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

  • New Cutting Board: Adding Feet

    So Kohl’s sent Mary a killer deal coupon and we bought some odds and ends, including a new cutting board to replace the decades-old one that I’ve been flycutting clean every few years. Evidently bamboo is the new Right Stuff for cutting boards; it’s certainly eyeshattering.

    The thing spent the last few days soaking up a slathering of canola oil, in the hope it won’t soak up other juices.

    Recess for cutting board foot
    Recess for cutting board foot

    The instructions say to store the board standing on end so it dries properly. Evidently you’re supposed to hang it from the ring screwed into one end, but a corresponding hook (not supplied) just doesn’t doesn’t have a place on our counter / cabinet / backsplash. However, we could stand it up, leaning against an under-cabinet shelf next to the toaster oven, if only it wouldn’t slide away.

    This calls for some aftermarket tweakage!

    So I hauled it to the Basement Laboratory Woodworking Wing and installed a pair of silicone rubber feet in little recesses.

    I grabbed a 7/16-inch end-cutting end mill in the drill press, because even the manual mill doesn’t have enough height for the board on end and the drill press doesn’t have enough reach for a Forstner bit without fiddling around with the emergency drop stopper clamp. The drill press does have a good vise and an XY table, so I got it pretty close to dead center on the third dark stripe from each edge.

    The feet are about 1/4 inch tall: I went down half that in the hopes they wouldn’t bump off quite so easily.

    Silicone foot in cutting board
    Silicone foot in cutting board

    But that didn’t quite work: the adhesive on the feet doesn’t grip the rather porous endgrain bamboo nearly well enough: a foot popped off after a day. I added a layer of Genuine 3M double-stick foam tape to the feet and that’s holding just fine.

  • Arduino Mega: Mounting Standoff and Screw

    The Arduino Mega has four, count them, four mounting holes in a more-or-less rectangular pattern around the edge of the board. Three of the four have enough room for standard pan-head 4-40 screws. The fourth hole is squeezed between two pin-header sockets, to the extent that no screw in my collection will fit.

    Screw on Arduino Mega board
    Screw on Arduino Mega board

    Having a lathe, however, makes this situation no big deal… and this time, I put the Sherline drill chuck in the 3-jaw because I wanted to, not because the 3-jaw was stuck. In truth, the lathe chuck simply won’t grab a 4-40 screw at all.

    Turning down the screw
    Turning down the screw

    I had that pointy right-cutting tool in the holder, so that’s how I cleared off the burr on the backside of the head.

    The chuck did grab the hex standoff just fine, though, and the final result looks like this…

    Modified standoff and screw for Arduino Mega
    Modified standoff and screw for Arduino Mega

    For future reference, the turned-down sections are 0.180 inch in diameter; call it 4.5 mm. The snout on the standoff must clear the pins,so it’s 0.100 inch or 2.5 mm long.

  • Pull Saw Blade Sheath

    Trimming some poster frame edges brought this useful tool out of hiding. It’s an ordinary Stanley 20-331 flush-cut flexible-blade pull saw that I’d used while installing laminate flooring in the kitchen & laundry room some years ago; it cuts the bottom of moulding like nothing else.

    Anyhow, what’s of interest here is the simple cardboard sheath I made to keep those delicate little teeth from getting bashed up in the tool drawer.

    Saw and sheath
    Saw and sheath

    Here’s a closer end view. It’s nothing more than two large sheets of thin cardboard (think cereal box or maybe consumer electronics box) separated by two narrow sheets. The blade’s thinner than any practical cardboard you’ll find, so just do it. It’s held together with yellow wood glue, because that’s what I had nearby when I built it.

    Saw sheath end view
    Saw sheath end view

    The note written on the sheath reminds both my shop assistant and me which way the cutting happens. Sometimes, we need all the help we can get.

    For what it’s worth, the new Stanley 20-331 listing shows a similar saw blade with a Fat Max handle. This is the older version, from back when thin was in.

  • Plastic Screw-top Flashlight Fix

    As part of my clear-off-the-workbench effort, this flashlight emerged from the dark depths. It’s a few decades old and wasn’t a good design: the “switch” is a simple contact between the end of the cell casing and the reflector rim, activated by screwing the reflector tighter on the case.

    Broken flashlight case
    Broken flashlight case

    The failure is simple: the case cracks through at the stress raiser formed where the “switch” contacts rest on a sharp inside corner. That stiff little spring maintains pressure on the cells, so the case is always under tension and eventually fractures.

    Flashlight clamped in mill
    Flashlight clamped in mill

    I grabbed the broken pieces in the lathe, turned off the fractured plastic, and wound up with a pair of nicely mating surfaces (and a somewhat shorter flashlight, but it’s still long enough). Apply enough Plastruct solvent glue to soften the new faces, then clamp them together. The big manual mill knows how to apply a strong, steady vertical force to a project like this.

    It’s once again hanging by the basement door, where it gets used roughly once every other blue moon (yeah, it’s color-coordinated). This isn’t the first time this flashlight has failed that way, but it’ll be the last: next time, it’s in the trash.

    Honest, I swear it!

  • Screwdriver Bit Ball Repair: Rubberdraulics!

    Went to use a small multi-bit screwdriver and the bit fell right out: evidently, the ball wasn’t swaged tightly enough; it and the spring went walkabout. Given that I don’t know when or where that might have happened, there’s no chance I’ll ever see those parts again.

    Screwdriver bit with missing ball
    Screwdriver bit with missing ball

    But I do have some 2 mm steel bearings that aren’t grossly oversized, so all hope is not lost. Alas, I have no idea what sort of spring to put in there, other than that I don’t have one of those.

    Drilled hole with ball
    Drilled hole with ball

    This looks like an application for rubberdraulics: use compliant silicone snot rubber as a spring. Lautard described a use with a lock ring and an external screw to apply pressure, but here it’ll work fine to allow a small motion for a tiny ball.

    Drill out the recess barely larger than the ball: the slight clearance allows the cured rubber to squish out around the ball. I clamped it in the Sherline vise and jogged into position by eyeball, then poked a hole with G83 down 1.5 mm. The original recess was a bit over 2 mm deep, so there’s plenty of room for the silicone in the bottom.

    Then mush some silicone into the hole, install the ball, push it down until it stands barely proud of the surface, scrape off the excess rubber, and let it cure overnight.

    New ball in place
    New ball in place

    There, now, that wasn’t so bad, was it?

  • Homebrew Mini-ITX LPT Bracket

    I’m putting together an Atom 510 box to replace the ancient Dell currently acting as the Sherline CNC controller, with the intent of seeing whether a rather anemic low-power CPU with two cores will work as well. The system board has room for one PCI card and I figured I’d install a second parallel printer while I had the hood up.

    But then I realized that the only LPT cards in my stash had tall brackets that wouldn’t fit in the new mini-ITX case.

    Well, it turns out that the LPT card itself would fit in the box, so all I had to do was reshape the bracket:

    • A bit of filing on the bottom knocked off a millimeter and put a tidy taper on the tab
    • A brief session with Mr Hammer bent the top flange over, so as to meet the case mounting flange
    • A somewhat surprised tin snips removed the excess length
    • A cylindrical file chewed out a somewhat generous screw clearance notch
    Finished LPT bracket
    Finished LPT bracket

    And then it’s just a matter of screwing things together.

    LPT Bracket - outside
    LPT Bracket – outside
    LPT Bracket - top
    LPT Bracket – top

    I’ll admit the clearance from the top mounting screw to the flange is terrifyingly cozy, but I’m not averse to applying force majeure to either an unsuspecting LPT connector or the case itself…

    The top view omits the screwdown clamp that secures the card to the case so you can see where the screw notch goes.

  • Door Stop Bumper Fix

    After slightly over half a century, the rubber bumpers on the doorstops around the house have stiffened up and, occasionally, one falls off.

    Although I suppose I should just buy a new doorstop, molding a dab of silicone snot around the end of the nice brass post takes only a few minutes (plus an overnight cure). If what they tell us about silicone adhesives is true, this one is good until the sun goes dark…

    Re-bumpered door stop
    Re-bumpered door stop

    Another no-CNC repair!