Thursday, February 16, 2017

But Why Would You Want One?

If I ever mention to friends that I built a large CNC metal working machine, and that it's actually the third CNC piece I own, I inevitably get a question like that title.  What would you want one of those for?

While I'm not particularly interested in doing this, one guy from the Sherline CNC Yahoo Group posted a summary of a major project that's just a lot of fun to look at.  It's a model replica of a Terminator T800 arm and hand.
Lots of details the website, including more articles full of details on how he built it.

Not your cup of tea?  How about an Orrery?
As you can see, that's a screen capture from a 7-1/2 minute video by Ken Toons of his construction of an orrery of the planets known to the ancients - just out to Saturn.  Turn the handle and watch their relative motions. 

I've talked about using the machine to work on some 1911s or other guns, but it's not very financially smart to build a $2500 or $3000 machine to make one $1000 gun.  Perhaps more than that because parts seem to be expensive when bought this way.  But this is really more my speed.
Not sure where I got that.  It was just a picture on Pinterest.  Actually, I'd like to know where to get the fixture or plans to make one!

Of course, these things are pretty cool to me, too.  I posted this video back in 2015:

I call those "external combustion engines" because the flame is outside the cylinder and it just operates by inhaling hot air and letting it cool.   One of those might be happening.


  1. The answer should be either- "cool, I want one too!", or, "Great, what can we make now?!"
    Tools are such a part of my life, and my wife's life, and my friends lives, that I just don't have a clue what we would do without them. Around here, something breaks, or something needs making, it gets fixed or made, if we can. It is an immensely empowering feeling. Maybe one of the few things in life we can control.

  2. A Stirling Engine!

    I built one when I worked at Fermilab and had full access to the "Technician's Model Shop" where they let us tinker.

    I also built a lot of parts for my race car(s), but that's another story.

    The only "hard" part was getting the piston/cylinder clearance correct.

  3. Village Press publishes three magazines you might find interesting.

    I have not read the digital machinist, but I used to get the paper copy of Homeshop Machinist, and I still get the paper copy of Live Steam and Outdoor Railroading.

    Yesterday's copy of Live Steam had an article on converting small scale steam railroad block signal lights from incandescent to LED, and a continuing article on a small traction engine. The earlier traction engine articles discussed designing in CAD, and a lot of parts were cut on a computer driven plasma cutter table.

    The 80 percent 1911s seem to need a lot of hand fitting, and maybe an 80 percent Glock lower might be a good starter project.

    1. I originally started getting Digital Machinist a few years ago, and now get Home Shop Machinist too. They're both bimonthly, so I get one of them every month. Good magazines.

      The 80 percent 1911s seem to need a lot of hand fitting,... From what I read if I buy a custom 1911 from Wilson or Nighthawk Custom, they get a lot of custom fitting, too.

      I've looked at those 80% "Glock" lowers and considered them, but that's as far as I've gotten.

  4. Re: the fixture holding the handgun frame. In my youth (55 years ago) I worked in machine shops. I was never a "machinist", I did the job but I worked with machinist and I knew the difference. I would have need another 20 years at least to be a machinist and compete with these guys. Most were in their 60's and many were from Europe (oddly mostly Poland and Czechoslovakia). Some of the shops I worked in had a few drunks and wanna be's and some had lines of women working at a table full of assembly stations. But a few had these very smart, very capable old time machinists who worked 10 hour days and made things I never thought you could make. And they made these fixtures to allow a 'piece' to be mounted and machined and then remounted in a different position for subsequent machine processes. The jig alone was more complicated often then the piece. We had a number of old "Swiss screw machines" and the lesser Brown and Sharpe screw machines. These were run by cams and were the predecessors of the CNC machines you see today. A classic screw machine has a six position turret and a two position mount for a lathe tool that typically held a cutoff tool and sometimes also used a shaping tool. So basically they could control 8 operations using handmade cams designed specifically for the pieces to be made. Making the cams was an exercise in math and precision work. The Swiss machines could (or at least they claimed) could be used to a .0001 precision but consistently were a .001 precision. These machines "automatically" pumped out finished pieces from dawn to dusk day after day after day. Some of them made the same exact pieces the entire time I worked there. That was where these machines excelled because the setup time was so great.

  5. Why? See Chickenmom's Friday Night Steam post:
    All you need is some spare time, like 35,000 hours.

    1. Impressive!

      The time doesn't make sense, though. There's 2080 hours in a year of full time work, so no weekends, a couple of weeks off, 8 hour days. 35,000 is almost 17 years. If he worked 14 hour days, 7 days a week, that gets it down to about 7 years. Doesn't seem to add up.