That state of metric conversion in the US

[Fred Abse]

And chucks etc.
use JT tapers and Morse tapers and R8 tapers

You forgot about 30mm, 40mm and 50mm International tapers. Ubiquitous on
CNC machines. Better for automatic tool changing.

 

[[email protected]]

On Sun, 17 Feb 2013 00:10:51 -0800, MrTallyman



"10E8" is ambiguous. Some people think this is 1e8, and some people thinkit's
1e9. Most calculators and programming languages will treat it as 1e9.

10^8 = 1E8 <> 10E8

and in engineering format the exponent should generally be multiples
of three

-Lasse

 

[[email protected]]

You mean 2.54 mm connectors? That is what the Europeans call them.

Good Lord, you're dense. Who the **** cares what Europeons *call*
anything?

I see true metric a lot more often at 2mm, 1mm and even 0.5mm pitch.

You don't get out much, obviously. Just a small sampling of *one*
variety of connector (in inch sizes) from DigiKey:

http://www.digikey.com/scripts/dkse...9=216&PV89=92&PV89=86&PV89=15&PV89=56&PV89=94

 

[Tim Williams]

Actually these days I don't bother with prescription glasses so much. I
have two pair of reading glasses, one for the computer and one for
driving. Using the computer with the lower half of bifocals just isn't
for me. Too hard on the neck.

Flip them upside-down?

Tim

 

[[email protected]]

I tried exactly one pair of no-line (Varilux) bifocals and gave them
back. For any given distance there is exactly one pencil diameter spot
that will give you focus and I spent all my time moving my head around
looking for it. What a PITA! So I gave up on vanity and got lined
bi-focals and never went back. With very strong astigmatism in one eye,
the variables just didn't hack it.

I have one pair of no-line bifocals that I use for reading and for the
computer that work very well. I have exactly the problem you describe
with the *expensive* ones I just bought for driving. When I turn my
head to look sideways, nothing is in focus. It's worse than driving
without glasses. ...and forget them for reading. As you note, there
is exactly one spot that's in focus and everything warps around that.
I just received my second pair with that prescription in the mail
(normal bifocals from Zenni). We'll see how they do (at 1/5th the
cost, even with photo-gray).

Actually these days I don't bother with prescription glasses so much. I
have two pair of reading glasses, one for the computer and one for
driving. Using the computer with the lower half of bifocals just isn't
for me. Too hard on the neck. Much better to have a pair of glasses
where the entire lens can be used to view the screen. Also, when I drop
them and they get scratched, I spend another $6 and get a new pair. I
tried the $1 glasses, but they were pathetic. There really isn't much
in a dollar store that is actually worth buying at a dollar, even if it
is made in China. I guess you can get four quarters that you can use to
buy penny candy.

I need the prescription glasses anymore for the astigmatism
correction. I have two pairs for computer and reading, with the tops
set for about 20" and the bottoms for about 10". I could probably use
both of them a little farther out.

 

[Nico Coesel]

Hello,

it is not very nice to manually rout a PCB when you got a mix of parts
with different pin distancesbased on inch and mm, for instance 100 mils
and 2 mm.

Most (if not all) PCB layout programs have a function which snaps to
the centre of the pads when routing a trace. So different pitches are
no issue at all when routing a board. If it is, its time to look for
the 'snap to pin' function and switch it on or upgrade the PCB
package.

 

[Nico Coesel]

If you are in the US you must be the only one! Every once in a while I

I'm not in or from the US. I just conform to what is easy to use. I've
encountered a lot of people insisting on using A4 sheets in Orcad. I
have to duck when I say I just check 'fit to paper size' before
printing and use the default sheets. There is a nasty bug in Orcad
when using A4 paper sizes BTW.

metric exactly, but not the other way so much). Some foreign vendors
expect metric dimensions and give metric design rules. One thing that
always bugs me is when I do a metric based layout and get design rule
errors because something is 9.84... mil instead of 10 mil. Or I have
even seen design rule checking tools barf on 9.999... which turns out to
be round off error in the durn tool!

Been there... I recently submitted a design which got turned down. The
annular ring around a hole was 0.124mm instead of 0.125mm.

 

[Spehro Pefhany]

It's impressive how quickly we become famous.

In the future, everyone will be world-famous for 15 milliseconds.
-- S. Pefhany aka anon


Best regards,
Spehro Pefhany

 

[Jasen Betts]

There are no such thing as european numerals, the
ones we use are of arabic origin.

Indeed, we got them from there, and they got them from India.
Ours don't look much like theirs, and theirs don't look much like the
indian ones.

So, in the plate
you're referring to, there are arabic numerals on
the left and someting else in arabic on the right.

The Arabic charcters on the right are numerals.

If the arabaic stuff on the right were numerals,
you'd have recocgized them.

having encountered them before, I did.

http://en.wikipedia.org/wiki/Arabic_numerals

http://en.wikipedia.org/wiki/Numerical_digit

 

[Jasen Betts]

Actually the larger pages are better ratios (closer).

11x8.5 = 1.2941
17x11 = 1.5454..

you seem to be using x for division

22x17 has ratio 1.2941 which is 2^0.372...
34x22 has ratio 1.5454 which is 2^0.628...

A4 paper has ratio 2^0.5

on a logarythmic* scale both are equidistant from the sqrt(2).
this can probably be proven to be true for any arbitrary starting
dimensions.

*does any other system make sense for comparing ratios?

 

[rickman]

It's impressive how quickly we become famous.

Yes, the lag time is about the same as the duration... 15 minutes.

 

[rickman]

Mine is quite well adjusted -- I see a tinge of red from the bottom-right
edge, maybe half a pixel out. Rest of the display is quite well adjusted.
After dialing in, I haven't had to change it for years -- wish my circuits
were as stable!

Oddly enough, when I read black text on white background of just the
right pitch on my laptop, it tinges in red. I really shouldn't have
tried to scrimp on the computer and bought one with an LCD screen
instead of a CRT! lol But really, I get red tinging sometimes on
smaller fonts.

 

[rickman]

One foot per nanosecond is a useful, easy to remember approximation.

Yes, but it doesn't apply to circuit board which is where I care about
the speed of light mostly. Instead it is around 200 mm per ns depending
on your board construction.

 

[rickman]

and in engineering format the exponent should generally be multiples
of three

-Lasse

Tell that to the spreadsheet people! I recently found that you can make
engineering notation work in spreadsheets, both Excel and Open Office.
But it is not built in and it quite a trick getting it to work.

 

[Mr Stonebeach]

....
Indeed, we got them from there, and they got them from India.
Ours don't look much like theirs, and theirs don't look much like the
indian ones. ....
The Arabic charcters on the right are numerals. ....
having encountered them before, I did.

You're right, it seems I tried to be smarter than I am,
thanks for pointing this out.

Regards,
Mikko

 

[whit3rd]

Japanese screws aren't Phillips, but Pozidriv.
...Using a Pozidriv screwdriver on a Phillips screw works fine. Using a
Phillips on a Pozidriv screw is almost guaranteed to wreck the screw.

NO! Pozidrive flutes are constant-width.
Philips are tapered, and that means only a small contact
area between Pozi driver and Philips fastener- you'll deform
something.
JIS (Japanese) is a completely different series. So is "Reed and Prince"
(aka "Frearson"), except there's only one Reed and Prince size/shape driver.

A dot on the screw head indicates JIS
Four hash marks on the head indicates Pozidrive.


Pozidrive #1, #2 and Philips #00, #0, #1, #2, #3 are relatively
common, and NONE of them is a substitute for any other. Unless
you have an emergency do NOT mix drivers.

 

[[email protected]]

You have totally lost me on this one.  Who was talking about 9/64ths?
The original point was that it may not be hard to turn fractions into
other types of numbers, but converting other measurements into
fractional inches is a PITA.  The questions was, what is 4 mm in
fractional inches.  I don't get why 10/64ths would be given in place of
5/32.  I don't think I even have a measuring device that is marked in
64ths of an inch other than possibly a 6" steel rule that I don't even
know the whereabouts of at the moment.

My point was that metric is just a better way to go, in part because all
the measurements are decimal which is just so much easier to work with
in nearly all situations.

No, Uwe had a good mental shortcut for converting fractional inches to
mm--multiply 1/16ths by 16, divide by 10. The result is high by .8%,
but easy to compute.

Example: 13/16" (20.64mm). 13x16=208, divided by 10 ~= 20.8mm.
Example: 1/4" (6.35mm) = 4/16ths. 4x16 = 64, divided by 10 = ~6.4mm.

It works because 256 is just 2 more than the exact conversion factor,
which is 254. If the number's in 1/16ths, they've already done half
the work.

Thanks Uwe.

 

[[email protected]]

Oddly enough, when I read black text on white background of just the
right pitch on my laptop, it tinges in red.  I really shouldn't have
tried to scrimp on the computer and bought one with an LCD screen
instead of a CRT! lol  But really, I get red tinging sometimes on
smaller fonts.

it is probably "ClearType" it is Microsofts implementation of
enhancing the
resolution of text by "abusing" the known RGB layout of LCD screens
effectively
getting more pixels at the price of a slightly wrong color on the
edges

doesn't work on CRTs or rotated LCDs because the layout is different

you can try turning it off

-Lasse

 

[[email protected]]

You could send your eyeballs out for recalibration, if you have the
time to wait. ;-)

According to the eye doc, that may not be too many years off (small
cataract). ;-)

The problem then is which do I want, glasses for close work, or
glasses to see. ;-)

 

[Tim Williams]

doesn't work on CRTs or rotated LCDs because the layout is different

Ironically, it works reasonably well on some CRTs -- Trinitrons actually
have the same RGB stripe design.

Tim