The 5mm Die, or Why I hate the metric system!!!

Last November I bought a lathe/mill combo machine tool from Grizzly tools. I know that it's Chinese made. Believe me, I would have far preferred to buy American, if an American company made such a thing, which to my knowledge, none does. The provenance of my tool is not the issue here and it's quality is adequate for my needs. No, what this post is about it is the little kit that I bought with my tool.

When making my purchase, I came across a little kit for a model Stirling engine. It seemed a perfect companion and a great first project. I've always had a soft spot for the Stirling and I figured it would be a good idea if I put something together first that I didn't have to trust me life too. That way I could hone my skills prior to building something that could potentially kill me (or at least horribly maim and disfigure me) if it malfunctioned. Only time would prove just how misguided my actions were that day.

The kit came in a box that was about a foot square and 4 inches deep. In actuality I later found out that the box was .35 X .35 X .1 meters, and would be my personal portal to the 2.54th level of hell.

Inside the box was a pamphlet that contained the drawings and the requisite legal mumbo with warning about how fire is hot and how tooled metal is sharp, etc. Pretty straight forward stuff. I had opened it the day I brought it home, before I had even set up the machine, glanced at the myriad tiny parts, and quickly put it somewhere safe and out of the way while I complete a few other projects.

Around the new year, most of the big things I was doing were done and as the winter was getting on in earnest, I decided to revisit the Stirling. I pulled off the shelf where it had lain dormant and took out the drawings. Having made the mistake of plunging heedlessly into things in the past, I figured I would be the height of prudence and familiarize myself with all of the drawings before taking all of the metal stock out of the shrink wrap that was keeping them contained. That was when I got my first shock. All of the measurements where in millimeters.

To most of you that may not seem like much. Give them an inch and they'll take a meter, you say? But when you're trying to put together precision components, like a shaft and bearing, especially one that needs to be air tight, the difference between 1/8" and 3mm might as well be measured in parsecs.

Now normally, switching between one system or the other is not a big deal. I'm familiar with metric measures from my studies of the physical sciences. Since academia is notoriously filled with Euro loving commie pinko milquetoasts, you'd be as likely to find a problem using yards, slugs and stone in a physics class as you would be of finding a shaved leg in a womyn's studies class. But the contents of my brain wasn't the issue, the calibration of my tools was.

How many cups in a liter? (It's 4.2267528377) If you had to measure out one liter of water, but your only tools were standard US measuring cups, how close would you get? If you're tolerance was +/- .3l you'd be in the clear. But what if you're tolerance what +/- .003l. That means you'd need to get in the range of 4.223 - 2.229. Think you could do it on you're first try? That was the problem I faced. All of my measuring equipment is marked in fractions of an inch. For outer cuts, no big deal. I can get down to a thousandth of an inch, about the width of a piece of hair (head hair that is, or a red carpet fiber if you catch my drift.) But tell me how you make a 3mm hole (+/- .05mm) without a 3mm drill bit? I'm serious, if you know, I'd love to hear it because I honestly don't know.

Now this could be the case where experience would conquer book learning, but I don't think so. There is no way to make such a precise hole that small without a tool exactly that size. So why don't I quit my belly aching and just buy some metric drill bits? I tried. I swear I did. But I ran out of time.

WTF?! you say. I read all that and there was no mention of a time constraint! And what about the 5mm die? Well this post has gone on too long, so for answers to these and other pressing questions, you'll have to wait until the next post.