- A test build, a little crooked...
This is roughly what we're going for - this is a prototype and a bit "off" the desired result, but gives the big picture so to speak.
In the meanwhile, a reasonably experienced home-gamer machinist will mostly just need these pictures to know what's going on. The only trickery not shown here is the fact that I don't drill the
holes for the tungsten rods normal to the grid-end faces, but about 1 degree inwardly tilted to provide tension to hold the thing together. I couldn't find 19.5 mil drills...to press fit the rods (and 17.7 is too small and things break when forced) - only drills the same size as the rods, so...necessity, invention, all that.
- The stuff you need for this (other than the usual tools) Click to embiggen pix
The jig I use for drilling the rod holes on the lathe is a home-made special. Nothing that fancy. Here it's shown mounted on a piece of 1/2" hex stock I turned an end down to 1/4" to mount it so
I can rotate the thing in a chuck to get reasonably precise 60 degree angles. For things 200 is divisible by (the common stepper motor steps/turn) - the 1/4" bore lets me mount this to a stepper, driven by an arduino, and the whole mess clamped into the lathe chuck for drilling. But there's no way to get 200/8 to come out an integer, and micro-stepping is probably not going to be good enough for this.
Not that hex stock is perfect, but it's not bad either.
Here's a close up of the jig with some specs. The weird flange is not really a feature. When I went from 1" OD grids to 3/4 and everything got hugely better in all respects, I simply cut the end off the 1" jig I'd made and re-machined it to this size instead, figuring I wouldn't need the big one again. It made sense (good idea at the time?) to leave a little there as a reference for "flat" on the lathe chuck.
- Drilling jig detail
The setup to cut the tungsten rods to exact length without bending them etc is its own video, I'll get a still up here too, but it's a "hold your mouth right" kind of thing, better done in video.
- Overall jig. Block with cutout for setting stick-up.
This really is a much nicer drill press for little stuff than a Dremel and drill press stand...not cheap, but worth it. No shake at all in the quill bearings, no sensible runout either.
Here's a link to it on Amazon - currently sold out. It wasn't cheap...https://www.amazon.com/gp/product/B007FY0OQO
Run around 6k rpm for this with a diamond wheel selected for low runout itself...
- Where the diamond wheel meets the tungsten road.
You of course have to hold the part sticking up loosely with one hand while sliding the holding vise so that the rod slowly contacts the wheel - and with not much force, no worries, the wheel eats this easily.
