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.

The New Hotness

  • HP 7475A Plotter: Ceramic-Tip Pen EOL

    Ceramic-tip plotter pens draw wonderfully crisp lines:

    Spirograph pattern - black ceramic pen - detail
    Spirograph pattern – black ceramic pen – detail

    Eventually, though, the fiber tip wears flush with the ceramic shell, becomes slightly indented, and ceases to make its mark in the world:

    HP 7475A Plotter - Ceramic pen - worn tip
    HP 7475A Plotter – Ceramic pen – worn tip

    As the lady says, “Starting from zero, got nothing to lose”, so I applied a fine diamond file around the tip:

    HP 7475A Plotter - Ceramic pen - filed tip
    HP 7475A Plotter – Ceramic pen – filed tip

    Well, all I can say is it seemed like a good idea at the time.

    Alas, even the newly exposed fiber didn’t make much of a mark on the paper and, as you’d expect, the ragged ceramic tip dragged painfully across the paper. I assume the fiber had filled with fossilized dry ink.

    A New Old Stock bag of fiber-tip pens emerged from the Big Box o’ Pens while I was flailing around:

    HP 7475A Plotter - NOS Green pen package
    HP 7475A Plotter – NOS Green pen package

    I think the “812” in the lower right corner is a date code, most likely early in 1988, so the pens started their lifetime countdown at least three decades ago. They still work, though:

    HP 7475A Plotter - NOS Green pens
    HP 7475A Plotter – NOS Green pens

    The plotter appeared at HV Open’s Mad Science Fair, because everybody loves a plotter!