Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Tag: Improvements
Making the world a better place, one piece at a time
I’m using good ol’ JB Weld steel-filled epoxy, rather than graphite / molybdenum disulfide loaded epoxy, mostly because:
I have it on the shelf
This is a non-sliding joint
My technique needs polishing, too
The key point: the tailstock is (astonishingly) well aligned and, if I can manage to not change how it sits on the lathe bed, this should be a zero-impact operation. Scraping / filing / fiddling with the high spots will change the alignment; I expect I must eventually do such things; this represents a first pass at the problem.
Applying a fat blue Sharpie to the tailstock ways:
Tailstock way repair – blue Sharpie
After sliding the tailstock back and forth a few times, the remaining blue shows where the ways did not make contact. Those shiny and silvery spots rubbed against the lathe bed ways.
The flat way looked like this:
Tailstock way repair – flat contacts
The patch along the upper-left edge and the small dot near the upper-right corner are the only contact points across the entire flat.
The outside of the V groove:
Tailstock way repair – outer V contacts
As nearly as I can tell, that’s actually a reasonably flat and well-aligned surface, with small contact points scattered all over. Granted, there’s a larger contact patch to the left and less to the right.
The inside of the V groove:
Tailstock way repair – inner V contacts
There’s a single point near the top left, another over on the right, and that’s about it.
I cleaned the tailstock ways with acetone to get rid of the Sharpie / grease / oil / whatever. Under normal circumstances you’d roughen the surface to give the epoxy something to grip, which definitely seemed akin to perfuming a lily.
To prevent permanently affixing the tailstock to the lathe, some folks put a generous layer of oil / graphite / soot / release agent on the lathe bed ways. I used some 3 mil = 0.08 mm Kapton tape, figuring an impervious layer would pretty much guarantee I could get the tailstock off again, no matter what.
So, we begin.
Butter up the tailstock ways with epoxy and smoosh into place atop the Kapton:
Tailstock way repair – V groove on tape
Make sure the tailstock remains well-seated where it should be:
Tailstock way repair – weights
Do other things for 24 hours while the epoxy cures, pry the tailstock loose by hammering The Giant Prying Screwdriver between the lathe bed and the underside of the tailstock (just right of the V-groove, where nothing slides on the bed, but I did use a bit of plastic as a shield), chip off excess epoxy, clean things up, etc, etc.
This time, I applied Sharpie to the lathe bed, then slid the tailstock back & forth a few times. As a result, the blue areas now show the contact patches and the gray areas just slid by without touching.
The flat way looks pretty good:
Tailstock way repair – flat epoxy blued
That round dot over on the right seems to be a steel protrusion; I think it’s part of the same lump appearing in the “before” picture above. That rather sharp point seems to have indented the tape and produced a low area in the epoxy around it, which may not matter much: it was the only contact point before I did this.
The V groove isn’t anywhere near perfect:
Tailstock way repair – V groove epoxy blued
On the upside, the ways have much, much larger contact patches spread across nearly their entire lengths, which isn’t to be sniffed at.
While reassembling the tailstock, I added a pair of M6 washers above the clamp plate so it cleared the bed with the screw tightened into the cam-lock post:
Tailstock clamp plate – washers
Which definitely calls for a small bushing, of course. If you put a lockwasher under the screw head, it won’t clear the end of the bed casting. So it goes.
Another washer under the ram lock screw changed the phase enough to keep the knob out of the way in both the fully locked and unlocked positions:
Tailstock ram lock – added washer
I slobbered some Mobil Vactra #2 Sticky Way Oil (thanks, Eks!) on the bed ways, snuggled the tailstock in place, and wow does that thing move! Verily, it slides smoothly and clamps solidly in place: a tremendous improvement over the status quo ante.
Some observations…
The tape (perhaps the adhesive layer) produces a slightly textured epoxy surface
The tailstock way’s small contact points indented the tape, even though it’s only 3 mil thick
Filling the low areas in the way works well
The high areas may not have enough epoxy for good durability
I expect the epoxy will wear faster than steel, so contact should improve with time
This is not a permanent fix
What I’ll do differently next time…
Apply more epoxy to avoid those small gaps along the edges
Use a real release agent: smoothed in place, it might provide a better finish. Might not matter
Verify a good prying spot before epoxying, say, the compound
All in all, though, this worked much better than I expected!
Mounting the ungainly WS2812 LED test fixture seemed like a Good Idea to keep the electricity out of the usual conductive litter:
WS2812 array test fixture – rear
The solid model shows more details:
LED Test Fixture – solid model
The power wires along the array edges slide into the rear (thinner) slot, with enough friction from a few gentle bends to hold the whole mess in place.
The knockoff Arduino Nano rests on the recessed ledge in the pit, with M2 screws and washers at the corners holding it down (the PCB’s built-in holes might work with 1 mm or 0-90 screws, but that’s just crazy talk). I soldered the power wires directly to the coaxial jack pins under the PCB; they snake out to the LEDs through the little trench. There should be another cutout around the USB connector for in-situ programming, although the existing code works fine.
The front (wider) slot holds a piece of translucent white acrylic to diffuse the light:
WS2812 array test fixture – front flash
It’s painfully bright: a few layers of neutral density filter would be appropriate for a desk toy.
The array runs hot enough at MaxPWM = 255 to produce a gentle upward breeze.
It looks even better without the flash:
WS2812 array test fixture – front dark
You’ll find many easier ways to get RGB LED panels, but that’s not the point here; I’m waiting for these things to die an unnatural death.
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After replacing the WS2812 LED in the 21HB5A socket, I drilled out the hole in the disk platter for a 3.5 mm stereo jack, wired a nice knurled metal plug onto the plate lead, and it’s all good:
21HB5A – Audio plug cable
The plug had a rather large cable entry that cried out for a touch of brass:
Audio plug – brass trim turning
Fancy plugs have a helical spring strain relief insert about the size & shape of that brass snout; might have to buy me some fancy plugs.
This time, I got the alignment right by clamping everything in the lathe while the epoxy cured:
Audio plug – brass trim gluing
I flipped the drill end-for-end, which was surely unnecessary.
It’s now sitting on the kitchen table, providing a bit of light during supper while I wait for a WS2812 controller failure. Again.
A length of aluminum hex bar became a nice 10-32 screw trimmer:
Screw cutting fixture – 10-32 – first cut
The hex neatly fits a 5/8 inch wrench, so I can tighten the jam nuts enough to run the lathe forward, part off the screw, and clean up the end just fine.
Unfortunately, the second test cut didn’t work nearly so well:
Screw cutting fixture – 10-32 – wrecked
With the cross-slide gib adjusted to the snug side of easy, the cut put enough pressure on the parting tool to lift the way on the tailstock side about 4 mil = 0.1 mm. The parting tool submarined under the cut, dislodged the fixture, and didn’t quite stall the motor while the chuck jaws ate into the aluminum.
Well, that was a learning experience.
After tightening the cross-slide gib to the far side of hard-to-turn:
Put a longer screw in the fixture
Grab it in the tailstock drill chuck
Crunch the hex end of the fixture in the spindle chuck
Remove the screw through the spindle (*)
Put a slight taper on the end of the fixture threads with a center drill
Deploy the live center to support the fixture
Like this:
Screw cutting fixture – 10-32 – rechucked
Turns out that angling the bit by 10° dramatically reduces chatter. If I had BR and BL turning tools, I’d be using them with the QCTP set to 0°, but they weren’t included in the set that came with the lathe.
It’s a good thing I’m not fussy about the diameter of that cylindrical section:
Which suggested the square version needed some softening:
LED Cable Clips – square – solid model
Apart from the base plate thickness, all the dimensions scale from the cable OD; I’ll be unsurprised to discover small cables don’t produce enough base area for good long-term foam tape adhesion. Maybe the base must have a minimum size or area?
I won’t replace the ones already on the saw, but these will look better on the next project…
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By and large, when you follow the recipe, you get the expected result:
Screw cutting fixture – M3x0.5 aluminum – side view
That’s another length of the same aluminum rod, this time with a full-length M3x0.5 thread down the middle, and a screw with a neatly trimmed end.
Running the lathe spindle in reverse prevents the screw from loosening the jam nuts on the left:
Screw cutting fixture – M3x0.5 aluminum – in lathe chuck
Running the spindle forward does move the screw enough to loosen the nuts. Perhaps I should put wrench flats on the big end of the fixture so I can really torque the nuts.
That front nut was mostly decorative, rather than tight, because I didn’t expect the first attempt to work nearly as well as it did. A bit of filing to taper the end of the thread and it was all good.
The Smell of Molten Projects in the Morning 