Tag: Mini-lathe

Tweaking an LMS 5200 Mini-Lathe

Garden Step2 Seat: Axle Repair
The cart in Mary’s Vassar Farm plot returned in need of repair:

$Garden Seat - fractured body$
Garden Seat – fractured body

Those fractures near the end of the axle let the axle erode the side wall:

Garden Seat – eroded body

This will obviously require some sort of reinforcement on the body holding the axle, but the first challenge involved getting the wheels off the axle:

Garden Seat – axle cover

Some brute force revealed the hub covers snapped over an install-only locking fastener:

Garden Seat – axle retaining clip

More brute force cut those fasteners (a.k.a. star-lock washers) to get the wheels off the axles.

While contemplating the situation, a box of 606 bearings (as used in the PolyDryer auto-rewind spindles) failed to scamper out of the way and produced a victim fitting perfectly on the 8 mm axle:

Garden Seat – bearing idea

I regard such happenstance as a message from the Universe showing I’m on the right track. The alert reader will note the axle should not rotate, but does sport scars showing it’s done some turning in the recent past, so the bearing may not be a completely Bad Idea™.

Finding a Lexan snippet exactly as thick as the bearing suggested bolting a plate across the side of the body to support the bearing, like this:

Garden Seat – reinforcing plate installed

Some layout work in LightBurn produced a template to mark the body for hand-drilling the holes:

Garden Seat – drill marking template

In retrospect, that was a mistake. I should have:
- Laser-cut an MDF sheet to make a drill jig
- Drilled one hole and inserted a screw
- Drilled the rest of the holes in exactly the right places
Instead, three of the holes in that nice Lexan sheet ended up slightly egg-shaped to adjust for mis-drilled holes in the body.

Lexan does not laser-cut well at all, so that sheet was drilled to suit after using the template to mark the holes:

Garden Seat – plate drilling

Then it got bandsawed / belt-sanded into shape.

I squeezed 5 mm rivnuts into whatever fiber-reinforced plastic they used for the body, which worked better than I expected. They’re intended for sheet metal, so I set the tool for 5 mm compression and they seem secure. I hope using plenty of screws across a large plate will diffuse the stress on each screw.

Then I threaded the axles and used acorn nuts:

Garden Seat – repaired axle installed

In this situation, I regard JB KwikWeld epoxy as “removable with some effort”, as opposed to the destruction required with those star-lock washers. High-strength Locktite might also be suitable, but I do not anticipate ever having to remove these again for any reason and do not want the nuts to fall off in the garden.

The re-replaced seat conjured from a cafeteria tray continues to work fine, as do its 3D printed hinges.

It’ll reside in the shed until Spring rolls around …
2025-12-05

Mini-lathe Change Gear Generator: Redux

Because the BOSL2 library includes a gear generator, I can now avoid creating a gear outline in Inkscape and importing it into my stacked change gear generator.

The labels now snuggle closer to the shaft and (barely) fit on smaller gears:

Mini-lathe stacked change gears - 28T - solid model — Mini-lathe stacked change gears – 28T – solid model

The stacked B-C gears for the jack shaft work as before, with both labels on the top gear:

Mini-lathe stacked change gears - 28-50T - solid model — Mini-lathe stacked change gears – 28-50T – solid model

The admittedly flimsy motivation for all this was to make a 28 tooth gear to cut a 0.9 mm pitch, thus filling an obvious hole in the gear table.

My collection of gears could do 21-60-81-50, but the 81 T gear collides with the screw holding the 21 T gear. Rearranging it to 21-50-81-60 showed the B-C gears exceeded the space available.

Because it’s all ratios and a 28 T gear is 4/3 bigger than 21 T, reducing the rest of the train by 3/4 should work. In fact, it produced a reasonable 28-80-81-50 chain:

Mini-lathe change gears - 28T installed — Mini-lathe change gears – 28T installed

The fact that I do not anticipate ever needing to cut a 0.9 mm pitch has nothing whatsoever to do with it; that gear will surely come in handy for something.

While I was at it, I made a 27 T gear, because 27 = 21 × 9/7:

Mini-lathe stacked change gears - 27T - PrusaSlicer preview — Mini-lathe stacked change gears – 27T – PrusaSlicer preview

You can never have enough change gears. Right?

The OpenSCAD source code as a GitHub Gist:

	// LMS Mini-Lathe
	// Change gears with stacking
	// Ed Nisley – KE4ZNU
	// 2020-05 use Inkscape SVG gears
	// 2025-12 use BOSL2 gear generator

	include <BOSL2/std.scad>
	include <BOSL2/gears.scad>

	/* [Gears] */

	TopGear = 0; // zero for single gear
	BottomGear = 28;

	/* [Hidden] */

	ThreadThick = 0.20;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	/* [Dimensions] */

	ShaftOD = 12.0;

	GearThick = 7.75;

	Keyway = [3.5,3.0,3*GearThick]; // x on radius, y on perim

	LegendEnable = (TopGear == 0 && BottomGear > 27) \|\| (TopGear > 27);

	LegendThick = 2*ThreadThick;
	LegendZ = (TopGear ? 2*GearThick : GearThick) – LegendThick;

	LegendSize = 5;
	LegendRecess = [8,6,LegendThick];
	LegendOffset = [0,LegendRecess.y/2 + ShaftOD/2 + HoleWindage,LegendZ + LegendRecess.z/2];



	//———————–
	// Build it!

	union() {

	difference() {

	union() {

	spur_gear(mod=1,teeth=BottomGear,thickness=GearThick,shaft_diam=ShaftOD + HoleWindage,anchor=BOTTOM);

	if (TopGear)
	spur_gear(mod=1,teeth=TopGear,thickness=2*GearThick,shaft_diam=ShaftOD + HoleWindage,anchor=BOTTOM);
	}

	right(ShaftOD/2)
	down(Protrusion)
	cube(Keyway,anchor=CENTER+BOTTOM);

	if (LegendEnable) {
	translate(LegendOffset)
	cube(LegendRecess + [0,0,Protrusion],anchor=CENTER);

	if (TopGear)
	zrot(180)
	translate(LegendOffset)
	cube(LegendRecess + [0,0,Protrusion],anchor=CENTER);
	}

	}

	if (LegendEnable)
	translate([0,0,LegendZ – Protrusion])
	linear_extrude(height=LegendThick + Protrusion,convexity=10) {
	translate([LegendOffset.x,LegendOffset.y])
	text(text=str(BottomGear),size=LegendSize,font="Arial:style:Bold",halign="center",valign="center");
	if (TopGear)
	zrot(180)
	translate([LegendOffset.x,LegendOffset.y])
	text(text=str(TopGear),size=LegendSize,font="Arial:style:Bold",halign="center",valign="center");
	}

	}

view raw Mini-lathe stacked change gears.scad hosted with ❤ by GitHub

2025-12-04

Mini-lathe Change Gear Banjo Shim

I intended to single-point a few turns on an 8 mm axle to ease running an M8-1.25 die over it, thus making a thread for a nut securing a wheel (about which, more later). This required selecting the change gears for a 1.25 mm thread pitch, the installation of which proved sufficiently awkward to give me the opportunity to discover a washer spacing the banjo just a little farther outward would improve the gear alignment:

Mini-lathe change gear banjo – shim detail

The overview shows how moving the whole banjo just a bit leftward better aligned black Gear B with respect to orange Gear A:

Mini-lathe change gear banjo – shim overview

From A to D, a 1.25 mm pitch uses 42 40 45 60 tooth gears. The 42 tooth gear supplies the magic required to convince a hard-inch 16 TPI leadscrew to produce good-enough metric pitches.

In addition to the usual hassle, the main reason the process took so long is doing having to do it twice. After I swapped Gear C and Gear B on the jockey shaft in the middle, the leadscrew produced the correct 1.25 mm motion for one turn of the chuck:

Mini-lathe change gear banjo – thread pitch check

Measure twice, cut once …

2025-12-03
Worm Bin Fly Trap

Despite freezing the kitchen scraps going into the worm bin since the previous fruit fly infestation, a zillion flies are now in residence. Lacking the peppermint-stick tube of yesteryear, I conjured another fly trap from common household items:

Worm Bin Fly Trap – overview

The gap around the top got a strip of tape after I took the picture.

The gallon jug has cardboard stiffeners supporting a sheet of the sticky paper I used for the onion fly traps:

Worm Bin Fly Trap – sticky paper holder

I was all set to 3D print a threaded adapter to join the two bottles when I realized they already had lids. A few minutes of lathe work added a passageway:

Worm Bin Fly Trap – Bottle caps

They’re held together by a generous ring of hot melt glue:

Worm Bin Fly Trap – lighting detail

The LED strip provides enough light to simultaneously attract the flies and repel the worms.

The laser cuttery looks like this:

Worm Bin Fly Trap – LightBurn parts

The white shape in the black block is a scan of the cut-open jug, with the other shapes in that row being rectangularized versions. The two tiny notches in the Top and Bottom shapes hold the sticky paper.

The two rings at the top adapt the LED-wrapped bottle to the existing fitting on the worm bin from the previous episode. They’re visible as shadows near the bottom of the bottle.

The circle is a laser-cut hole in the gallon jug bottom for the screened plug made for the pepermint-stick tube; the less said about that operation the better.

So far, so good, although previous experience suggests the flies will be breeding ahead of their (considerable) losses for the next few weeks.

2025-09-30
Champion Hose Nozzle: Refreshed Seal Attempt

The battered Champion hose nozzle came into play last fall, leaked profusely when turned off, went to a Safe Place for the winter, and recently emerged:

Champion hose nozzle – disassembled

The conical surface (to the right of the tip) must make perfect contact with the edge of a perfect cylindrical hole in the outer shell to shut off the water, which was obviously no longer happening.

There is no reason why that hole should still be concentric with the outside of the shell, but centering the latter in the four-jaw chuck put the hole within about 0.2 mm of where it should be:

Champion hose nozzle – lathe centering

I defined that to be Close Enough™ and made the hole smooth & concentric with a teeny boring bar and sissy cuts. A drill would likely have worked well enough, too.

Gently filing the nastiness off the cone showed it wouldn’t suffice, so center it while noting the irregular diameter all around:

Champion hose nozzle – lathe centering cone

A skim cut revealed the need for more attention:

Champion hose nozzle – scarred cone

Another tenth of a millimeter improved its disposition:

Champion hose nozzle – improved cone

Gentle touchup with a fine file reserved for special occasions may have been a further improvement:

Champion hose nozzle – finish filed

Add a dollop of silicone grease to encourage the shell to turn much more easily on the O-ring, reassemble in reverse order, and top it off with a new hose washer.

A quick test on a reasonably warm day showed the cone met the cylinder poorly enough to consign this nozzle to the brass recycling box.

It was fun trying, though …

2025-04-14
HQ Sixteen: Stylus Laser Ball Drilling
With the ball mount in hand:

HQ Sixteen – Stylus Laser – ball clamp test fit

The next step is to drill a 12 mm hole for the red-dot laser module right through the middle of the 1 inch = 25.4 mm polypropylene ball.

I decided to use a more-or-less standard laser module, rather than the Genuine Handi-Quilter laser, because:
- Cheap & readily available
- Identical spares on hand
- Two decades of red laser diode progress
Start by conjuring a lathe chuck fixture for a 1 inch ball from my OpenSCAD model and printing it in PETG-CF:

HQ Sixteen – Stylus Laser – center drilling

Run a few drills through the ball up to 15/32 inch = 0.469 inch = 11.9 mm:

HQ Sixteen – Stylus Laser – final drilling

Which looks terrifying and was no big deal.

The laser module didn’t quite fit until I peeled off the label, as setting up a boring bar seemed like too much hassle for too little gain. The ball is slick polypropylene and the laser module is chromed plastic, which means there’s not much friction involved and a stiff fit is a Good Thing™.

I did not realize the hazy white patches barely visible inside the ball were voids / bubbles:

HQ Sixteen – Stylus Laser – drilled ball

Next time I’ll (try to) orient the patches toward the tailstock in hopes of simply drilling through them to leave solid plastic around the rim.

Ramming the laser in place makes it look like it grew there;

HQ Sixteen – Stylus Laser – laser test fit

The alert reader will note the lens projects a line, due to my not ordering any dot modules back when I got a bunch of these things. After all, who wants a plain dot when you can light up a line or even a crosshair?

Next, wire it up and stick it on the machine …
2025-02-28
Razor Knife Blade Collet Repair

In the process of fixing something else, I discovered my favorite desktop razor knife had a loose blade. There being nothing like a new problem to take one’s mind off all one’s previous problems, I obviously had to fix it before proceeding:

Razor Knife – broken collet thread

Come to find out the plastic screw tightening the blade collet had snapped. The remaining stub stuck out from the red ribbed nut just far enough to prevent sliding the nut out of the black plastic body, but jamming a small screwdriver through the body got enough traction to unscrew the stub. It’s threaded 8-32, despite being old enough to be Made in Taiwan.

The red plastic feels like HDPE or a similar un-glue-able material, so it was going to need a mechanical splice. A tiny 2-56 setscrew falls in the class of things my buddy Eks describes as “If your design needs those, you’re doing it wrong”, but sometimes you gotta do what you gotta do.

For the record, a 2-56 setscrew requires a 35 mil hex wrench. My tiny ziplock bag with tiny hex wrenches has one:

Razor Knife – 2-56 setscrew

The little wrench in the background measures 28 mils for 0-80 setscrews, of which I have none and don’t expect to get any.

Anyhow, facing, drilling, and tapping the stub proceeded handily:

Razor Knife – setscrew in thread stub

You’d think I hadn’t faced off the end, but you’d be wrong. As far as I can tell, the end of the screw would be happy to break for as long as I’d be willing to try cutting it. Perhaps this indicates why it broke and suggests this repair will be temporary, at best.

Doing the same to the collet required a clamp to fit its slightly oblong body:

Razor Knife – laser-cut collet clamps

Those of long memory may recall the hooks.

Which then worked exactly as you’d expect:

Razor Knife – collet in lathe chuck

That’s aggressive stick-out for a little plastic rod, but sissy cuts saved the day; it faced / drilled / tapped easily enough:

Razor Knife – collet repair parts

Despite the non-glue-able plastic, I tucked some JB PlasticBonder into the recesses, screwed everything together, and coerced the 8-32 threads into alignment inside the plastic nut:

Razor Knife – collet thread alignment

Reassemble in reverse order after the adhesive set up:

Razor Knife – repaired

Done!

Now, what was I doing?

2024-09-11