Vacuum Tube LEDs: Grinding Off a 0D3 Base Spigot

Rummaging in the Hollow State Electronics box produced the shapely 0D3 regulator tube with an intact spigot / key post in its base:

0D3 voltage regulator tube in socket

0D3 voltage regulator tube in socket

Because the glass envelope (1.5 inch = 38.1 mm OD) extends beyond the base (1.125 inch = 28.6 mm OD), the simple base clamp must let the tube extend over the workbench:

0D3 Octal tube - V-block clamp

0D3 Octal tube – V-block clamp

There’s no way to clamp that mess in the Sherline, so, rather than freehanding the shell drill, I misused a Dremel slitting wheel to grind away the end of the spigot, which normally extends a bit beyond the pins so you can’t possibly insert the tube into the socket the wrong way:

0D3 Octal tube - ground-off spigot tip

0D3 Octal tube – ground-off spigot tip

The missing end exposed the hole in the middle of the post and showed this tube’s evacuation tip didn’t extend into the spigot. Emboldened by that, I continued the mission until the wheel wouldn’t reach any further:

0D3 Octal tube - Dremel grinding

0D3 Octal tube – Dremel grinding

That didn’t work well, but at least I didn’t break anything and nobody will ever see those mauled pin tips.

Obviously, the only way to do this right is to clamp the tube properly and mill the spigot flush with the socket; it’s time for more 3D printing…

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  1. #1 by Daniel B. Martin on 2016-10-03 - 08:01

    Having determined that the evacuation tip was not in the way, you might have used an ordinary drill bit to demolish the spigot.

    • #2 by Ed on 2016-10-03 - 08:36

      A peek into the future…

      The really nice thing about the Sherline is that the Joggy Thing produces well-controlled motion: I can mill downward at nose-pickin’ speeds without overshoot. The end mill also leaves a nice, flat surface when it’s done, although nobody will ever see it.

      Conversely, the bad thing about the Sherline is its limited Z-axis travel: there’s not enough height for the tube, a stubby 3/8 inch drill (*), and a chuck big enough to hold it.

      (*) Big enough to remove the spigot. The larger drills from the screw-machine set are way too long for anything other than the thinnest of flat sheet stock. [mutter]

      • #3 by madbodger on 2016-10-03 - 11:17

        How about a different stubby bit like a center drill or countersink? Alternatively, since you don’t care about the pins anyway, you could cut them shorter too. Extending that thought, you could just cut off the bottom of the base, pins and all, make a new tube holder that holds the outer diameter of the base, and have a large glass surface facing your LED(s).

  2. #4 by Vedran on 2016-10-03 - 08:39

    Clamp it to the lathe carriage or cross slide and use it as a horizontal mill (actually drill I guess)?

    • #5 by Ed on 2016-10-03 - 09:26

      That’s close to the spirit of the thing. I eventually conjured a V-block clamp for the Sherline, but it was still pretty scary.

      The top of the lathe cross slide is 57 mm below the headstock centerline. Conjuring a clamp to fit the QR toolpost would set me up for 4 inch diameter tubes, with an MT3 collet in the spindle grabbing the end mill.

      I don’t have any tubes that big, but a tall 5U4 full-wave rectifier on my desk right now probably won’t fit in the Sherline.

      Thanks for the suggestion!

  3. #6 by Hexley Ball on 2016-10-03 - 16:35

    Can you unsolder all the pins and remove the base of the tube? Then you could drill it out from the top, I suppose.

  4. #7 by jim oslislo on 2016-10-04 - 08:05

    I suppose it wouldn’t be as much fun, but you could saw it off with a fine jeweler’s saw between the pins and working your way around.

    • #8 by Ed on 2016-10-04 - 11:44

      I’m helplessly caught between “You’re wrecking priceless antiques!” and “It’s already junk, get over it!”.

      The bases have a certain charm to ’em, with fancy logos from long-dead corporations (*), and look much better than anything I could conjure, so I’m reluctant to destroy them to improve the light-from-below issue.

      More tinkering is in order…

      (*) The GE logo looks mighty familiar, though.

      • #9 by madbodger on 2016-10-04 - 12:34

        They are antiques, but many of them (TV types in particular, aside from sweep tubes) are generally common and unwanted. I’m still building vacuum tube gear myself, but I’m aware I’m in a minority. That 5U4 you mentioned is still popular for hi-fi and guitar amplifiers and some test equipment.