a
kilometer.
Centimeter: In my experience, rarely used, see next
Millimeter: Generally regarded as the normal everyday base unit, above 1
mm and below 1 M, although it is common to see dimensions of much more
than 1 M given in mm (i.e. 1500mm = 1.5M)

Below 1 mm, microns are generally taken as the base unit.
0.1 mm: Generally referred to as either 'tenths' or 'one hundred microns'
0.01 mm: Generally referred to as either 'hundreths' or '10 microns'
0.001 mm: Universally referred to as 'microns'
0.0001 mm: Typically referred to as 'tenths of a micron'

The metric system, once you are used to it, is MUCH easier than the US
system.
I wasn't really exposed to it heavily until I started my current job in
my mid-20's. I had been through machinists school using US units. Now
that I have come to use it daily, I can barely do US units anymore. Even
in home carpentry, I use a tape graduated in metric units.

--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

 

[Brian]

How is that tape measure divided out? Like on an english tape measure it is
divided out to feet, then inches, then fractions of inches down usually to
1/32nds. So on one of these metric tape measures, how is it layed out? All
in millimeters?

Another question - for example let's take a common unit of measurement in
the english system a carpenter might use - 1/4 inch. That would be close to
6 millimeters. Let's say a machinist (or carpenter) was using a little
smaller than that - 5 millimeters. Now, he wants to cut it in half. Does
he call it 1/4 of a centimeter, or as it appears people are saying he would
call it 2.5 millimeters? In the english system, if you want half of 1/4,
you would use 1/8 inch. What if he wants to cut the 2.5 millimeters in half
again - does he then use 1.25 mm? In half again - .625 millimeters? Do
engineers using the metric system *never* use fractions like in the English
system? They always use decimals like I mentioned above?

Brian

 

[daestrom]

Decimals all the way.
I.e. smaller than a millimeter is 0.9mm or really smaller are
nanometers and picometers.
But they are all just meters without so many extra 0s.

Now for fun try to explain how to notate inches & feet addition. I've
had to, and learned a few things.

I got burned once when ordering a door. I needed a 3 foot wide door (36
inches). That is a common size, and is often notated as 3-0 (3 ft, 0
inches). But when it showed up, I got a 2-6 door (2 ft, 6 inches). The kid
behind the counter had taken down 3-0, but the one in the back ordered 30
(inches). Had to re-order and wait.

There are many times I wish we could just force an overnight change-over to
metric. Kind of like that one country that suddenly forced everyone to
drive on the other side of the road. A few painful moments, but 'tis the
sharp knife that cuts the quickest and hurts the least'.

daestrom

 

[Anthony]

How is that tape measure divided out? Like on an english tape measure
it is divided out to feet, then inches, then fractions of inches down
usually to 1/32nds. So on one of these metric tape measures, how is
it layed out? All in millimeters?

It is millimeters, every centimeter marked larger, every meter marked.
Much like inch/feet/yard on a typical tape. The one I use is graduated
in both inch and metric.

Another question - for example let's take a common unit of measurement
in the english system a carpenter might use - 1/4 inch. That would be
close to 6 millimeters. Let's say a machinist (or carpenter) was
using a little smaller than that - 5 millimeters. Now, he wants to
cut it in half. Does he call it 1/4 of a centimeter, or as it appears
people are saying he would call it 2.5 millimeters? In the english
system, if you want half of 1/4, you would use 1/8 inch. What if he
wants to cut the 2.5 millimeters in half again - does he then use 1.25
mm? In half again - .625 millimeters? Do engineers using the metric
system *never* use fractions like in the English system? They always
use decimals like I mentioned above?

That would be 2.5 millimeters and 1.25 millimeters, and finally, 625
microns.

You never use fractions in the metric system. Always use whole numbers
or decimals.

--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

 

[Brian]

. So on one of these metric tape measures, how is it layed out? All

Yes

No centemeters on it? Sounds like a lot of little lines with no real way to
read where you are. I'm assuming they must have centimeters to help you
keep track of where you are. Imagine a tape measure with nothing but
1/16'ths of an inch and no inches or feet. Only yards and 1/16ths of an
inch. That would be impossible to make measurements with.

I do high end finish carpentry. I have two years of engineering school
under my belt. In situations (e.g., panelling) where I have to divide
a distance by three or seven in the hexadecimal/binary system we use,
that doing the math, while well within my abilities, is a *very* clumsy
process.
Quick, what's a third of 11' 4 5/8" to the nearest sixteenth?
Now, what's a third of 347 cm to the nearest mm?

I was just trying to find out exactly how they do machining and engineering.
do they divide things into tenths or binary fractions. I guess what everyone
is saying is they use tenths, and don't ever use fractions the way we do in
the "imperial" system. BTW, I rarely use 1/10 of an inch. maybe 1/16 or
3/32. Just wondering how they divide things into smaller and smaller units
with the metric system (SI).

 

[Don Kelly]

----------------------------

No centemeters on it? Sounds like a lot of little lines with no real way
to
read where you are. I'm assuming they must have centimeters to help you
keep track of where you are. Imagine a tape measure with nothing but
1/16'ths of an inch and no inches or feet. Only yards and 1/16ths of an
inch. That would be impossible to make measurements with.




I was just trying to find out exactly how they do machining and
engineering.
do they divide things into tenths or binary fractions. I guess what
everyone
is saying is they use tenths, and don't ever use fractions the way we do
in
the "imperial" system. BTW, I rarely use 1/10 of an inch. maybe 1/16 or
3/32. Just wondering how they divide things into smaller and smaller
units
with the metric system (SI).

---------
The metric system is based on powers of ten.
nanometer (nm)=1/1,000,000 meter
millimeter (mm)=1/1000 of a meter
centimeter (cm)=1/100 meter
kilometer =1000m
megameter =1,000,000 meter

Common usage is in cm, mm or m and going up is km, etc
SI units use powers of 1000 - eg nm mm, m, Km, etc
However, a metric tape will have m, cm and mm marked just as an Imperial
tape will have feet, inches and fractions of inches (1/16, 1/8,1/4,1/2)
marked.
Plans may have mm marked (say 3250) or meters (3.25) marked.
Ditto layout for weights etc -factors of 10.

By the way, have you heard of "mils" as used im machining? 1 mil =1/1000
inch