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.

Category: Machine Shop

Mechanical widgetry

Pin Spanner for 3.5 mm Audio Jack Nut

The external antenna jack on the Totally Featureless Clock is, by necessity, recessed way down in a hole (because I can’t get to the inside of the now-finished half-inch-thick case to gnaw it out from there). Perforce, that puts the locking nut out of reach.

Solution: a pin spanner wrench. I’m sure they’re available commercially, but what’s the fun in that?

The male threaded part of the jack is 0.230 inch OD, the nut is 0.313 OD, and the notches are 0.030 wide and 0.020 deep. Raw material is about two inches of 5/16-inch air-hardening drill rod, not that I’m actually going to heat treat it for this application.

Face off the end and drill the guts out with a 15/64-inch drill.

Drilling central recess

Grab it in the 3-jaw chuck bolted firmly to the table, then mill off anything that isn’t a pin. Don’t grab it in the milling vise, which doesn’t have enough oomph to hold a slick steel cylinder in place; don’t ask how I know this.

Milling pins in 3-jaw chuck

Set Z=0 at the top surface of the spanner-to-be and XY = 0 on the axis of the cylinder, of course.

Manual CNC, feeding the commands into EMC2’s MDI slot and then mouse-clicking the stored commands to avoid reduce typing errors. For my setup, Y=±0.171 to produce the 30-mil pin and X=±0.4 to clear on both sides.

After cutting the first side at 3 k RPM, feed 2 inches/min, and 10 mils per pass, I whacked the other side off in one giant 20-mil bite. I’m such a sissy…

A bit of heatshrink tubing improves the griptivity and it’s all good.

Finished spanner engaged in nut

This is the sort of thing you do once, drop in the baggie with the rest of the connector nuts, and use for years thereafter. I should’a done it years ago, but I’ve been able to not quite butcher the nuts with a needle-nose pliers…

[Update: It turns out a commercial nut driver was available, at least in one special shop in one special place, but no longer. For my delicate uses, that shaft into the jack isn’t really needed.]

2010-07-30
Sherline CNC Mill: Limited Headroom Thereof

Cramped Headroom

I had to drill a 1/4-inch hole in the Totally Featureless Clock’s case for the antenna jack. Fortunately, I have a 1/4-inch collet, because there was nowhere near enough room for the Jacobs chuck in there.

Removing the tooling plate wouldn’t help: the chuck setup needed another inch!

In truth, the headroom is rarely the limiting factor. Another inch or two of throat distance and maybe that much more Y travel would be nicer, while we’re at it.

Ah, well, it’s all a matter of tradeoffs. If the mill were much bigger, I’d just want to make bigger projects, right?

2010-07-29
IRQ Troubles on Razor
The Dell Dimension 4560, a.k.a. razor, that controls my Sherline CNC mill woke up without network support. That’s a showstopper, because all the G-Code files live on the server across the basement.

All my boxes have a network function dipstick test: the desktop background is an image on that same file server. When the NFS share wakes up dead, then the screen shows the default Ubuntu background: brown = down! (At least in Ubuntu 8.04 LTS, which is what EMC2 is built on right now.)

Checklist…
- NFS share isn’t mounted
- … and can’t be mounted
- ifconfig shows eth0 up & active
- can’t ping the server
- can’t ping razor from the server
- Link lights on network switch nailed to floor joist overhead are green
- Link light on NIC on back panel
- Activity lights on switch & NIC blink occasionally (??)
- Swapping ports on the switch = no change
- Laptop works fine plugged into switch = switch OK
So whatever is busted, is busted in the 4560. Drat!

(Should have checked cable between switch and NIC. Sometimes you get a data failure without affecting the link & activity lights. Weird, but stuff happens.)

Looking in dmesg shows that a bogus IRQ 11 occurred during startup:
```
[   44.439932] irq 11: nobody cared (try booting with the  irqpoll" option)
... time passes ...
... bad IRQ log dump gibberish ...
[   44.440440] Disabling IRQ #11
```
Fairly obviously, after that point nothing about the NIC or anything else on IRQ 11 will work: the hardware setup may be OK, you can write to it and read from it, but no actual data gets through.

A reboot didn’t cure the problem. Reboots in Linux rarely solve a problem; you’ve got to actually find the root cause and fix it, rather than shake the dice to see if a better combination comes up.

Anyhow.

Restarted to get into Dell’s attenuated BIOS configuration routine, changed the NIC to IRQ 3 (just because it was first on the list), saved, restarted, and everything works. The bogus interrupt is gone, the NIC is running, NFS shares are OK.

It absolutely beats me. But at least this is written down so the next time it happens, I’ll remember what I did.

Oh, yeah. The Sherline CNC mill uses stepping motors and uses cutters, so it’s a Steppin’ Razor, of course, and is therefore named razor. I suppose I could have called it molly, but that’d be a stretch.
2010-07-28
Cutting Thin Rings: Homebrew Punches

The Totally Featureless Clock is back for a refit: its preferred location turned out to have essentially no RF at all, so I must move the antenna out of the clock case on the end of a cable.

Drat!

I put the ferrite bar inside a length of PVC pipe, turned down to make it less ugly, with white plastic end plugs. Rather than fiddle around with complex mountings, I cushioned the fragile bar in closed-cell foam, which meant I needed some way to cut a bunch of foam rings.

Some rummaging produced a thinwall brass tube with about the same ID as the PVC pipe. A brief trip to the lathe put a reasonably sharp edge on one end.

Sharpening the brass tube

That edge is more keen than it looks; while it’s not razor-sharp, it’s plenty good enough. I didn’t use it as a punch, just grabbed it in a rag to cushion my palm and rotated it through the foam against a plywood scrap.

That produced a bunch of foam cookies.

Foam cutouts

The bar diameter was close enough to a standard hole punch that I didn’t have to make one. Centering by eye and rotating by hand turned the cookies into donuts.

Punched holes

And then they fit just fine…

Cushioned ferrite bar antenna

I made more donuts to swaddle the bar from end to end inside the PVC tube. I slipped the antenna in from the left, then pushed the donuts over the bar with Yet Another Brass Tube. The end result is an antenna compression-packed in foam, which ought to keep it in good condition through at least a minor oops.

Finished antenna housing

The screws pass through the end plugs to hold them against the pressure from the foam cookies at the bar ends. The holes are slightly counterbored on the top to blend the screw heads into the curve of the tube. There’s a 3/8-inch flat along the bottom that will eventually settle against the underside of a shelf.

2010-07-27
Useful, Albeit Incorrect, Sherline Wrench Sizes
My Sherline mill has inch sized fittings, but a couple of metric wrenches from the junk box reduced the workbench clutter …

Double open 10 + 11 mm:
- 10 mm = 10-32 nuts for step clamps (really 3/8 inch)
- 11 mm = small drawbar bolt (really 7/16 inch)
Combination 13 mm:
- 13 mm = large drawbar bolt (really 1/2 inch)
Now, I know full well that applying metric wrenches to inch fittings is a terrible idea, but y’know what? At the torque levels appropriate to Sherline fittings, they work just fine.

One of these days, I’ll be at a garage sale offering some double wrenches in the correct inch sizes …
2010-07-24
Epson R380 Printer: External Waste Ink Tank

Side cover latch and external tank hose

Having reset the waste ink counter on my Epson R380 printer, I finally got around to installing the external waste ink tank that will prevent the printer from drooling all over its innards.

Fortunately, rerouting the waste ink hose out of the printer doesn’t require the complete teardown mandated to remove the waste ink tank itself: you can do it by removing the cover, drilling a hole, moving the hose, and abandoning the tank in place.

The recommended way to remove the right-side side cover (as you face the printer) involves jamming a steel ruler into the “vent” (it’s actually a decorative feature) and shoving a latch out of the way. I trimmed a bit of stainless steel strip, shoved it in, and it worked fine. The cover latch is the complex central feature in the vertical gap between the case and the cover. The hose is routed out through a new hole down in the lower right corner.

With the cover off, it turns out that the “tank” is actually a “tray” (which is what it’s called in the maintenance manual) filled with absorbent fuzz. There’s no lid, so it appears they’re counting on evaporation to keep the total volume under control and surface tension on the fuzz to keep the ink from leaking when you tip the printer. I suspect if the printer spent a lot of time on its ear, though, things would get messy.

Internal tank and OEM hose

Removing the hose from the barbed fitting goes easier with a small screwdriver pushing it along; you (well, I) can’t just pull the hose off. It’s a very flexible silicone rubber (?) hose with an internal liner: very nice stuff.

The hose seems to drain only the head-cleaning station, not the long waste ink tank / tray across the width of the printer that catches overspray from borderless printing. That counter is at 5% of its rated maximum, so I’ll let it slide.

The ink, being adsorbed in the fuzz, won’t leak back out of the tray, so there’s no need to plug the barbed fitting.

Hole in case and rerouted hose

I used the 1/4-inch tip of a fat step drill to poke a hole at the very bottom of the plastic case, behind the pillar holding the white printer mechanism. The far end of the hose connects to a pump somewhere back in the bowels of the printer and that hole position freed up the longest amount of hose.

Much to my surprise, the tube wasn’t full of ink and didn’t bloosh blackness all over everything. Perhaps the hose drains back to the pump between head cleanings?

Then it’s just a matter of buttoning up the case, joining the hoses with the supplied barbed fitting, sticking the external tank’s hook-and-loop strip to the printer, and trimming the hose to fit. It Would Be Nice If the new tank hose were the same flexy silicone stuff as the OEM hose, but it looks to be ordinary Tygon-ish tubing and is a bit stiffer than I’d like.

External waste ink tank in place

No ink has reached the new hose yet, but I’m sure the next few head cleaning cycles will push out some oodge.

The tank vendor suggests “recycling” the waste ink by diluting it with black ink, but I’ll just discard it. Bulk ink isn’t all that expensive, compared to OEM ink cartridges, and I’d rather not borrow trouble.

2010-07-22
Cleaning Up a Pipe Center

I need this pipe center maybe twice a year and have hitherto managed to work around some nasty gouges and runout that came with it. But I finally cleaned it up by the simple expedient of dialing the compound to match the average angle (it was badly out of true) and skimming off enough to clear the surface.

The trick was realizing that the teeny little shoulder between the taper and the cone was concentric with both. I grabbed it tight (yeah, in a three-jaw chuck), took sissy cuts, and hit the end result with a file to smooth things out.

The remaining gouges are just fine by me.

Cleaned-up Pipe Center

It had been center-drilled in the small end, but the opening had taken a real beating at some point. Neither the live nor the dead center sat correctly and I couldn’t figure out how to hold the thing to re-drill the end.

2010-07-08