Imperial vs. Metric

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Actually, it shows that seeming to follow rules while either not understanding them or applying them carelessly doesn't always get you the right result. Since it was a joke I assume that you did know what you were doing; I'm just saying if it's both a joke and a lesson then let's make it the right lesson.
That was something my Calculus teacher showed the class in 1975 to show how overlooking something seemingly hidden can be a problem... So it is a jokw and a lesson. I also remember years ago where all airlines are required to use Metric for fuel amounts due to anerror in units causing a plane to run out of fuel, something like 10000lbs fuel vs 10000kg, the pilot thought he was getting kg... got lbs...didn't look at the fuel gauges though...DOH!
 
I can tolerate Imperial when using machinist/engineer rules marked at 1/10th and 1/100th inch increments which allows the easy use of decimal places instead of fractions when specifying measurements and making them. It kinda' metricizes the Imperial system.
 
I can tolerate Imperial when using machinist/engineer rules marked at 1/10th and 1/100th inch increments which allows the easy use of decimal places instead of fractions when specifying measurements and making them. It kinda' metricizes the Imperial system.
Growing up, my dad (civil engineer) had one those triangle rules that confused me to no end. None of the markings made sense because they didn't line up with the ruler I used in class. Now that I'm older and have done some scale models, I couldn't live without my own engineers rule. I have a pair of digital calipers too and more often than not I use them in metric mode since the math is easier.
 
In normal life—well, depends on whether you think California is normal, I suppose—I use feet, inches, pounds and ounces. For instance, I have no idea what I weigh in kilograms or how tall I am in meters.

But from the very beginning, all of my products were designed solely in metric. Millimeters are a friendly scale for small products, and decimal math is just easier to work with in general.

I've gotten to where time-keeping and latitude/longitude have begun to bug me, too. I wish we used decimal math for those, too.

Internally, AltimeterThree stores time and GPS coordinates as simple integers, which are just as accurate and more compact than the normal minute/second or even floating point degree representation. I vote we put 32 bits each on latitude and longitude, and call it a day. That's 1 cm at worst precision at the equator, which should be fine.

See
https://www.xkcd.com/2170/
 
Is decimal really better than fractions? Well, let me ask you this: have you ever seen a digital caliper that reads to the nearest 64th (with fractions reduced, of course) so that you close the caliper on something, look at the LCD, and reads 2-13/32 or some such? It'd be easy enough to make. Ever seen one? No? Me neither.
 
Is decimal really better than fractions? Well, let me ask you this: have you ever seen a digital caliper that reads to the nearest 64th (with fractions reduced, of course) so that you close the caliper on something, look at the LCD, and reads 2-13/32 or some such? It'd be easy enough to make. Ever seen one? No? Me neither.
Yes, my Mitutoyo calipers can display in imperial decimal but when it hits a standard fraction, it displays the fraction instead. I think it'll display down to 64ths but it might only be 32nds or 16ths, I don't remember. I use them for woodworking mostly and I only measure down to the 16th. When I get home, I can get the exact model for you if you want.
 
OK, I stand corrected. I was thinking of one that displays only fractions, since that's all that old fashioned English users use, but I'll take this. What's the tolerance before it'll display as a fraction?
 
I haven't looked too closely but I think it's about +/- 0.0005. i.e. 0.0620 to 0.0630 will display 1/16" I have a Wixley digital height gauge on my planer that does similar but it displays the full decimal and if its a standard fraction, it'll display that too. I think all the Wixley digital measuring devices do it.
 
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Why does everything have to be "better" than something else. Each have their merits and neither are going away so cope, deal, or enjoy...the choice is yours.

It's not a matter of something having to be better or worse; Metric is just a better overall system. But to maintain both comes at a cost, one that I think is far too high. There have been lives lost, and major mistakes made, not including the additional costs involved in maintaining both. I learned Imperial then Canada switched to Metric in 1978ish, and now know and think in both. I believe it is way overdue that those who refuse to let go of the Imperial system do, for the greater good, and move forward.
 
Just today (and yesterday, actually) I ran into the same service update that used the goofy kgm f units. 10 kgm f was the torque. Now I have one of the latest, pretty darn expensive Snap On torque wrenches that has ft lbs, in lbs, NM, and degrees. However NO kgm f... If it was such a popular torque unit, you'd think Snap On would program it in... 72 ft lbs, by the way...
 
It's not a torque unit at all. It's an ill-advised (in many situations) force unit, the weight of a 1 kg mass, 9.81 N. Not a torque. That unit has nothing to do with metric vs. English units, it has to do with a bad servie bulletin.
 
It's not a matter of something having to be better or worse; Metric is just a better overall system. But to maintain both comes at a cost, one that I think is far too high. There have been lives lost, and major mistakes made, not including the additional costs involved in maintaining both. I learned Imperial then Canada switched to Metric in 1978ish, and now know and think in both. I believe it is way overdue that those who refuse to let go of the Imperial system do, for the greater good, and move forward.
It's not as easy as just switching for a lot of people. It's also a pain to find metric tooling at times compared to inch in the US. Not to mention a lot of metrology equipment, tooling, etc is in inch. That's a big investment to switch over. That said, for about 80% of the holes I need to make I just interpolate them with an end mill, so I don't need to have both metric and inch tooling on hand. Running parts designed in metric isn't as big of a deal to me as not working in inch.

I work with both daily and haven't had an issue. It's as easy to goof a conversion as it is to make an error adjusting cutter comp or setting work offsets. As long as you keep on top of it, it's not too bad. Though, I'm not a fan of getting drawings that have both metric and inch dimensions on them... :confused:
 
It's not a torque unit at all. It's an ill-advised (in many situations) force unit, the weight of a 1 kg mass, 9.81 N. Not a torque. That unit has nothing to do with metric vs. English units, it has to do with a bad servie bulletin.

kg-m is kilogram (force) meters. It is not a common measurement, but it has some currency.

gram-force, gram-weight, kg-force, kg-weight are all valid in context.

In the context rotary power systems (like an electric motor), kg-m may be a more immediately useful number than Nt-m, since the the unloaded torque will be figured in terms of the moment of inertia of the appliances or fixtures connect to the shaft, which number will be reported in kg-m^2.

If you are completing a Gage R & R on your torque tester -- by hanging an object of known weight from a known lever arm, for instance -- the easiest instrument to use for reproducibility validation will be a mass balance (a scale for measuring weight, but which reports mass). If the torque tester and the scale are in the same lab, the acceleration due to gravity may be taken to be the same for both instruments, and so a kg will exert the same force at the point of connection to the torque arm as it will on the force sensor of the scale.

If you can verify the linearity and resolution of the scale, you will not have to calibrate its force sensor for the Gage study -- so you won't need to know the value of gc they programmed in at the Ohaus factory.

edit: Expanded the "R' that is to be validated.
 
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We've reached a point where the only people still using SAE/Imperial are people restoring old cars, tractors, and industrial equipment. It's a legacy thing like COBOL, FORTRAN, or Netware. Dinosaurs. If you're not thinking in metric these days you must have one foot in the grave...both literally and professionally.

I had my periodic work physical for my job with the U.S. government recently. Measured me in feet and inches, weighed me in pounds and ounces.

Apparently America has one foot in the grave.

I'd like to add something else, but it would get me banned. Dick.
 
Units of mass and units of force are not the same thing. They are profoundly different. Mass is a measure of the quantity of matter, while force (or weight) is a push or pull. One kgm (mass) is the same both at sea level and, say, the surface of the moon, but the weight will be different. In all likelihood a kgf (force) will follow the same rules that I put forward on my previous post describing the lbm and the lbf in English units. Following that method the following can be written:

1 kgf = 1 kgm x 9.8 m/sec^2

Everything will follow accordingly. Note that a Newton (N or forgive me for saying nt) and kgf are both units of force, but they are not numerically the same. Since torque is force times length, one can convert from one set of units to a different set as long as they are careful.
 
Units of mass and units of force are not the same thing. They are profoundly different. Mass is a measure of the quantity of matter, while force (or weight) is a push or pull. One kgm (mass) is the same both at sea level and, say, the surface of the moon, but the weight will be different...

I wonder when they stopped teaching Helmert's equation to freshman physics students?

I am old, and my instructors were older than I am now when I took Physics 217/218 -- so I may be as much as a century behind the times, but still -- the acceleration due to gravity is a local thing. You can get away with 981 cm/s^2 most places, but once you get past that 4th significant digit, you are going to start making parts out-of-spec.

Kg-force is defined in terms of the standard acceleration due to gravity -- which is just a handy value to have so that your bathroom scale doesn't have to ship with a pendulum and a stop-watch.
 
kg-m is kilogram (force) meters. It is not a common measurement, but it has some currency.

gram-force, gram-weight, kg-force, kg-weight are all valid in context.
I was about to respond that this is quite right but off target, since I did not dispute that kgf (kilgram force) has its place; I called it "an ill-advised (in many situations) unit of force." What I called just wrong is kgf presented as a unit of torque. I was going to write that, then noticed that I'd misread the post about the service bulletin, and it actually said kgf-m (not the kg-m I was erroneously responding to) which is a torque after all. Perhaps a useful torque unit, now and then.
Resistance is futile...
Resistance is an electrical property of objects, and as such has no imperial unit in common use (and perhaps none at all) so I don't see what it has to do with this discussion. (Admit it, you asked for that one. ;))
 
It's not as easy as just switching for a lot of people. It's also a pain to find metric tooling at times compared to inch in the US. Not to mention a lot of metrology equipment, tooling, etc. is in inch. That's a big investment to switch over. That said, for about 80% of the holes I need to make I just interpolate them with an end mill, so I don't need to have both metric and inch tooling on hand. Running parts designed in metric isn't as big of a deal to me as not working in inch.

I work with both daily and haven't had an issue. It's as easy to goof a conversion as it is to make an error adjusting cutter comp or setting work offsets. As long as you keep on top of it, it's not too bad. Though, I'm not a fan of getting drawings that have both metric and inch dimensions on them... :confused:
I lived through it, so I know first hand that it's not easy. I will add that on top of being expensive, it is frustrating; at least it was for me for many, many years. However, it's doable and overdue.
 
My workshop, pieces/parts, tools, threads, scales, torque-measures, heck, even tiles on the floor are in feet/inches. When I see an Mx screw I throw it out! Too old to ever change (outside of motor nomenclature unfortunately); I even love Loki for keeping the 1/64th numbering system for nozzle throats! Down with decimals, long live fractions!

If the US was metric, Loki nozzles would surely be 6mm, 6.5mm, 7mm, 7.5mm, etc., and the motors would be designed around this.

Fractions are/were the bane of the vast majority---75% or more---of my (former) students. I'd bet that the percentage is a lot higher than that in the US population. Look at what happened when Hardees(?) came out with a 1/3 lb burger. It had to be abandoned because people were buying the 1/4 lb burger. It was cheaper, and you got more meat, because four is more than three...:rolleyes:

Best -- Terry
 
I just got a set of SAE/Metric hex keys from Sears in the "switchblade" package. They're held together with hex key fasteners, and the one on the metric set is a little loose... turns out that the screw is metric, so I don't have a hex key to tighten it unless I buy/borrow one. Gotta love it...
 
Resistance is futile... ;)
k-3t5v5wkvuTLe-xiYyEmrVXOwBMlHWAb44mtVR5VIY.png
 
I was about to respond that this is quite right but off target, since I did not dispute that kgf (kilgram force) has its place; I called it "an ill-advised (in many situations) unit of force." What I called just wrong is kgf presented as a unit of torque. I was going to write that, then noticed that I'd misread the post about the service bulletin, and it actually said kgf-m (not the kg-m I was erroneously responding to) which is a torque after all. Perhaps a useful torque unit, now and then.

So, to make me feel better; did I convert it correctly to ft lbs? One was 10 kgf-m and one was 8 kgf-m. I used 72 ft lbs and 58 ft lbs. The internet (which is never wrong... :rolleyes:) says 7.23 ft lbs to 1 kgf-m. Anyone have a different result?
 
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