Saturday, May 4, 2013

My Wife Says Nothing Is Scarier Than a Bored Predator

By which, she means our cat.  But bored engineers are dangerous, too.  I'm waiting, perhaps not sufficiently patiently, for the resin coat on the inside of the Sonotube to harden, before I suspend it by a rod through the interior, and do the exterior.  In the meantime, my wife had fallen asleep on the couch, so I couldn't turn on the TV.  What to do?

I had realized a couple of days back that there was some room to reduce weight on various accessories on the telescope.  For example, the mounting bracket for the finderscope was something that I put together myself, but it was a flat piece of aluminum 3/8" thick.  Lots of extra weight, and while it was not under any stress, a flat base against a round tube is less than optimal for stability.

So, I took that base and decided to mill it out to be a channel.  The legs on either side would, like the rods in my previous example, provide a very stable base against the tube.  (Yes, I should have used lower density acetal, either white to match the tube, or black to match the rest of the hardware on the tube, but I didn't have any pieces that were thin enough and long enough for this purpose.)

I don't use the vertical mill often enough to machine aluminum to remember: use a roughing mill for this.  Instead, I somewhat botched the first attempt, and barely saved the piece from becoming scrap.  You aren't going to see the bottom side of the channel -- it's functional but the milling marks and irregularities caused by my save are are way too apparent.  In addition, because the plate is now much thinner than before, the 8-32 screws that mount this plate to the rings that hold the finderscope were now too long for the holes, so I had to deepen the holes in the rings and re-tap the holes with more threads.  But I did knock two ounces off the weight!


  1. Trying again:

    WD-40 makes a great cutting fluid for aluminum, gives you a mirror finish.

  2. I have never tried that before. Perhaps I am spoiled by machining acetal, which is self-lubricating. I will give this a try.

  3. Just plain kerosene works pretty well, too. That was the cutting fluid of choice way back in the dark ages (when I worked summers in a machine shop.)

  4. A bored engineer. . .
    Is this perhaps how Bugatti autos came to be so @#$%^&* complicated compared to other luxury cars of their era?