Why Metric?

I realize that the metric system is much simpler. After all what genius decided that 11/64ths was the way to go? I wondered why every STL file I download is in mm? I use Rhino 3D and always draw in inches. Am I the only one?

Yes.

Because most of the world uses the metric system and RepRap was invented in the UK, so mm has always been the convention.

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Is it conceptual that you open two duplicate topics in two different subforums?

Please don't.

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The reason for using metric is because Intel has never produced a CPU chip with a floating-DENOMINATOR fraction co-processor. Well, unless you count the early Pentium chips that thought nine squared was 81.000001.

Get with the program. Even Americans use metric.....

I have seen programs that ask if you are importing in mm or inchs.
I have tried importing using imperial and it makes the object 2.5 times bigger. Not good

I never liked having to think about a 64th of something, let oline an inch. I could not fathom the thought.
I can metric is easy. Microns, mm, cm, km and these value cubed, are their Litre Counterpart.

Metric is the world standard.
Was even supposed to be in america. But not all americans could not grasp it.
My mother in the 60s and 70s said they only had a few lessons in metric then it was all to hard to implement in all the schools

in sketchup you can design in inches. And export in MM, that may be there only to facilitate the imperials.

Try to measure a micron with a fraction of an inch, now say it five times fast...

Metric is a base 10 system. Easy to calculate. Most of the time you read inches as a fraction. While you can reinvent the wheel just to suit your needs it won't be practical. You'll have to remember we are using a low level computer that has to do a lot of calculations on the fly as it is (changing coordinates into steps per cm) If you throw fractions into the mix, that's just something else to go wrong.

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pushthatbolder
...I have tried importing using imperial and it makes the object 2.5 times bigger...

This is because there are 2.54 cm in 1 inch. The file was exported using a 1/1 scale.

There are a lot of industries that use fractional inches, but in aircraft we use primarily decimal inches (most commonly to three decimal places), so base-ten imperial isn't impossible. It's not a big deal to me either way. Develop the model in the system of units that is convenient for the application (which for a UK-based development would usually be metric) and export the STL in the units expected by the printer you're using. I've built models in both unit systems for export to both unit systems.

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KingRahl
Metric is a base 10 system. Easy to calculate. Most of the time you read inches as a fraction. While you can reinvent the wheel just to suit your needs it won't be practical. You'll have to remember we are using a low level computer that has to do a lot of calculations on the fly as it is (changing coordinates into steps per cm) If you throw fractions into the mix, that's just something else to go wrong.

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pushthatbolder
...I have tried importing using imperial and it makes the object 2.5 times bigger...

This is because there are 2.54 cm in 1 inch. The file was exported using a 1/1 scale.

Yes i know that. I was just stating it to support my post.. i know how measurement and numbers work

Sorry about the double post. I thought that I had deleted the first one. I guess not. Thanks for the replies. It sounds like it is time to conform or be cast out. Once again America is wrong thinking that it holds the high ground. That's why an earlier Mars mission inpacted the surface. One guy designing in mm's and another in inches. I'm going to buckle down and set Rhino up for mm's. Something new to learn and that's what it's all about.

I am 50 and always worked in fractions and decimals. Since I got into 3D printing I am learning metric and I really, really wish the U.S. had switched over to metric like they said they were going to when I was in grade school. It is base 10 not 12 and it is just so much easier.

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pushthatbolder
Yes i know that. I was just stating it to support my post.. i know how measurement and numbers work

The issue with your drawing conversions has to do with how drawing programs deal with measurements. They are based in an abstract way as "units" and those units are set in preferences and displayed accordingly. They typically aren't converted and need to be re-scaled by a size ratio and simply not by changing the units in many cases.

As for the US not adopting the metric system, it had more to do with the associated costs more than anyone not being able to understand it.

... but it's a PITA too, when I'm repairing/refurbishing a bit older optical and laser equipment, where half of the screws and measures are imperial, the other half metric ... try to unscrew Allen screws with metric bits

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Some firmwares even support printing in inches, so if you find that convenient, do it. Fractional inches, of course; not 1 1/2", but 1.5".

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tmorris9
I am 50 and always worked in fractions and decimals. Since I got into 3D printing I am learning metric and I really, really wish the U.S. had switched over to metric like they said they were going to when I was in grade school.

I'm in the same age group, and had the good fortune of living near the Canadian border in the 1970's for grade school. Half of our TV came from Toronto, and half from Buffalo. I lived vicariously through Canada's metric conversion, and was really upset that the yardstick lobbyists squashed the USA metric conversion just as it was kicking off. I vividly remember their weather forecasts in the various media having both temperatures for about a year while everyone adjusted, and then the imperial temperatures were gone. I really wish that we did the conversion with them.

Oh, FWIW, the only non-metric parts on my printer are some 1/2-inch spherical magnets, which were used only because 10mm ones weren't readily available stateside at the time.....

I'm sure there are beneficial reasons for USA still using inches. However for the original question why does reprap use mm? I think it is a matter of people in numbers. Especially because that is how the opensource reprap project is designed to run. More people understand metric. It makes sense from a prospective of a collaboration that involves communities throughout the entire metric world. This could be one of the reasons the USA fab@home project never took off.


The real fact is that reprap as popular as it is does not have enough people momentum to function if it only uses 1 country.

Also standardization of reprap firmware to use Gcode was brilliant. It allowed reprap to automatically gain understanding from the CNC/machinist world.

Anything that Reprap can do that makes it more aligned with what another agreed upon standard that a big group uses helps.

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elwood127
Sorry about the double post. I thought that I had deleted the first one. I guess not. Thanks for the replies. It sounds like it is time to conform or be cast out. Once again America is wrong thinking that it holds the high ground. That's why an earlier Mars mission inpacted the surface. One guy designing in mm's and another in inches. I'm going to buckle down and set Rhino up for mm's. Something new to learn and that's what it's all about.

No problem. I remember something going wrong majorly with a spaceshuttle because the calculations for a rubber ring in the fuel compartment had strength calculations done in inches while the actual ring was created by using inches or the other way around.

I'm happy to see more and more people adapting to mm's, not because I'm a fanboy, but it's already used a lot, and it's still strange that some things still aren't standard worldwide. Just like liters vs gallons, stones and pounds vs kilograms etc etc.

Maybe in a couple of years...

The Metric system has been widely adapted now, here you can see a list of countries that have officially adapted to the metric system:
[en.wikipedia.org]

In the long run, it's probably better (in terms of saving money) for the US to also convert at a point especially when we relate the use of separate systems in co-operations with technology, intercontinental markets and the availability of mechanical parts.

It's painful to let go of things we are used to, but sometimes, to move on, we have to let go of ideas that are dear to us.

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KingRahl
Metric is a base 10 system. Easy to calculate.

No, it's just easier for humans because we inherently understand decimal. A computer doesn't do integer, float, or decimal arithmetic in base 10 anyways. It's just the ending result that is converted back to what we understand, base 10.

The answer is simple honestly.

Certain industries adapted one system globaly.

metric = just about every machined or produced article. Even cars built in the US use metric threads/bolts/nuts.

Standard = tiles, plumbing, and certain agricultural equipment.

The world is a mishmosh. At least we are down to small variations that are at least defined. Go look at mpg on a vehicle in the UK and a vehicle in the US. Same car gets higher MPG, the reason? The MPG standard in the UK is different than US.

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That is because pints and gallons are different units in the US and UK even though they have the same name.

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KingRahl

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pushthatbolder
...I have tried importing using imperial and it makes the object 2.5 times bigger...

This is because there are 2.54 cm in 1 inch. The file was exported using a 1/1 scale.

Except that he was pointing out the difference between millimeters and inches, so the factor should have been 25.4, not 2.5.

I admit that when trying to grasp the size of something in my head, I do a mental calculation/estimation into inches. That's what happens when you use one particular system for over 50 years. However, I'm glad that were using the metric system here, and, to me at least, it's kind of embarrassing that America hasn't/can't adopt the metric system. It is a far superior system - at least that's what we were taught back in the 60's when we were being told that it was the future.

For everyone who wants to know what is what

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jaguarking11
The answer is simple honestly.

Certain industries adapted one system globaly.

metric = just about every machined or produced article. Even cars built in the US use metric threads/bolts/nuts.

Standard = tiles, plumbing, and certain agricultural equipment.

The world is a mishmosh. At least we are down to small variations that are at least defined. Go look at mpg on a vehicle in the UK and a vehicle in the US. Same car gets higher MPG, the reason? The MPG standard in the UK is different than US.

Uh I work in a very large machine shop and we program everything in decimal inch and every other shop I have worked at used decimal inch. Using metric fasteners does not mean the item was produced with a metric print. Anything we share with other countries is done with dual dimensions.

If you can't handle working with both units, you might not be cut out to be in manufacturing/engineering. It's pretty obvious when something is 1mm vs 1 inch...

Edited 1 time(s). Last edit at 02/26/2015 03:33PM by tjb1.

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I'm not trying to burst bubbles or burn bridges, but state facts.

quote 'Uh I work in a very large machine shop and we program everything in decimal inch and every other shop I have worked at used decimal inch. Using metric fasteners does not mean the item was produced with a metric print. Anything we share with other countries is done with dual dimensions.'


but not in a machine shop outside of usa right? the world is really really big if you think about it. in fact usa is only 318.9 million out of 6.916 billion people, and only Liberia, Myanmar and United States of America do not use metric. according to the new world encyclopedia, 95% of the population uses metric.

people [www.google.com]
[en.wikipedia.org]
[en.wikipedia.org]
[www.newworldencyclopedia.org]



This all being said, it is quite easy to have your settings in inches and as long as the settings are for the country used for, and the software is setup consistent and there is no questionable doubt inches are used it makes sense to use inches.

However when dealing with a project or a community web site where 95% concencus is to use metric, it makes for a lot fewer headaches if items made to the community in question are set to metric.

so for 3d printed items i stick with metric, for items i cnc and use in usa only. i stick with inches. only convert when absolutely needed and with great caution and double tripple checking, and then some more over a period of days. when your equipment can brake from calculation errors in acceleration speed, cut rate, overload,backlash, run-out, feedrate, jog speed, and spindle speed, it is aweful to convert!!

Edited 1 time(s). Last edit at 02/26/2015 04:26PM by jamesdanielv.

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tjb1
If you can't handle working with both units, you might not be cut out to be in manufacturing/engineering. It's pretty obvious when something is 1mm vs 1 inch...

Yeah, you'd think that...

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tjb1

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jaguarking11
The answer is simple honestly.

Certain industries adapted one system globaly.

metric = just about every machined or produced article. Even cars built in the US use metric threads/bolts/nuts.

Standard = tiles, plumbing, and certain agricultural equipment.

The world is a mishmosh. At least we are down to small variations that are at least defined. Go look at mpg on a vehicle in the UK and a vehicle in the US. Same car gets higher MPG, the reason? The MPG standard in the UK is different than US.

Uh I work in a very large machine shop and we program everything in decimal inch and every other shop I have worked at used decimal inch. Using metric fasteners does not mean the item was produced with a metric print. Anything we share with other countries is done with dual dimensions.

If you can't handle working with both units, you might not be cut out to be in manufacturing/engineering. It's pretty obvious when something is 1mm vs 1 inch...

Yeah, your a US based machining shop. The world does not beggin or end with the US. I Have lived in the US all of my life, I went from grade school to college here. I am perfectly capable of doing conversions. With that said, the machining shops around the world that use only metric far outnumber the ones that do both or use only standard.

Personaly I am more adapt to doing things in metric than inches or fractions...... I was educated in the us with inches, feet etc. I own tools that are precise that measure in .001 inch, but at the end of the day my metric tools win out.

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Machine shops are dual units everywhere, even in metric countries.

Try getting metric bar stock - it pretty much does not exist. In many metric countries it is still very difficult to get metric tooling as well. Most cutting tools such as slitting saws, drills and unusual endmills are considerably cheaper and more common in imperial. Even if you think you are all metric, the chances are a taper or collet somewhere in the system is actually imperial.

Frankly it doesn't really matter to anyone in manufacturing because when someone gives you a print in mm/inch, the worst case is you click a box on the computer.

Its really only a problem when you are designing an assembly that is forced to mate both imperial and metric components. Every time I have a project that needs both metric and imperial fasteners I feel like punching someone in the face.

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tjb1
If you can't handle working with both units, you might not be cut out to be in manufacturing/engineering. It's pretty obvious when something is 1mm vs 1 inch...

Funny story. There's a local factory here that makes custom cardboard boxes as a job shop. (Here being the northeast USA.) They have had such a rough time finding qualified help to make boxes that they approached the state to help create a regional training center to make people more employable. The local paper had an aptitude test that nobody applying for work could pass, like "take a 12-inch square, trim 1/8-inch off of all four sides, and tell me what size the resulting square is?" People today are completely lost when they can't punch something into a calculator and have the answer spit out for them. Oh, and this company isn't paying french fry wages. Why teach people to use an archaic system when metric does it for you?

C'mon, even American drug dealers and gang members have gone metric! When was the last time that you ever heard a rapper brag about "cracking a 23/64" into a rival?????

Wow, that was a very interesting topic. Thanks for all of the input. I'm going to draw something in metric right now. Gotta start somewhere.

I don't have problems using either system or converting between the two...