Fractions

[curtiss]

Thought I would start a thread with this handy chart. Never seen these side by side before.

[Kyle Stapleton]

Been teaching Cadd for years and never have I seen this before.

[steve_g]

“Been teaching Cad for years and never have I seen this before…”

We sure used them when I was teaching mechanical drawing!

SG

[Kyle Stapleton]

With mm and in on the same chart?

Can say I never really looked it is just one click to convert from the two.

[steve_g]

Kyle…
There was a time when we taught students that “metric” was the future… A lot of emphasis was put on all things MM. I think we spent so much time with conversions that students never really got a feel for how “big” a millimeter was!

SG

[twelchPTM]

i have these charts all over my shop, starette packages them with some of thier precision measuring tools, and the mouse pad that came with my shopbot has it to.

[adrianm]

My SB mouse pad only has imperial fractions and their decimal equivalents on. There aren't any metric equivalents on it.

Do they do another one?

[bleeth]

Nope, that's it. You can find them on the internet though and just print and laminate it for protection. A lot of supplier catalogs have them in the book too like Hafele.
If you would like I also have a little conversion program Blum used to have available. Send me your e-mail and I'll let you have it. It goes both ways.
There's probably free phone apps too, although I haven't looked.

[rb99]

Kyle…
There was a time when we taught students that “metric” was the future… A lot of emphasis was put on all things MM. I think we spent so much time with conversions that students never really got a feel for how “big” a millimeter was!

SG

When I was in grade 7 or 8 the Canadian Govt switched the entire country of Canada to metric. WTF! I still never really got used to it. That was 35-40 years ago... Temperature in Celsius, weight in Kilos, gas in liters, mm; cm; meters etc. The sign trade still does most things in inches and feet though.

[myxpykalix]

I can't remember exactly where i've seen something like this...hmmmm:D

[jerry_stanek]

Hey jack where are the metric equivalent on that. I use mine all the time but now I need the metric measurements for other projects.

[adrianm]

Exactly my point from my earlier post. I think people are missing the fact that the original list that started the thread has imperial fractions, imperial decimal equivalents and metric equivalents.

Fractions converted to decimal is not the same thing as metric.

[Kyle Stapleton]

I have been told there is no true metric to English conversion. My thinking is that the conversion would leave an irrational number (like "pi" were the decimal never stops or repeats)

[myxpykalix]

Since i don't work in metric i guess i didn't think you needed that, however here is a handy conversion utility that will convert all kinds of things including what you need:
http://joshmadison.com/convert-for-windows/

[Zeron]

I have been told there is no true metric to English conversion. My thinking is that the conversion would leave an irrational number (like "pi" were the decimal never stops or repeats)

You were told wrong. In 1933 American Standards Association changed the definition of an inch to exactly 25.4mm following the British Standards Institution who did the same in 1930.

[steve_g]

Oh.. I thought it was still "three grains of barley, dry and round, placed end to end, lengthwise"

SG

[Brady Watson]

Oh.. I thought it was still "three grains of barley, dry and round, placed end to end, lengthwise"

SG

No, no, no. You're probably thinking in cubits! :D

Get a pen kit for your tool and make whatever chart you want for your shop. Hang it on the wall...You could include ANY conversion you want on the same chart.

Interesting the path some of these threads take. The road to hell ain't paved with asphalt...

-B

[dana_swift]

Kyle- I have the problem of having an inch based drill index, and both inch and metric taps. In the past I just figured out what drill to use each time I needed one. This thread got me thinking I could create a table of mm hole sizes and the nearest drill size above and below the exact size.

I have attached the PDF file of my results. Note there are 5 tables, each for different drill index step sizes.

Enjoy! And Merry Christmas :)

D


(PS this was done with a short program in C#)

[curtiss]

That is quite a chart Dana,

I suppose I could ask the next dumb question, do they make drill bits that come every 1/128th of an inch or even 1/256th ???

I don't think I even want to know...

[steve_g]

For you visual learners like me... I made a chart.

SG

[curtiss]

Steve, I now think I like your "Chart" best.

But I downloaded it, scaled it to the actual size of 1" wide, but now it is too hard to read....:confused:

[steve_g]

Well... I made the original 40” wide so I could see it without my glasses on! I was going to post it but it’s 16.6 meg...

SG

[scottp55]

Thanks everyone for programs/charts/visuals, now on desktop screen.
Sooo much easier if Pi=3 and the World was flat:)

[twelchPTM]

some one asked earlier in the thread and they are correct. True mathematical conversion from imperial to metric is impossible to do. While it will be pretty darn close, it is off but will only show if your looking for ultra precision. That is why in this day of computers and calculators chart like the ones being discussed here are still relevant.

[Kyle Stapleton]

And I thought my collage design teacher was blowing smoke (well more smoke) after reading some other post.
It came up in class when the Hubble telescope was being fitted with its "contact lens" because the US were using inches in our part of the design and the everyone else was using mm and that is why the first pictures were not in focus, thus the need for the new lens.
Again just what I was told, so if I'm wrong please do not kill me for it.

[ron brown]

I'd like one of those "Think Metric" signs .... make it about 24" X 16".

Ron

[steve_g]

Closest I can get to that will be 60mm X 40mm...

SG

[ssflyer]

I'm curious why a lot of people say that no true mathematical conversion from metric to imperial is possible. While there are some discrepancies in measurements other than length (for instance the difference in liquid measurement between the UK and US systems), length conversions should now be exact - 1" = exactly 2.54cm.

Here's an excerpt from an article on it:

"Even as late as the middle of the 20th century there were some differences in UK and US measures which were nominally the same. The UK inch measured 2.53998 cm while the US inch was 2.540005 cm. Both were standardised at 2.54 cm in July 1959."

Basically theThe Systeme International was adopted specifically to allow for exact conversions.

If I'm missing something here, please let me know! :)

[Kyle Stapleton]

Might be because the decimals get so looooong.
Ex:2.625" = 6.6675 cm which can be done easy on a calculator but try to make it.

Almost anything can be done on paper with math, but good luck making it.

Just a thought.

[ssflyer]

Hi Kyle,

Thanks for the reply. That makes sense to me, but also applies to unconverted values.

Example 1 3/32" = 1.09375" = 2.778125cm

While the conversion is exact, good luck making either, exactly. That's why machining tolerances are always specified on critical parts.

Probably me just overthinking - too much coffee this morning! :eek: