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Archive for February, 2011

The Strange Joy of Making Chips

February 21, 2011 3 comments

MET 107 lecture today was a bit stressful, but  that was more my own psychological baggage than anything to do with the actual class.  Heck, I pulled a 92 on last week’s exam (#1 of 3), and I know what I did wrong on the questions I missed, so things are, touch wood, going well.

But it’s a crowded lecture, 48 students in a room that could comfortably hold about 40, and some days there’s a lot of noise and chatter.  There was today, so much so that Professor Anderson had to yell – literally, not figuratively – at everybody to quiet the hell down:

"OK, fellas, let’s get started.  Got a lot of stuff to get through today.  Settle down.  …  … HEY! THIS ISN’T A PAJAMA PARTY, IT’S COLLEGE, FOR CHRISSAKE!"

(shocked silence)

"In 15 years I’ve had to yell at a class three times, and now two of them have been you guys.  Work a little harder on impressing me.  You’re not paying thousands of dollars to listen to each other talk."

Now, I like Professor Anderson, and for the record I think he was entirely justified in taking this course of action.  (Indeed, in his position I’d probably have used much stronger language in a couple of places, and possibly opened with a gunshot into the ceiling, which is why I am not and should never be allowed to be a teacher.)  And his wrath had nothing to do with me – I wasn’t talking, because I’m 37 and frankly I got that shit out of my system in the ninth grade.  And yet, when that happened, I spent the next minute or so grappling internally with a powerful instinctive flight reaction.  I very, very much wanted, on some entirely anti-intellectual level, to just go home and lie down.

I guess that’s a scar from all those rancorous school board and town council meetings I had to cover.  I just cringe at the thought of being in the presence of authority conflict, even when I’m not in any way involved.  It was deeply – and surprisingly – uncomfortable, because so entirely irrational.  I was just sitting there waiting for class to start, and suddenly my lizard brain was going Flee, flee from this place, the gods are angry! Very disconcerting.

Anyway, once we got into the lab, things got better.  For one thing, there are only a dozen of us in the Monday afternoon lab session, and the room is much larger; for another, there was plenty to do, and Professor Anderson had regained his good humor, despite the absence of his tool crib guy and his regular TA (who had to go off to a doctor’s appointment, and did look like he felt truly dreadful).

So we went out and got to work, and after working on it for three weeks, I finished the last of my tool checkoffs, which means I’ve advanced to "novice machinist" and am no longer just some dude who wandered into the machine shop.

To be clear, they aren’t actually trying to make professional-grade machinists out of us in a single semester.  As mechanical engineering tech majors, we’re expected to end up designing things that the real machinists then have to make, so the idea is to give us some exposure to the machine shop environment and the capabilities of machine tools, so we’ll hopefully have that in the backs of our minds as we design things that may or may not be a royal pain in the ass for some other person to make.  So "novice machinist" is probably too generous; realistically, it’s more like "semicompetent dabbler".  But it does mean I’m not as likely to burn the place down or cut my own fingers off as a random civilian would be.  In theory.

In slightly more technical terms, I had to demonstrate a set of what marketing people would call "core competencies" on the four basic machine tools in what the University rather haughtily calls the laboratory: the pedestal grinder, the vertical mill, the engine lathe, and the band saw.  Once, and only once, those tasks were accomplished was I cleared to work on the actual parts required for my semester project – which I believe I now have seven weeks to make and get working with the rest of my team’s parts.  So no pressure there.

For those of you who are unfamiliar with machine tools, as indeed I was until recently, here is a quick rundown of what those four things are.  If you’re not interested in that kind of thing, that’s cool – come back in a day or two, I’ll be talking about CAD.

Now then.

The pedestal grinder – This is the machine tool people who’ve never been in a proper machine shop are most likely to have seen someplace, I suspect (with a couple of caveats I’ll get to below).  It’s just what it sounds like – an abrasive wheel attached to a big ol’ electric motor on a stand.  Actually, most pedestal grinders have two wheels, one on each side of the motor.  Waste not, want not, after all.  This apparatus can be useful for a number of things, but mainly what it’s used for is shaping smaller bits of metal into shapes suitably complex as to be hard to achieve on the other machines, and/or that don’t require a ton of really exacting precision.  For example, it’s possible to sharpen up drill bits and correct worn-out flathead screwdriver blades with it.  Or you can do what we did and actually make another tool, in our case a toolbit that is then used on the lathe.

All the animals in the machine shop are equal, but the pedestal grinder is a little more equal than the others in terms of how dangerous it is.  It does have a great heavy abrasive wheel spinning at some ridiculous number of revolutions per minute, after all, and if that should happen to, say, come off, you could be in for an exciting time.  In normal operation, though, it’s nothing to worry about as long as you don’t trip and fall face-first on it.  Unless you do what my dad did when he was around 25 and use one without eye protection, in which case you will never be allowed to accompany your son into a room with an MRI machine in it later in life.

The vertical mill – Also known as a "Bridgeport" after the most commonly known manufacturer.  Someone not familiar with machine tools, but knowing someone with a reasonably well-equipped garage, would see a Bridgeport and think, Damn, yo, that’s one big drill press.  And, in fact, that’s pretty much what a vertical mill is – a drill press with a college degree.  It can do a hell of a lot more than just drill holes, but the basic principle is the same.  What makes a vertical mill different is its adaptability.  It can be set up to run at a wide range of different speeds and equipped with a variety of different tools, and the table can be moved around in all three axes, often with power feed in at least two of them.  With that capability and the right tool mounted, you can trim a piece of metal to a precise size, put a nice finish on a part, put a chamfer on something – you can even drill a hole if you’re feeling really audacious.  Or cut threads into one you’ve already drilled.

The surprising thing about operating a vertical mill, from the standpoint of someone who had worked with drill presses before but never seen their bigger cousins, is how much stuff there is to keep track of.  For instance, what speed you run the machine at matters – a lot.  A home garage drill press is usually either on or off, but the RPM setting on a vertical mill is something that requires some foreknowledge and thought.  You need to know what the material you’re cutting is, what your cutting tool is made of, and the maximum cutting diameter you’re dealing with, at the very least.  Once you have all those things, if you have the appropriate tables handy or have memorized them, you can calculate the best speed, and then you look at the plate on the front of the machine to see how close you can get – and then you have to open it up and fool with the belts to set it up.  It’s all very old-school, and somehow strangely satisfying.

The engine lathe – This is another tool that looks something like something people with reasonably-well-equipped wood shops will be familiar with.  With a wood lathe you can make fancy table legs and whatnot.  A metalworking engine lathe works on the same principle, and looks similar, but – as with the metalworking equivalents of many woodworking tools – is a lot beefier and more complicated.  The basic principle is similar to the vertical mill’s, except sort of reversed and standing on its head – the workpiece rotates but is otherwise stationary, instead of the toolbit as in the mill, and the toolbit can move around relative to it on a complicated carriage mechanism.  You can face stock to a desired length, turn bits of it to different radii, drill a hole in the end of it – you could even make a fancy table leg if you wanted, though it would be pretty heavy.

The lathe is my favorite machine tool.  It’s also the one with the most complicated set of dials, levers, and buttons.  These two facts may not be entirely unconnected.  Once you’ve worked out the RPM setting (which is the same sort of thing as you have to do with a vertical mill), there’s also the feed setting to consider.  Again, there’s a reasonably complex little formula that involves looking stuff up on a table, particularly if you’re cutting outside threads, and then there’s another chart on the machine itself which tells you how to set the levers and dials for the feed gearbox to achieve the desired result.  This is a little like cracking a safe and invariably makes me feel like I’m starring in my own very short little caper movie.  Very satisfying.

The band saw – This is, well, a band saw.  Not really that exciting, except for the size of it: The horizontal band saw in our shop is about five feet long.  Cutting stock with it is a fairly straightforward procedure.  It doesn’t have speed settings or any futzing around with feeds; you just put the piece you’re trying to cut in it, make sure it’s properly supported if it’s too long to fit on the table, make sure you’ve put something in the other end of the vise to balance it if it’s too short to go all the way across, start it up and let gravity do the work.  Cleaning it up afterward is the hardest part, because it makes tiny little chips and they get all covered in cutting fluid.  Nasty.

So yeah, I’m enjoying MET 107, for the most part.  As previously noted it trips my hate-being-bad-at-stuff response quite often, but the instructor and his TA are patient and my checkoffs went well.  I got my first piece of for-real stock cut today, too, but ran out of time before I could do anything more to it than file off the burrs.

Now that I have my credentials on the tools, so to speak, I (slightly annoyingly) get to not use them for three weeks, because that was our last meeting before spring break.  I could go in for one of the evening sessions this week (probably Thursday) and try to get some stuff done; we’ll see.