The metric system sucks
in [Physics]
|
Prev: connecting Poincare-Luminet Dodecahedral Space with AP-reverse concavity #380 Correcting Math
Next: Hiding random?
From: Andrew Usher on 14 Feb 2010 12:15 Matt wrote: > Notice that drill sizes, like electronic resistor values, are > generally not equally spaced. Standard resistor values are equally spaced (logarithmically); did you mean 'unlike'? > One is quite unlikely to say, "That > drill would make a larger hole than I need. I think I'll use a drill > one-tenth that size." True. We don't calculate like that, a drill size may as well be an arbitrary number, given that you know the hole size. > A typo in a power of ten may go unnoticed quite easily. If one omits > the conversion from yards to feet, the result is off by a factor of > three; possibly within the safety factor of the design. If one > improperly omits "kilo", the result is off by a factor of one > thousand; probably beyond the safety factor of the design. And indeed, one of the points in my essay (Sec. V) was that this has been responsible for many medical errors, usually confusing milligrams with micrograms. Andrew Usher
From: J. Clarke on 14 Feb 2010 13:21 jmfbahciv wrote: > J. Clarke wrote: >> jmfbahciv wrote: >>> J. Clarke wrote: >>>> jmfbahciv wrote: >>>>> Andrew Usher wrote: >>>>>> Bob Myers wrote: >>>>>> >>>>>>>> Drills already have interchangeable bits, >>>>>>> Ah, another person who's never seen the inside of >>>>>>> a machine shop... >>>>>> OK, perhaps I didn't use the right terminology; I used that >>>>>> which I am familiar. Nevertheless, my point stands that you >>>>>> don't normally need a different machine for each different size >>>>>> of drilling. >>>>> Now ask the question why that is so. >>>> I'm not sure I see the point of this particular discussion. Most >>>> drills have three-jaw chucks that don't really require much of the >>>> drill bit other than that it be round and not so big that it won't >>>> fit in the hole or so small that the jaws won't close on it >>>> (typically about a 20:1 range). Certainly no drill press I have >>>> owned or worked with has had any trouble with bits that are >>>> fractional inch sizes, metric sizes, or sizes that are pretty much >>>> arbitrary. >>>> >>>> There are machines that require bits with tapered shanks or that >>>> use collets that require shanks of a specified dimension and form, >>>> or that require threaded shanks, but they are relatively rare--most >>>> drilling is done with the bits secured in a 3-jaw chuck and 3-jaw >>>> chucks are measurement-system agnostic. >>> The reason that 3-jaw chuck exists is to adapt to any system: US, si >>> or Sears. >> >> No, it's to let you use the same drill with a tiny little bit or a >> great big huge bit. The other option is to make the bit with a >> standard sized shank, which means that the bits will all have steps >> in them, which makes them more expensive to manufacture. >> >>>> Now if you're dealing with very small drills, circuit board drills, >>>> and the like, they do often have a standard shank diameter, mainly >>>> because their small diameter would make them difficult to handle >>>> otherwise (like you'd need tweezers and a magnifier to change bits) >>>> and there the measurement system does matter, but swapping out a >>>> collet takes seconds. >>>> >>> Thus, the specification of the drills included adapting to any size. >>> The reason for the generic is becuase there were more than one >>> flavor. >> >> Exercise--go down to Home Depot and look at the drill bits and think >> about what they would have to look like if 3-jaw chucks that could >> take any size were not in widespread use. Note that there are very >> small ones and very big ones and ones in between. Then think about >> how such a thing would be made. Then think about why anybody in his >> right mind would make them that way if there was another option. >> Then tell us whether you still think that the existence of 3-jaw >> chucks has anything to do with metric vs inch. >> >> You usually come across as a very sensible person but on this >> particular issue you're way off base. >> >> > I'm thinking about how drills changed over the years _before_ > electricity. I don't remember ever seeing hand drills with > the option of changing the bits. Do you know the ones I'm > talking about? You held the shaft with both hands and rotated; > the shaft looked like a step-function graph. Carpenters's brace-and-bit, which used a square taper shank. So happens that the two-jaw chuck for those was developed about the same time as the three-jaw chuck for round bits in the late 1800s. Prior to that time a square hole was used for the square taper shanks and collets for the round bits. Neither had anything to do with the introduction of the metric system. Just as an example, a starter set of drill bits for someone taking up machining in the US will have 115 bits ranging in diameter from 0.04" up to 0.5". Any drill that will take all those bits will also take any metric bit from 1mm to 12.5mm. Drills smaller than 1/4 inch or so with square tapered shanks are rare--you won't find any in such a set no matter how old it is. What you will find is a round taper, called a Morse taper, that was developed in the US in the 1860s and is now subject of an ISO standard and still in widespread use. The taper can be used directly to mount tooling, but more commonly is used to mount a chuck. Further, the fact that a country is metric doesn't mean that all drill bits used for machining come in even fractions of a millimeter. For example to get a close clearance fit on a shaft that is 10mm +/- .0001, you'd need to a hole that is between 10.013 and 10.055 mm diameter, or nominally 10.034mm. This is the nature of drilling and the reason that drills can take bits of many sizes. By the way, power drills were in use long before electricity--they ran on steam or water power.
From: Darwin123 on 14 Feb 2010 14:49 On Feb 13, 12:22 pm, Andrew Usher <k_over_hb...(a)yahoo.com> wrote: > I never said I do feel that way, only that most Americans that matter > do. > > Andrew Usher Down with the metric system and Jewish physics! Long live the English system and Aryan physics! The State must guide Americans along the spiritual path of God-given English units. By defending English units, Andrew Usher is doing the work of the Lord!
From: Michael Press on 14 Feb 2010 18:29 In article <ag9cn55qfj1i2knem4vfpisbitttp1jjlt(a)4ax.com>, Matt <30days(a)net.net> wrote: > On Tue, 09 Feb 2010 17:02:26 -0800, Michael Press wrote: > > >In article <joo1n55f1f4is2notocvi6elvku27ar5q9(a)4ax.com>, > > Matt <30days(a)net.net> wrote: > > > >> A (aqueous) chemistry lab is a cherry-picked environment for arguing > >> the merits of the metric system. The density of water is quite > >> important there. Not so much in a metallurgy lab. The density of iron > >> is expressed no more conveniently in metric (7.874 g/cm^3) than > >> English units (491.6 lb/ft^3). > > > >Everyone knows that only SI units > >are proper so that should be 7874 kg/m^3'. > > First, let's talk about those 'proper' SI units. > > Your preferred system of units seems to be meter-kilogram-seconds. > > Why is it the metric units are never systematized as > 'meter-gram-seconds' (mgs)? > > Because the 'gram' is too small. It was designed for the convenience > of table-top chemists in a wet chemistry lab. The gram is too small > for use in most of life. > > Even the chemists didn't want a mgs system, so they opted for a cgs > (centimeter-gram-seconds) system. They used the gram; but the meter > was too big for table-top chemistry, so they adopted the centimeter. > But the centimeter is too small for use in most of life. > > If the metric system is so well-conceived, where is the call for using > the meter-gram-second system > > > >Convenience has nothing to do with it. > > Huh?! > > Isn't that the primary argument for adopting the metric system: > because it is so much more convenient to use a decimalized system of > units? > > What is your case for using the metric system if not for convenience? > > > >We must sacrifice our comfort. > > Excuse me? For whom or what do you assert that we *must* sacrifice our > comfort? > > Would that not be a religious position? What god do you hope to > appease with this sacrifice? Try taking as contrary to my actual point of view everything I said in my 9 February message. Other messages of mine in this thread show that I use all widespread units of measure with equanimity and, in many cases, fondness. Ever notice how in a laboratory SI units must be prefixed with power of ten notation to get the numbers manageable? nm, GPa, Km, ug, ... Yes, you have. All units must be made human sized for everyday work. Those claiming that the metric system is the only rational system, then using this claim to demand that the USA go completely metric overlook the powers of ten prefixes. They have to be accounted for, and added in one's head to convert to SI units. This conversion is not trivial, and it is bothersome. I use strict SI units in all calculations. I convert from conventional units (nm, GPa, ev, foot, pound...) to SI, calculate, then convert back. It is the only sensible way. -- Michael Press
From: jmfbahciv on 15 Feb 2010 08:03
Matt wrote: > On Sun, 14 Feb 2010 09:23:15 -0500, jmfbahciv wrote: > >> J. Clarke wrote: >>> jmfbahciv wrote: >>>> J. Clarke wrote: >>>>> jmfbahciv wrote: >>>>>> Andrew Usher wrote: >>>>>>> Bob Myers wrote: >>>>>>> >>>>>>>>> Drills already have interchangeable bits, >>>>>>>> Ah, another person who's never seen the inside of >>>>>>>> a machine shop... >>>>>>> OK, perhaps I didn't use the right terminology; I used that which I >>>>>>> am familiar. Nevertheless, my point stands that you don't normally >>>>>>> need a different machine for each different size of drilling. >>>>>> Now ask the question why that is so. >>>>> I'm not sure I see the point of this particular discussion. Most >>>>> drills have three-jaw chucks that don't really require much of the >>>>> drill bit other than that it be round and not so big that it won't >>>>> fit in the hole or so small that the jaws won't close on it >>>>> (typically about a 20:1 range). Certainly no drill press I have >>>>> owned or worked with has had any trouble with bits that are >>>>> fractional inch sizes, metric sizes, or sizes that are pretty much >>>>> arbitrary. >>>>> >>>>> There are machines that require bits with tapered shanks or that use >>>>> collets that require shanks of a specified dimension and form, or >>>>> that require threaded shanks, but they are relatively rare--most >>>>> drilling is done with the bits secured in a 3-jaw chuck and 3-jaw >>>>> chucks are measurement-system agnostic. >>>> The reason that 3-jaw chuck exists is to adapt to any system: US, si >>>> or Sears. >>> No, it's to let you use the same drill with a tiny little bit or a great big >>> huge bit. The other option is to make the bit with a standard sized shank, >>> which means that the bits will all have steps in them, which makes them more >>> expensive to manufacture. >>> >>>>> Now if you're dealing with very small drills, circuit board drills, >>>>> and the like, they do often have a standard shank diameter, mainly >>>>> because their small diameter would make them difficult to handle >>>>> otherwise (like you'd need tweezers and a magnifier to change bits) >>>>> and there the measurement system does matter, but swapping out a >>>>> collet takes seconds. >>>>> >>>> Thus, the specification of the drills included adapting to any size. >>>> The reason for the generic is becuase there were more than one flavor. >>> Exercise--go down to Home Depot and look at the drill bits and think about >>> what they would have to look like if 3-jaw chucks that could take any size >>> were not in widespread use. Note that there are very small ones and very >>> big ones and ones in between. Then think about how such a thing would be >>> made. Then think about why anybody in his right mind would make them that >>> way if there was another option. Then tell us whether you still think that >>> the existence of 3-jaw chucks has anything to do with metric vs inch. >>> >>> You usually come across as a very sensible person but on this particular >>> issue you're way off base. >>> >>> >> I'm thinking about how drills changed over the years _before_ >> electricity. I don't remember ever seeing hand drills with >> the option of changing the bits. Do you know the ones I'm >> talking about? You held the shaft with both hands and rotated; >> the shaft looked like a step-function graph. > > Do you recall drills _before_ electricity? Why are they an issue? > > There are hand drills with 3-jaw chucks. > > You're talking about a "brace and bit." > http://en.wikipedia.org/wiki/Brace_(tool) > > You correctly used the work "bit" but confused it with "drill." OK. Thanks. > > Notice that drill sizes, like electronic resistor values, are > generally not equally spaced. One is quite unlikely to say, "That > drill would make a larger hole than I need. I think I'll use a drill > one-tenth that size." Now think about writing the description of that work. Assume your audience is people who grew up using cgs. > > The whole factor-of-ten thing in the pro-metric argument is about > convenience expressing orders of magnitude. It has little to do with > the magnitude of an adjustment one might make in the real world when > deciding how much of something to use for a particular application. Have you ever done the arithmetic by hand? Multiply 338000000 by 2100000. Which is easier on paper? > > Am I going to fill my gas tank with ten times the amount of fuel > because it is measured in metric units? No. If you are in Canada and fill your tank with 10 "gallons" of gas, you'll be surprised when you run out of gas. > > A typo in a power of ten may go unnoticed quite easily. It's easier to make an arithmetic error in my example. > If one omits > the conversion from yards to feet, the result is off by a factor of > three; possibly within the safety factor of the design. Off by 3' is not within many safety factors. > If one > improperly omits "kilo", the result is off by a factor of one > thousand; probably beyond the safety factor of the design. Which one would you notice first? The one that's off by 3' or the one that's off by a kilometer. /BAH |