For reasons not relevant here, I had to wake up a New Old Stock bottle of an eye drug dispensed as a suspension in a small bottle:
A few hours at 50 RPM and it’s all shook up.
Tag: Mini-lathe
Tweaking an LMS 5200 Mini-Lathe
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Umbrella Strut Splinting, Round Two
Two more umbrella struts snapped and required the same repair, but, having drained all the suitable snippets from the Box o’ Brass Cutoffs, some lathe work was in order:
Umbrella strut splint – cutting I used the carbide insert in the mistaken belief it’d be less grabby, then applied the cutoff tool.
Break the edges, slide splints over the ribs, slobber epoxy on the struts, slide splints into place, apply masking tape for a bit of compression & alignment, and let it cure:
Umbrella strut splint – curing Three down, five to go …
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Lathe-Turned Almond Butter
Pure almond butter comes with the somewhat stilted admonition “Must stir product. Oil separation occurs naturally.” I’d just opened a new jar and was busily (and laboriously) stirring when I realized we have the technology:
Lathe-turned Almond Butter I installed the chuck’s outside jaws to grab the jar lid.
About three hours at 50 rpm, the lathe’s slowest speed, did the trick. We now have the smoothest, creamiest, best-mixed almond butter ever.
In a month or so, I’ll chuck up an unopened jar to see how well it works without any manual intervention.
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T-shirt Shop Rags
Small wipes made from worn-out cotton t-shirts absorb most shop liquids, don’t overstay their welcome after short projects, and prevent the deep emotional attachment leaving swarf in the clothes washer. Scissors cutting gets tedious, so mooch a rotary cutter and slash away:
T-shirt shop rags Synthetic fabrics don’t work nearly as well as cotton, so pay attention to the labels.
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Shortening a 2MT-to-1MT Morse Taper Sleeve
The hulking 1/2 inch Jacobs chuck is grossly oversized for most of the holes I poke in things spinning in the lathe. I already have several smaller Jacobs chucks for the Sherline’s 1 MT spindle, so I got some Morse Taper Sleeve Adapters for the mini-lathe’s 2MT tailstock. They’re longer than the “short” 2MT dead center:
1MT to 2MT adapter – vs 2MT dead center Because they’re longer, the tailstock ram loses nearly an inch of travel it can’t afford.
So I hacksawed the taper just beyond the opening at the tang and faced off the ragged end:
1MT to 2MT adapter – facing The steady rest jaws don’t match the Morse taper angle, but they’re way better than assuming the nose of the Jacob chuck can hold such an ungainly affair.
The short 1MT taper on the drill chuck doesn’t extend to the opening: when it’s firmly pushed into the socket, there’s no simple way to eject it. So, drill a small hole for a pin punch to pop it out:
1MT to 2MT adapter – center drilling I hate hammering on tooling, which means I must eventually enlarge the hole to clear a 5 mm bolt, make a square-ish nut to fit inside the slot, and gimmick up a plug for the 1/4-20 socket in the 1MT taper (used by the Sherline mill drawbar). More work than I want to take on right now, but it’ll provide some Quality Shop Time.
If the truth be known, I also got a 3/8-16 thread to 2MT adapter for the mid-size Jacobs chuck seen in the pictures, thus eliminating the thread-to-1MT adapter and plugging the chuck directly into the tailstock. The 1MT adapter will come in handy for the least Jacobs chuck; although LMS has a 0JT-to-2MT adapter, the less I monkey with that tiny taper, the better off we’ll both be.
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Plotter Grit Wheel Bushings
As part of recommissioning the lathe tailstock, I made some bushings to adapt Dremel sanding
drumsbands to an 8 mm shaft (in imitation of the grit drive wheels on the HP plotter):
Plotter Y bushing – samples They’re not all the same because the lad who’s building the plotter got to turn out his own bushings. We think the knurled version, with a setscrew to lock it on the shaft, will work better than adhesive-bonding the drum to the bushing.
The overall process starts with a rough 1/2 inch aluminum rod. Skim-cut to get a concentric surface and face the end smooth:
Plotter Y bushing – facing Then knurl it:
Plotter Y bushing – knurling The skim cut makes the aluminum rod a loose fit inside the sanding band, but the knurling enlarges the diameter enough to make it a firm press fit and I think it’ll have enough traction to stay in place.
FWIW, the wheels in the LittleMachineShop knurling tool seem pretty bad: the central holes aren’t quite concentric with the cutting edge, the bores are a loose fit on the mounting screws, the wheels are much narrower than the slots they ride in, so they wobble uncontrollably. It’s not a fatal flaw, but they definitely produce a sub-par knurl.
Face off the front, cut the knurling down at each end, then part it off:
Plotter Y bushing – cutoff Clamp it in the Sherline mill, laser-spot the edges, set the origin in the middle, and center drill:
Plotter Y bushing – center drill Drill and tap for a teeny M3 setscrew:
Plotter Y bushing – tapping Clean out the chips, debur the hole, install the setscrew, and you’re half-done: do it again to get the second drive roller!
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Mini-Lathe Tailstock: Alignment
After dismantling the tailstock to apply the tweaks, it was grossly out of alignment, as seen from the top:
Tailstock – initial H offset Seen from the side, the tailstock center is way too high:
Tailstock – initial V offset No surprises there.
The object of the game is to make the tailstock bore collinear with the spindle bore in all four degrees of freedom:
- Front-back
- Up-down
- Yaw angle
- Pitch angle
The first step is to match those two points, then measure the angular error.
Loosen the (new!) screws holding the tailstock top & bottom castings together:
Tailstock – modified screws I set them snug enough to prevent casual motion and loose enough to allow adjustment with gentle taps from a plastic hammer. Tapping the top casting forward lined up the dead centers horizontally, leaving only the vertical alignment.
Then I clamped the tailstock’s bottom casting to the lathe bed:
Tailstock – clamp for shimming Loosening the screws a bit more let me tilt the top casting to the left and slide a brass shim between the two castings, adding just a little more height to the left side to move the tailstock center downward.
This could do any or all of:
- Correct a pre-existing pitch angle so everything is fine again
- Pitch the tailstock ram axis out of line with respect to the spindle axis
- Confuse the issue
I started with a 6 mil = 0.15 mm shim that didn’t quite do enough and a 16 mil = 0.4 mm shim was a bit too much. Pinching a brass shimstock snippet between the centers show how they match front-back and don’t match up-down, with the tailstock center now too low:
Tailstock – alignment too low Some back-and-forth fiddling showed a 10 mil = 0.25 mm sheet came out about right:
Tailstock – perfect point alignment With the two linear degrees of freedom accounted for, measure the yaw angle by comparing the position of the tailstock ram’s far end:
Tailstock – vertical angle measurement – 1 With its near end:
Tailstock – vertical angle measurement – 2 Note: measure the offset by sliding the tailstock along the ways, not by retracting the ram. Reassuringly, the ram slides out parallel to its axis.
Measure the pitch angle, similarly:
Tailstock – vertical angle measurement As it turns out, the far end of the ram is 5 mils down and front from its base near the tailstock. Over 1.5 inches of travel, 5 mils works out to 0.19°.
Although it’s a small angle, the huge Jacob chuck supplied with the lathe puts a typical drill 125 mm from where you see the tailstock dead center’s tip. In round numbers, the drill point will be 16 mils low-and-front, about 25 mils radially off-center, which agrees reasonably well with what I actually see:
Tailstock – misaligned drill chuck Because I don’t do much turning between centers, I retinkered the alignment to put a point held in the drill chuck on center. Deep hole drilling won’t work quite right, because the ram extends along those 0.19° angles, but it’s Good Enough for now. It’ll be much easier to correct the yaw misalignment than the height mismatch.
Those of you who read image metadata surely noticed the pix aren’t in ascending temporal order. Verily, this was an iterative process, with pix happening all along the way.
The Smell of Molten Projects in the Morning 