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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

  • Mini-Lathe: DRO vs. Compound FAIL

    The Little Machine Shop 5200 lathe package includes DROs on the cross slide and compound cranks. The readouts report the position of the crank, not the slide position, which isn’t a major problem on a lathe.

    Unfortunately, the compound collides with the DRO on the cross slide:

    LMS Mini-lathe - compound vs DRO
    LMS Mini-lathe – compound vs DRO

    That is a major problem on a lathe.

    When you can’t turn the cross slide more than 45° from parallel with the bed, you cannot set the compound to the (typical) 29° degrees required for (traditional) thread cutting. That’s measured perpendicular to the bed, so it would be 61° on the compound rest scale, if the scale went that high:

    LMS Mini-lathe - compound way
    LMS Mini-lathe – compound way

    This mess doesn’t have a trivial fix, because the DRO body under the (non-removable) display doesn’t quite clear the compound screw:

    LMS Mini-lathe - compound vs DRO - bottom
    LMS Mini-lathe – compound vs DRO – bottom

    As nearly as I can tell, removing the entire DRO is the only way to slew the compound beyond 45°, but the DRO replaced the usual manual scale around the cross slide knob, so there’s no analog backup.

    The DRO mounts to the cross slide with three screws, so you can’t rotate it 90° to the side to get better clearance:

    LMS mini-lathe - DRO mounting screws
    LMS mini-lathe – DRO mounting screws

    The other four screws presumably mount the DRO encoder housing to the outer shell.

    The setscrew sticking up from the sleeve anchors it to the cross slide shaft. The slit milled into the shaft captures the end of the setscrew:

    LMS mini-lathe - cross slide leadscrew shaft
    LMS mini-lathe – cross slide leadscrew shaft

    The knob slides over the shaft, with a screw in the end holding it in place by friction against a split lockwasher; you can apply enough torque to turn the knob under the lockwasher in either direction.

    Removing the DRO doesn’t produce more cross slide travel, because the DRO body sits flush with the back side of that large disk.

    I think the cross slide knob collides with the compound DRO, but I put it all back together without any further exploration.

    Actual 6 inch DROs based on linear encoders seem to run $40-ish and other folks have fitted them to their mini-lathes. Verily, I don’t do much threadcutting, so I’ll just put this mess on the far back burner.

    That DRO ticks me off every time I look at it, though…

    Dumb design, no question about it.