Posts Tagged Sherline
Clamping the octal tube into the Sherline let me set the XY=0 origin to the center of the base with the laser dot (visible near the front):
Find the edges, touch off the half the 32.2 mm diameter, then align the drill at XY=0 directly over the exposed evacuation tip:
Make a very shallow cut to verify the alignment:
Just inside the scuffed ring from the drill, you can see the fractured ring where the original one-piece Bakelite spigot / key / post broke off.
Then extract the drill from the chuck, file more relief behind the cutting edges so they actually cut, re-chuck, and continue the mission:
Pick a nice Bakelite ring out of the drill:
And eventually you can see all the way to the glass envelope:
The (knockoff) Neopixel LED sits directly below the evacuation tip and is about the same diameter, so much of that enlarged opening will be in shadow. Despite that, the tube does seem noticeably brighter:
Drilling that tube was so harrowing that I can’t imagine similar surgery on an intact octal base.
Perhaps just slicing off the tip of the Bakelite spigot and gluing a single very bright red/orange LED in place, rather using than a (knockoff) Neopixel a few millimeters away, will suffice.
Or just give up, top-light these tubes, and move on?
One of the octal tubes in my collection has a broken spigot / key post that lets some light in through the bottom of the normally opaque Bakelite base:
Perhaps drilling out the base would let more light pass around the evacuation tip, but that requires a shell drill to clear the tip. Some doodling suggested a drill with 12 mm OD and 8 mm ID, which was close enough to one of the smaller homebrew drills in my collection that I decided to see how it worked:
You (well, I) can’t freehand such a hole, particularly with a glass tip in the middle, so I needed a way to clamp the tube in either the drill press or the Sherline. A pad for the clamp screw in a V-block seemed appropriate:
The screw hole sits at the 1/3 point to put more pressure near the pin end of the base. Maybe that matters.
The setup looks like this, with a small red laser dot near the front of the base:
The tube rests on a random scrap of plastic, with the hope that the drill won’t apply enough pressure to break the glass envelope.
In normal use, the V-block would be oriented the other way to let you cross-drill the cylinder. In this end-on orientation, drilling torque can rotate the tube; compliant padding for more traction may be in order.
The OpenSCAD source code as a GitHub Gist now includes a module that spits out the clamp:
After drilling the platter for a Noval tube, I finally made a fixture to hold the platters firmly, but gently, in the proper position for drilling:
The platter sits more-or-less flush with the surface, where credit-card plastic pads work fine. Thinner platters may require compliant padding.
The solid model has locating pips at ±50 mm from the center and airspace below the platter for the drill bit:
The 1.16 inch hole spacing matches the Sherline’s tooling plate. The center hole seemed like a Good Idea, although it has no purpose right now.
The OpenSCAD source code is the same as before; just set
Layout = PlatterFixture; and it’ll produce the right thing.
Two of the external Li-Ion battery packs I’m using with the bike radios seemed to fail quickly after being charged, so I sawed them open to check the state of the cells. This time I used the fine-tooth cutoff blades, rather than a coarse slitting saw:
As before, a 2 mm depth-of-cut, done 0.25 mm per pass after the first millimeter, seems about right. I didn’t saw the front of the case near the jack, which proved to be a mistake; the interlocked case halves need cutting.
No cell trouble found, which leads me to suspect an intermittent short in the battery-to-radio cable that trips the battery protection circuit. The spare cables went into hiding during the shop cleanout, so I can’t swap in a known-good cable just yet; of course, the existing cable behaves perfectly on the bench. The suspect cable is now on my bike and, if the problem follows the cable, further surgery will be in order.
For the record, the insides look like this:
The cell label seems to show a 2004 date code:
Given that I got them on closeout in early 2010, it definitely isn’t 2014.
Unlike some of the other cheap batteries around here, they’ve been spectacularly successful!
The knockoff Neopixels measure just over 10 mm at their widest points, but some judicious filing rounded it off and brought it down to fit in the 3/8 inch = 0.375 = 9.52 mm hole I drilled in the hex:
I let it run for a day like that to make sure the thing wasn’t going to crap out, then epoxied everything in place. If the WS2812B controller fails, the repair will require drilling out all the electronics and wiring, then rebuilding it in place.
The fins come from the same HSS cutoff tool I used for the Bowl o’ Fire cap, cut at 2.5 mm intervals to produce 0.9 mm fins that IMO better suit the smaller diameter. I stopped cutting when the tool got through the hex flats to produce a continuous ring, cut the hex off a bit above the top fin, rounded the end with a carbide insert cutting tool, then sanded the flats to shine ’em up a bit:
It turns out that 12 inches of wire inside PET braid barely reaches from the cap to the Arduino Pro Mini in the base:
Next time, I’m going to add half a foot more wire than I think it can possibly require, with PET braid to suit.
A thin ring of clear epoxy holds the “heatsink” at the dead center of the bulb. It lights up a bit more than I expected, so opaque epoxy may be in order:
It’s still too big to suit even the big 21HB5A tubes, but brass definitely wins over plastic!
That blue PETG base has become the least-attractive part of the lamp, but it’s survivable for now.
Although I didn’t plan it like this, the shape of the first doodad on the mini-lathe reminded me that I really wanted something more presentable than the (now failed) ersatz Neopixel inside the ersatz heatsink atop that big incandescent bulb.
So, drill a hole in the side:
Epoxy a snippet of brass tubing from the Bottomless Bag o’ Cutoffs into the hole:
Recycle the old wire and PET loom, solder to another fake Neopixel, blob epoxy inside to anchor everything, and press it into place:
Cutting the failed LED & plastic heatsink off the wire left it a bit too short for that tall bulb, but some rummaging in the heap produced a 100 W incandescent floodlight with a nicely pebbled lens:
A thin ring of clear epoxy secures the ersatz heatsink to the floodlight:
This time, I paid more attention to centering it atop the General Electric logo ring in the middle of the lens, which you can just barely see around the perimeter of the aluminum fin. By pure raw good fortune, the cable ended up pointed in the general direction of the socket’s pull-chain ferrule; you can’t unscrew the bulb without tediously unsoldering the wires from connector atop the knockoff Pro Mini inside the base and squeezing them back out through the ferrule.
With the firmware set for a single fake Neopixel on pin A3 and a 75 ms update rate, the floodlight bowl fills with color:
It puts a colored ring on the ceiling and lights the whole room far more than you’d expect from 200 mW of RGB LEDs.
Pretty slick, even if I do say so myself …
The QC post and tool holders have very nice machining and surface finish; they evidently come from an entirely different production line than the lathe components. I can definitely get used to using carbide inserts, although I ordered some HSS inserts for interrupted cuts.
The HSS cutoff tool does what you’d expect:
The holes in the end came from short (“screw machine”) drill bits I got for the Sherline’s painfully limited Z axis travel. Even so, chucking one in the 1/2 inch capacity LMS drill chuck shows why a 16 inch bed isn’t excessive:
The 6 inch = 150 mm scale on the bed (to the right of the tailstock) extends to the limit of tailstock travel, so you could have another half foot of stock sticking out of the 3 jaw chuck. A collet in the spindle would give you another two inches, but it’s snug in there.
On the other paw, this is a little lathe intended to make little things. It’ll do fine…