The Smell of Molten Projects in the Morning
Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Making the world a better place, one piece at a time
Epoxying a 100 kΩ thermistor to a 909 Ω resistor (because I have a bunch of them) serves as a simple heater tester:
It dissipates 450 mW, raising the temperature enough to let the PWM control kick in, but not enough to get scary hot.
Some heatstink tubing prevents reduces the likelihood of horrible accidents involving the 20 V motor / heater power supply:
Keeping it under 50 °C seems like a Good Idea:
Not that I have a need to heat anything, but the MOSFETs work!
Putting a small capacitor in series with the tuning fork resonator pulls the series resonant frequency upward and reduces the amplitude:
So something around 10 pF, net of stray capacitance and suchlike, should suffice. Plunk a small twiddlecap on the preamp board and tune for best picture:
Using the DDS generator as a manual signal source with 1.0 Hz step size shows the resonator tightens up the preamp’s response quite nicely:
I’m not convinced the preamp will have filter skirts that low farther away from the peak, but it’ll do for a start.
Zoom in on the peak with 0.1 Hz steps:
The bandwidth looks like 0.6 Hz, centered just slightly above 60.000 kHz, which should be fine for a first pass.
I’m tickled: all the hardware & firmware fell neatly into place to make those graphs possible!
Next step: install it in the attic and see whether the filter cuts back the RF clutter enough to stabilize the SDR’s AGC gain.
Hickory trees run on a triennial cycle and 2017 produced a huge crop of nuts. My trusty Vise-Grip makes short work of the otherwise impenetrable shells:
A nut pick extracts the good stuff:
In round numbers, you get twice as much shell as you do nut meat, so there’s plenty of shells left over.
I wrapped 10 ounces of shells in a double layer of aluminum foil, poked two rows of air holes along the package, dropped it holes-up atop the “flavorizer” bars in the propane barbie, and smoked 5 pounds of cured pork belly into some of the finest bacon we’ve ever eaten.
Heated and starved for air inside the aluminum wrapper, the shells became charcoal:
Yum!
Small wipes made from worn-out cotton t-shirts absorb most shop liquids, don’t overstay their welcome after short projects, and prevent the deep emotional attachment leaving swarf in the clothes washer. Scissors cutting gets tedious, so mooch a rotary cutter and slash away:
Synthetic fabrics don’t work nearly as well as cotton, so pay attention to the labels.
Breaking the fake heatsink off the big floodlight, drilling out the guts, and rebuilding it with a WS2812 RGBW LED left the PET braid too short for a nice curve from socket to bulb, so I swapped in a smaller and equally defunct PAR30 halogen spotlight:
And in green:
The white glass frit ring around the perimeter lights up nicely in the dark.
The knockoff Arduino Nano now runs the RGBW program, with Morse transmissions disabled and the white LED dialed back to MaxPWM = 32.
The hulking 1/2 inch Jacobs chuck is grossly oversized for most of the holes I poke in things spinning in the lathe. I already have several smaller Jacobs chucks for the Sherline’s 1 MT spindle, so I got some Morse Taper Sleeve Adapters for the mini-lathe’s 2MT tailstock. They’re longer than the “short” 2MT dead center:
Because they’re longer, the tailstock ram loses nearly an inch of travel it can’t afford.
So I hacksawed the taper just beyond the opening at the tang and faced off the ragged end:
The steady rest jaws don’t match the Morse taper angle, but they’re way better than assuming the nose of the Jacob chuck can hold such an ungainly affair.
The short 1MT taper on the drill chuck doesn’t extend to the opening: when it’s firmly pushed into the socket, there’s no simple way to eject it. So, drill a small hole for a pin punch to pop it out:
I hate hammering on tooling, which means I must eventually enlarge the hole to clear a 5 mm bolt, make a square-ish nut to fit inside the slot, and gimmick up a plug for the 1/4-20 socket in the 1MT taper (used by the Sherline mill drawbar). More work than I want to take on right now, but it’ll provide some Quality Shop Time.
If the truth be known, I also got a 3/8-16 thread to 2MT adapter for the mid-size Jacobs chuck seen in the pictures, thus eliminating the thread-to-1MT adapter and plugging the chuck directly into the tailstock. The 1MT adapter will come in handy for the least Jacobs chuck; although LMS has a 0JT-to-2MT adapter, the less I monkey with that tiny taper, the better off we’ll both be.
After dismantling the tailstock to apply the tweaks, it was grossly out of alignment, as seen from the top:
Seen from the side, the tailstock center is way too high:
No surprises there.
The object of the game is to make the tailstock bore collinear with the spindle bore in all four degrees of freedom:
The first step is to match those two points, then measure the angular error.
Loosen the (new!) screws holding the tailstock top & bottom castings together:
I set them snug enough to prevent casual motion and loose enough to allow adjustment with gentle taps from a plastic hammer. Tapping the top casting forward lined up the dead centers horizontally, leaving only the vertical alignment.
Then I clamped the tailstock’s bottom casting to the lathe bed:
Loosening the screws a bit more let me tilt the top casting to the left and slide a brass shim between the two castings, adding just a little more height to the left side to move the tailstock center downward.
This could do any or all of:
I started with a 6 mil = 0.15 mm shim that didn’t quite do enough and a 16 mil = 0.4 mm shim was a bit too much. Pinching a brass shimstock snippet between the centers show how they match front-back and don’t match up-down, with the tailstock center now too low:
Some back-and-forth fiddling showed a 10 mil = 0.25 mm sheet came out about right:
With the two linear degrees of freedom accounted for, measure the yaw angle by comparing the position of the tailstock ram’s far end:
With its near end:
Note: measure the offset by sliding the tailstock along the ways, not by retracting the ram. Reassuringly, the ram slides out parallel to its axis.
Measure the pitch angle, similarly:
As it turns out, the far end of the ram is 5 mils down and front from its base near the tailstock. Over 1.5 inches of travel, 5 mils works out to 0.19°.
Although it’s a small angle, the huge Jacob chuck supplied with the lathe puts a typical drill 125 mm from where you see the tailstock dead center’s tip. In round numbers, the drill point will be 16 mils low-and-front, about 25 mils radially off-center, which agrees reasonably well with what I actually see:
Because I don’t do much turning between centers, I retinkered the alignment to put a point held in the drill chuck on center. Deep hole drilling won’t work quite right, because the ram extends along those 0.19° angles, but it’s Good Enough for now. It’ll be much easier to correct the yaw misalignment than the height mismatch.
Those of you who read image metadata surely noticed the pix aren’t in ascending temporal order. Verily, this was an iterative process, with pix happening all along the way.
The Smell of Molten Projects in the Morning 