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Glowire, and Machining Under the Influence of the Cold

Posted by Tom Benedict on 08/01/2011

The errant kite order my wife and I placed several weeks ago finally came in.  Or rather, it’s been in for a while, but nobody told me.  Let me back up a little first:  We have a PO box that we use to get our mail.  There’s no home delivery where we live, it being a fairly rural setting and all, so this actually makes sense despite the fact that neither one of us is a scam artist.  It’s been hard convincing online and mail order vendors of this at times, but it’s true nonetheless.  In case you’ve never had a PO box, this is how it works:  If it’s mail, they  shove it in your box.  You open it with a key, remove your mail, close the box, and lock it.  If it’s a package, they stick a card in your box.  You take the card up to the desk, and they give you your package.  Sounds simple, right?

Most of the time it really is.  Card = Package.  If you order something, you start looking for your card.  Kites tend to come in long, thin boxes.  In postal terms this is called “Not Subtle”.  I think it’s also called “PITA” because every time I order kite stuff I get funny looks about the general shape of the thing.  It doesn’t conform to the Standard Box Formula they’ve developed, therefore its contents must be Suspect.

This time in addition to having three kites for my kids that might actually stand a chance of flying in the nutty winds we get in Waimea, it also contained the Glowire kit my wife got me for Christmas.  It’s like a cross between kite lights and Tron!  So you can understand I was eager to try them out as soon as they arrived.

They didn’t come in time for Christmas, and didn’t come before the new year, either.  Figures something cool like that would have to wait until my vacation was done and I was back at work.  Turns out I was right.  I went back to work on Monday, and drove up to the summit to work on one of our cameras that persists in losing vacuum.

The story of the camera is a long and twisted one, and one that to anyone other than another astronomical instrumentation specialist would be about as interesting as reading the US tax code after it had been used to wrap several thousand pounds of raw fish.  (Sorry, that’s boring AND gross.  My bad.)  Suffice it to say the camera has a vacuum leak, and it’s hard to find.  We came up with a plan that involved my making several parts in the shop in Waimea.

That evening I checked the post office.  No package.  Rats.

The next day I designed the new parts, found the material, worked out a cut strategy, and OH BABY!  I knew I’d make them on the big CNC mill in the shop.  I only recently started using the mill, and even then I’d only ever used the pre-canned cycles (means: stuff the mill will do itself, if you can describe the job.  Like making a hole.)  This time I was doing the full CAD/CAM/CNC process.  YAAAAY!

At lunch I checked the mail.  No package.  RATS!

The next day I started cutting metal.  Or so I thought.  One of my co-workers had the cold.  My daughter had the cold.  My son was getting sniffly, but by GOLLY I DID NOT HAVE THE COLD!  (Oh yeah I did…)  My first clue was when the tool plunged into the material, and the material started moving around!  I had clamped it down, but had never tightened the bolts on the clamps.  LOOSE PART!  I hit the emergency stop switch, swore silently to myself, and set it back up.

At lunch I checked the mail.  STILL no package.  GRRR…

With the material bolted to the table, things went a little better. I started boring out the central hole, and got ready to set the spindle speed and the feed rate.  You can tell how a machine is cutting by listening to it, and by looking at the chips coming off it.  Most of the time you can set it up so it hums along, removing metal cleanly, with nice thin firm chips of metal flying off.  Nothing I did seemed to help.  And the chips were getting bigger as it went.  Eventually I stopped the machine and realized the tool had been screwing itself into the material, pulling itself out of the collet that held it in the spindle.  Instead of cutting 0.100″ deep, it had ramped itself into the material until it was cutting almost half an inch at a time.  I re-seated the tool, ran it again, and this time it came out faster.  Finally I ground a flat on the tool, stuck it in a toolholder instead of a collet, and went at it again.  This time it worked.

I bored out the central hole using the pre-canned cycles, spotted my eight hole bolt hole circle, and got ready to face that side clean.  The part is 7.620″ across, so I figured if I faced an 8″ circle, I’d have a nice clean surface to indicate off off for the next step.  I entered everything in, and started it going.

I have to mention that this mill has a recirculating coolant system on it.  A jet squirts a continuous stream of coolant fluid on the rotating tool, and this coolant goes EVERYWHERE, winds up on everything, and drips constantly the entire time the thing is running.  About this time I came to the conclusion I really was coming down with the cold, and had made myself a nice cup of tea.  Between the trickle trickle trickle of the coolant dripping all over the mill and the bladder-inflating characteristics of the tea, I was dying.

It was a facing job.  The mill basically traces a cutting tool around in a spiral pattern until it’s machined off a circle of material.  In my case, 8″ diameter (or so I thought) and 0.005″ deep.  Surely it can run itself while I go to the bathroom.  SURELY.  Well…  I’m glad I saw where that was going, and stuck around.  The thing machined a wider and wider circle, until it looked like it could take a whole dinner plate in there.  That’s when I realized I’d put in an 8″ radius, not 8″ diameter.  It was going to happily machine the clamps right off the mill table.  I sighed, hit the E-stop again, and set things back up.

That evening I stopped off at the post office, and there was a card!!  A package!  My GLOWIRE!

No, it was a package for my daughter from one of her friends.  GRRR!

The next day I came in, this time with a massively sore throat and an utter and complete lack of sleep because I’d been hurking post nasal drip all night.  It was also my last day to make these parts, only one of which I had made any progress on.  I persevered.

The next step was an O-ring groove.  I used an undersized tool, cut the groove in two passes, and then used two cleanup passes to remove 0.003″ of material inboard and outboard of the groove.  Let the record state that aside from spotting the bolt hole circle, this was the ONLY part of the job that worked as planned.

The last step was to separate the part from the bulk material.  Before he retired, the master machinist we used to have on staff gave me this sage piece of advice:  Always hold onto the part you care about.  It sounds like such a simple idea, but so many home shop machinists, myself included, hold onto the bulk material and cut the part “free” as in “free to bounce around and encounter the cutting edge of the tool that cut it loose”.  Don’t.  I’d planned in room to get additional clamps in at this point, so I set them up and tightened them down this time.

By this time I was weaving around and my eyes were gummed up from the cold.  I knew I should’ve quit, but if I could get just this one part off, maybe the other people working on the camera would find the leak!  I ran the pattern.  It worked, but it barked like a sick dog the whole time!  Nothing I did with the spindle speeds or the feed rate made it better.  Little did I know the end mill I was using had a busted tooth, and that it was basically battering metal out of the way rather than cutting it cleanly.  It finished the pattern, and the part looked like a rough sand casting.  Every outside surface was dinged and pitted from the tool bouncing around.  I almost cried.  And at the very end the tool fractured and broke.  Then I really almost cried.

It takes a lot to bust a half inch carbide mill.  But apparently not so much that I didn’t pull it off anyway.  I stuck a new mill in and started making cleanup passes on the part.

Eventually it did clean up, just in time for me to realize I was beyond sick at this point and had to stop.  I cleaned up as best I could, brought the part in to give to the guy who was going to work on the leak, and got in my car to go home.  On the way I stopped at the post office one… last… time…

I had a card!  I also had a card saying some long/tall/weird package was going to be returned to sender if I didn’t pick it up.  I RAN to the window to get my kite box.  But I had to wonder why they were going to return it to sender after it had only been here for one day.  So I asked:

“Hey, I got this return notice.  Do you know how long the package has been here?  This is the first I’ve even seen a card for it.”

“Lemme see…  It’s been here since Monday.”


I would’ve stuck around to complain that I had never even known it was here, but I just wanted to get home and lie down in bed.  So I drove home, opened the box, pulled out my Glowire (and the kites for the kids) and promptly fell asleep.

It’s really no fair to get something cool like that, then be utterly unable to do anything with it.  Two of my kids have flown their kites.  I’m finally on the mend (though my chest feels like it’s full of steel wool), and now it’s raining.

Ah well…  There’s always the flu.

– Tom

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