I think the sliding fit between the two ceramic blocks laps itself into a more perfect joint, to the extent it’s wrung together and can’t be moved. Even after filtering, our town-supplied water apperently has enough micro-fine grit for the purpose.
You’d (well, I’d) like to know the population infection rate, but we don’t have enough random testing to justify a number. Current testing remains biased toward those most likely to be infected, so the 15% cumulative rate (total positive / total tested) is certainly a gross overestimate and the 4% daily rate (new positive today / tested today) is still biased upward..
We figure the real population rate is well under 4%, which means we don’t encounter many infected folks out there.
A number of state are now “opening up” without worrying about the details. Because exponential growth starts very slowly and the dying begins three weeks after the infections, the CNN charts (near the bottom of the page) will be revealing; we’ll witness several large-scale epidemiology experiments in real time over the next few months.
I think if any single action other than a virus killed 100,000 US citizens in three months, there wouldn’t be nearly as much discussion about the correct response. On the other paw, COVID-19 still runs a little under the rate for heart disease, so it seems we can get used to dying, even in bulk, when we do it long enough.
Shooting the modified copper elbow with gloss black atop gray primer definitely improved its disposition:
I’d have been more inclined to apply several light coats if the wind weren’t blowing up a storm. As it was, I shot enough black to cover the not-quite-dry primer (“top coat at any time”) and called it a day.
The scuffed tubes aren’t quite that ugly in person, but they have suffered some abuse along the way. Seen from a normal working distance, however, it’s all good:
The lamp isn’t quite as tippy as I feared, so I’ll try it without the broken truck spring counterweight until something untoward happens.
Chuck up a length of 5/8 inch aluminum tube, clean up the end, and poke a thread runout slot into it:
Turn the soon-to-be-thread OD to 14.7 mm, well under the minimum 14.794 mm major thread diameter. I figure it’s better to match the existing not-quite-standard tube threads than to get all fussy about tolerances:
Drill out the tube to 27/64 inch = 0.422 inch = 10.7 mm, a bit larger than the OEM fittings, to easily pass the JST-SM connector I added so I could take the lamp apart:
Yeah, you’re not supposed to let the swarf build up like that, but it’s hard to stop when you’re getting good chip.
The compound is at 90° to the cross slide, because the DRO housing doesn’t let the compound swivel to the proper angle for thread cutting. I’m just ramming the threader straight into the tube, taking sissy cuts, and hoping for the best.
Kiss the OD with the cutter, set the cross slide DRO to zero, position the cutter just off the end of the tube, close the split nuts around the leadscrew, engage the threading dial at a conspicuous mark:
The first real pass looked good:
The runout slot is 1/16 inch = 1.6 mm wide and I’m running the lathe dead slow, so there’s plenty of time to punch the STOP button as the cutter enters the slot and let the spindle coast down. Flip the switch to REVERSE, crank the cross slide out a turn (1 mm with 0.3 mm of crank backlash), run the cutter back to the starting point, crank the cross slide in, and iterate until the fitting screws into one of the OEM lamp tubes:
The 5/8 inch tube is just a smidge too small for the copper fitting, so knurl the fitting to enlarge the OD slightly more than a smidge:
Break the knurl edges, part off the fitting, clean up the new end, and do it all over again:
The knurls got filed down to an exact slip fit in the copper elbow and will eventually be epoxied in place.
The cut-off tube on the lamp head also needs internal threads, so bore out the interior to flatten the weld seam:
No pix of the threading, but you have the general idea; the tube wall is a scant 0.6 mm thick, so this isn’t the place for full-spec threads. I stopped when the OEM tube screwed in place.
Apart from the hideous solder job, it came together pretty well:
It’s much more stable than Kapton-wrapped tubes jammed into a bare copper fitting, although that’s not saying much.
As received, the mini-lathe’s threading dial was misaligned by about 1/4 division, which is nearly halfway to the next engagement point midway between the divisions:
I added the red lacquer crayon while contemplating what to do, because I thought the dial was swaged onto the shaft. It turns out to be threaded, so I marked where the dial should be, grabbed the shaft in the (soft-jawed) bench vise, and twisted the dial with a Vise-Grip until it lined up:
Well, it’s closer than it was, OK?
There’s about that much slop on either side of the index line coming from the loose gear engaging the leadscrew, so that’s as good as it gets.