Posted on 11/05/2012 2:14:59 PM PST by null and void
Back in grade school, we were told that the Imperial System was a thing of the past, that eventually we’d be living the Metric System life, with all it’s base-10 logic built right in. We’d be just like the rest of the world. But those predictions have proven about as accurate as the flying cars and moon colonies that we all imagined we’d be enjoying in the year 2012.
Occasionally, the issue bubbles up and people argue back and forth about why we haven’t gone Metric, but I think it’s all about inertia. There would be a huge intellectual cost in moving to a new system—training ourselves to think of temperatures in Celsius when we’re leaving home and trying to decide on whether to grab a jacket. Straining to remember what kilometers per liter really comes down to, when we’re used to a lifetime of miles per gallon. Attempting to determine whether you’re losing enough weight, as you stare at the scale showing a strange number of kilograms.
While there are economic costs—heck, just think of the signage issues on our roads—they should be lower today than they would have been a generation ago. Many consumer products in this digital age already allow us to toggle between Imperial and Metric units. And the prevalence of smartphones means that no one has an excuse not to have a conversion app (or at least a calculator) on them at virtually all times.
What this issue comes down to is, as I said, inertia. It’s laziness. No one wants to be the generation that has to juggle two systems in their heads all the time. If we switched today, my kids would grow up pretty much thinking in Metric and would have no problem. But I feel like I’d forever be doing that calculation in my head. Even if I knew 28° C was a nice warm summer day, I think I’d always be converting it back to 82° F just to make sure I knew exactly how warm it was, based on my past experiences. We don’t want to be the ones straddling the two worlds, dealing with parts in both sizes or wondering how to deal with machinery that still had Imperial components that were no longer allowed to be manufactured.
Besides, who has the guts to push an idea like this forward in the country today? If Republicans championed the cause, Democrats would rail against it. And vice versa. And unfortunately, engineers, scientists and the like don’t have the kind of lobby that would be needed to get politicians interested. Even a public relations disaster like losing the Mars Climate Orbiter (due to a conversion mishap) didn’t move the needle on fully switching to Metric. So I guess I’ll just wait with you for that long-off day when we get the first flying car—and wonder what kind of miles per gallon that thing will get.
You get a lot of exercise jumping to conclusions. My machines are not CNC. Neither are my measuring tools.
OK, so you're in the "acceptance" camp rather than the "education" one.
You are in the "doesn't read" camp. Physics and Computer Science degrees aren't handed out by gas stations.
Would it help your understanding to know that my metalworking equipment is for hobby purposes?
No, I honestly can't think of why the units matter on a machine tool. Other than the scales printed on the controls, what is there about a lathe or milling machine that is dependent on the unit of measurement? ...especially if it's not CNC?
You are in the "doesn't read" camp. Physics and Computer Science degrees aren't handed out by gas stations.
Yes, I got that you have your degree. We're all very proud of you. Do you comprehend the meaning of the word "acceptance"? Are you claiming that you do accept the metric system and we are in agreement??? If not, then I think you're in the "acceptance" camp in your rejection of the metric system. You don't accept it, due to some other reason besides some inherent inferiority of metric.
Would it help your understanding to know that my metalworking equipment is for hobby purposes?
What happened to the very expensive machining equipment? I thought that's what we were discussing. Why can't your expensive machining equipment cut parts that are 10.0 mm in diameter? I don't get why they would need to be replaced in order to do metric.
Ah, this might be the sticking point. Sure, I can compute inch measurements for metric parts. But when I turn the knobs to the desired place, I will have to settle with the closest .001" and a wild guess for any .0001" of the computed result. It is common to guess the location of the .0005 position; and, the human eye can split things in half with remarkable accuracy. All bets are off if the final digits are something like .000146". So, the issue of making metric parts on English machines is NOT the arithmetic, it is turning the dials to unmarked positions.
If you had ever done any machining on a manual lathe or mill, you would know this. It is often essential for machine to be done to within .0001". That doesn't show up on machine dials, but surely does on micrometers. Those are expensive devils. In my humble shop, coming that close generally means using emory paper rather than the machine's tool point.
By the way, CNC machines are easily accurate to .0001", so they can handle the equivalences of metric measurements well enough. Still, many of those machines have position transducers made to English specifications; and, those babies are quite expensive.
Now here comes the most important problem: Machine power feeds. An Imperial lathe will cut threads based upon threads per inch. The only recourse for cutting metric threads using those lead screws is to use change gears at some multiple of 1:254, and the keep the carriage engaged for the return trip before cutting the next pass. That requires the machine to be stopped at the end of every pass, reversing the motor until the carriage is returned to the start point, and then once again reversing for the cutting pass. That is a lot slower than disengaging the power feed, hand cranking the carriage back to the start point, waiting for the threading dial to indicate the proper lead screw position, and then re-engaging the feed.
Correct. I'm no machinist. That was exactly the explanation I hoped for.
I couldn't think of any reason why the units would matter, and you have given me some. Thanks. :)
The go out an buy a small lathe and mill and start making stuff! ;-D
I found this to be a fun hobby, even if I make more scrap metal than ends up in the projects.
I will eventually make some firearms, including rifling the barrels ... but, I need to practice a whole lot more first.
Browse http://hobby-machinist.com/ if you want to see some talent. There is a fellow there who posted step-by-step pictures of his rifle build.
Jeep.
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