Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
I carry a small camera with me at all times and find it invaluable for recording details and documenting events; now I never say “I wish I had a camera!”
This one is a Casio EX-Z850, which trades off nearly everything in favor of compact size. It has great battery life, enough resolution (the optics could be better), and manual controls (so it serves nicely as a microscope camera). It’s obsolete, of course, but you get the idea.
I have bigger & better cameras, but this one is always with me and that counts for nearly everything. The camera in a cellphone or PDA is not the same as a real camera.
Unfortunately, the thing has the griptivity of a bar of soap: all stylin’ metal and plastic. The black nubbly surfaces in the photo are my idea of a Good Thing: chunks of stair-tread tape providing enough traction that the camera no longer flies out of my hand with the greatest of ease.
Despite that, I always slip the lanyard over my wrist when I take it out of my pocket; often I do that before removing it from the case. That nervous tic saves me the cost of a new camera about twice a year.
If your camera fits into a desktop charging / USB cradle, as this one does, make sure you don’t stick the tape where the cradle fits against the camera. It’s really tough to peel off after the adhesive sets up…
Mary made that nice packcloth (she says “Cordura“) case, with a fuzzy fleece liner facing the LCD panel. The hook-and-loop closure is a tad noisy in quiet places, but it’s better than buttons or a zipper for this application.
I’ve learned to not keep tissues in the same pocket as the camera.
The number of daily visitors here rounds off to very nearly zero, so this spike from my Cabin Fever trip report stands out like a sore thumb:
Cabin Fever Trip Report Hits
The numbers are 118, 36, 10, 5, 4, 3. If you’re a geek, you’ll think of an exponential decay and it turns out that’s just about true: the time constant is 2.8 days and the equation pretty much works for the first four days, after which we’re into the Long Tail.
Most of the hits came directly from the EMC mailing list, with a substantial minority from Webbish sources like Gmail and various archives. There’s no way to tell how many people who subscribe to the list didn’t click on the link, although this provides a quick-and-dirty estimate of the folks interested in such things.
The counterweight gantry, laser aligner, and Y-axis bellows posts were also popular, at least to very small groups of people in the grand scheme of things. But if everybody showed up in the basement shop, I’d definitely have to move some stuff to make room!
After a while you realize that whacking the drawbolt to extract a tapered tool or collet can’t possibly be a Good Thing for the spindle bearings, particularly on the 10k rpm head. So you need one of these, a low-effort / low-skill version of the beauty described in Sherline’s Tip 15.
It’s basically a length of all-thread rod with a nut epoxied on the top, a nut soldered to a sleeve that locks to the spindle, and a brass tip epoxied on the bottom to push the taper out.
Drill a suitable hole in the nut for a steel rod, add heatshrink tubing on both sides so it doesn’t fall out. If you’re clever, you’ll make the rod short enough that it fits in your tool tray along with all the other itsy-bitsy tools and parts.
Bore out a steel cylinder to clear the top of the Sherline spindle and drill a small hole to exactly match the hole in the side of the spindle. Turn down the end of another nut to fit inside the cylinder and silver-solder them together. Maybe epoxy would work here, too.
Find or make a steel locking pin that fits the small holes, make a cute handle for it, press in place. Take some care that the handle radius clears the headstock pulley. It’s a very good idea to have a much better fitting pin than I started with; a too-small pin will goober the top edge of the spindle hole. Ask me how I know…
Turn the end of the all-thread down to a little post, drill a slightly larger hole in the brass tip which you turned to fit down the spindle bore, goosh together with epoxy. Hint: spin the cylinder on the all-thread before epoxying the tip in place.
To use:
Remove drawbolt
Spin cylinder up the all-thread a bit
Insert extractor in the spindle
Line up small holes, insert locking pin
Insert tommy bar in spindle
Turn the extractor handle & hold the tommy bar: don’t torque the locking pin!
Cup your hand under the cutter to catch it before it hits the part / table
… profit!
This goes a lot faster than it sounds and feels much nicer than beating the crap out of my precious Sherline head.
The far end of the Sherline Y-axis leadscrew isn’t supported, which really doesn’t matter much because the motors can’t drive the screws all that fast. But, if you’re like me, you think about dropping something heavy on the screw and maybe bending it just enough so it doesn’t work.
What to do?
Sherline Y-axis leadscrew bushing
The next time you replace the bellows covering the leadscrew, add a scrap of plastic with a suitable hole bored in it. Measure your leadscrew (metric & inch diameters differ!), poke a hole with enough clearance to make you happy, then cover one side of the block with double-stick tape.
Run the Y axis to about 30 mm from the far end, unbolt the motor mount, slide the table forward, put the bushing on the screw, slide the table back, affix the bushing to the column, screw the motor mount in place, and you’re done.
If you’re really fussy, make sure the bottom of the plastic block bears on the frame, but that’s in the nature of fine tuning.
This will cost you a bit of precious Y-axis travel, but the bellows need about that much space to fold up and you’re not losing much more than you already have.
The end of the X-axis leadscrew isn’t supported, either, but you can’t drop anything on it.
Sherline hot-rodders with super-fast high-torque nitro-breathing motors run the risk of bending the leadscrew by having it whip around, but that’s a whole ‘nother subject.
I use Cadsoft’s Eagle for schematics & circuit board layouts, then build the boards in my basement laboratory using Pulsar’s laser toner transfer and ferric-chloride etching. My Sherline CNC milling machine pokes the holes in the board, which means they actually wind up in the right places. I don’t mill the outline into any fancy shapes, generally using a tin snip and maybe a little filing; glass-fiber dust is a nuisance.
AXIS hole-drilling screenshot
My Eagle ulp routine (in the Useful Stuff page) extracts the holes from the circuit board layout, sorts by drill size, then visits each hole in nearest-neighbor order. It starts by touching each hole with a center drill, which probably isn’t necessary, but it makes me feel good and provides a last-minute check that everything is lined up properly.
Figuring the tool path is obviously the traveling-salesman problem in disguise, but a strict nearest-neighbor order is close enough for boards of this size. You could probably optimize it by brute-force exhaustion and that would be appropriate for production use, but I rarely make more than one version of each board.
Eagle’s standard part libraries use a weird set of hole diameters, which my routine rounds off to the nearest mil. I don’t have a vast array of drills, so I don’t pay much attention to the differences between, say, 0.024, 0.025, and 0.027 inch drills. Tool changes are strictly manual and I don’t have to change the drill if I don’t want to!
Got a bunch of teeny carbide drills as resharps from DrillBitCity a long time ago.
I double-stick-tape the board (center and corners) to a flycut sacrificial plate, which makes it flat enough for these purposes.The pic below shows a 60-mil board held down with masking tape; it’s the same layout as in the screen shot above.
Tool changes use a 2-inch block (plus a sheet of paper) as a height reference. You can tweak the ulp file for your setup.
My board layouts have a giant via at each corner, with the lower-left corner at (0,0). Drilling doesn’t require any fussy alignment, because I etch the board after drilling: the holes serve as bright lights to line up the pads & vias. I’ll have more to say about this elsewhere.
Speeds and feeds are on the sissy side; I crank the 10k rpm head up to a dangerous chattering whine and feed the drills at 5 inches/min (call it 125 mm/min). Both of those are far too slow, but work OK.
Run a shop vac to suck up the dust as you drill! I doubt that a typical shopvac filter removes the fines, but it’s better than letting all the dust settle on the mill and in my lungs.
Circuit board drilling
The clamps are these, mounted on studs screwed into the tooling plate.
Incidentally, the Sherline mill’s throat depth and Y-axis travel limits the board to about 4 inches along the Y axis; yes, with the spacer block installed. That’s just about exactly the maximum size the low-end version of Eagle can produce, so it’s a nice match.
There are other ways of doing PCBs. I haven’t tried trace-isolation milling, but PCB-Gcode looks like the ticket if you want to generate a breathtaking amount of glass-fiber dust. My quick check shows that it inserts semicolon-delimited comments into the tool-change commands, which EMC 2.2.8 promptly chokes upon, but that’s probably a quick configuration tweak and will change with EMC 2.3 anyway.
If you’ve got the scratch, there are commercial solutions: Chris Daniel (who was also at the Cabin Fever EMC booth) uses a T-Tech gantry router at work.
Memo to Self: Expect a call from a patent lawyer either telling me that I’m infringing somebody’s Nearest Neighbor Algorithm claims or asking me for my design notebooks to establish me as the Prior Artist.
I’d planned to whack the ends off the counterweight gantry I made for Cabin Fever Expo and mount them to a plywood plate, but I hate cutting stuff up. Turns out that the entire beam fit very nicely on the floor joists over the mill and the counterweight even hangs in a reasonable location.
Sherline counterweight gantry on ceiling
I used a plumb bob to get the pulley pretty close to the right location, then simply moved the beam around until the cable hung down through the middle of the hole. Securing it to two joists means it’s pretty nearly perfectly level along both axes, so the cable’s close enough to being vertical.
Of course, holding it overhead, aligning it, and then drilling the holes in the joists required three or four hands.
The blue doodad on the right end is the laser aligner on its new bracket. The crinkly silver tube is an exhaust duct for the never-sufficiently-to-be-damned radon mitigation air exchanger, a topic I refuse to discuss.
The observant reader will note that I still haven’t made dust shields for those open ball bearings.
I mentioned my cheap laser alignment gizmo for my Sherline milling machine at Cabin Fever and several folks wondered how I aligned the aligner. Having just mounted the counterweight gantry and bashed out a bracket for the pointer, here’s how it went down.
Laser pointer on bracket on counterweight gantry
The blue-gray bracket started life as a shelving support strut. I machined the web from between two holes so I could slide the pointer along the strut, filed off some sharp edges, and mounted the laser pointer with an assortment of machine screws & wing nuts.
I used a plumb bob to figure out roughly where the laser beam must start in order to go straight down the milling machine’s bore, then wiggled & jiggled the strut and pointer to get it more-or-less there. None of this is very precise, but it provides a starting point.
Here’s the trick: put a mirror flat on the mill table. When the reflected spot hits the bezel around the laser’s outbound lens, you know the beam is (pretty nearly) perpendicular to the table. Tweak the pointer’s mounting screws to make that come out right.
Use the plumb bob to figure out where the pointer is in relation to where it should be, wiggle & jiggle & slide everything until it’s there, then tighten & re-jigger everything to tweak the spot location.
Takes about 15 minutes, doesn’t involve any cussing, and works like a champ!
The Smell of Molten Projects in the Morning 