The Smell of Molten Projects in the Morning
Ed Nisley's Blog: shop notes, electronics, firmware, machinery, 3D printing, and curiosities
Tweaking an LMS 5200 Mini-Lathe
Unsurprisingly, the mini-lathe lacks enough stiffness to apply enough force to hold a disk in place while turning its rim:
The old South Bend lathe had mojo, but those days are gone.
So drill and tap that fixture for an M3 screw, then stick some coarse sandpaper to it:
Snug the screw (a Torx T9 from the Small Drawer o’ Random M3 Screws) down on a rough-cut disk:
Sissy cuts remain the order of the day, but the screw applies plenty of clamping force and doesn’t require the hulking live center.
Finishing the PVC tubes reinforcing the vacuum cleaner adapters required fixtures on each end:
Because the tubes get epoxied into the adapters, there’s no particular need for a smooth surface finish and, in fact, some surface roughness makes for a good epoxy bond. The interior of a 3D printed adapter is nothing if not rough; the epoxy in between will be perfectly happy.
Turning the tubes started by just grabbing the conduit in the chuck and peeling the end that stuck out down to the finished diameter, because the conduit was thick-walled enough to let that work.
The remaining wall was so thin that the chuck would crunch it into a three-lobed shape, so the white ring in the chuck is a scrap of PVC pipe turned to fit the tube ID and provide enough reinforcement to keep the tube round.
The conduit ID isn’t a controlled dimension and was, in point of fact, not particularly round. It was, however, smooth, which counts for more than anything inside a tube carrying airborne fuzzy debris; polishing the interior of a lathe-bored pipe simply wasn’t going to happen.
The fixture on the other end started as a scrap of polycarbonate bandsawed into a disk with a hole center-drilled in the middle:
Stick it onto a disk turning fixture and sissy-cut the OD down a little smaller than the eventual tube OD:
Turn the end down to fit the tube ID, flip it around to center-drill the other side, stick it into the tube, and finally finish the job:
The nice layering effect along the tube probably comes from molding the conduit from recycled PVC with no particular concern for color matching.
A family portrait of the fixtures with a finished adapter:
A fine chunk of Quality Shop Time: solid modeling, 3D printing, mini-lathe turning, and even some coordinate drilling on the Sherline.
Being the domain expert for adapters between a new vacuum cleaner and old tools, this made sense (even though it’s not our vacuum):
The notch snaps into a Dirt Devil Power Stick vacuum cleaner and the tapered end fits a variety of old tools for other vacuum cleaners:
Having some experience breaking thin-walled adapters, these have reinforcement from a PVC tube:
A smear of epoxy around the interior holds the tube in place:
Building the critical dimensions with a 3D printed part simplified the project, because I could (and did!) tweak the OpenSCAD code to match the tapers to the tools. Turning four of those tubes from a chunk of PVC conduit, however, makes a story for another day.
The OpenSCAD source code as a GitHub Gist:
| // Dirt Devil nozzle adapter | |
| // Ed Nisley KE4ZNU 2021-10 | |
| // Tool taper shift | |
| Finesse = -0.1; // [-0.5:0.1:0.5] | |
| // PVC pipe liner | |
| PipeOD = 28.5; | |
| /* [Hidden] */ | |
| //- Extrusion parameters | |
| ThreadThick = 0.25; | |
| ThreadWidth = 0.40; | |
| HoleWindage = 0.2; | |
| function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit); | |
| Protrusion = 0.1; // make holes end cleanly | |
| //---------------------- | |
| // Dimensions | |
| TAPER_MIN = 0; | |
| TAPER_MAX = 1; | |
| TAPER_LENGTH = 2; | |
| Socket = [36.0,37.0,40.0]; | |
| LockringDia = 33.5; | |
| LockringWidth = 4.5; | |
| LockringOffset = 2.5; | |
| Tool = [Finesse,Finesse,0] + [30.0,31.1,30.0]; | |
| AdapterOAL = Socket[TAPER_LENGTH] + Tool[TAPER_LENGTH]; | |
| NumSides = 36; | |
| $fn = NumSides; | |
| //---------------------- | |
| // Useful routines | |
| module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes | |
| Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2); | |
| FixDia = Dia / cos(180/Sides); | |
| cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides); | |
| } | |
| //------------------- | |
| // Define it! | |
| module Adapter() { | |
| difference() { | |
| union() { | |
| difference() { | |
| cylinder(d1=Socket[TAPER_MIN],d2=Socket[TAPER_MAX],h=Socket[TAPER_LENGTH]); | |
| translate([0,0,LockringOffset]) | |
| cylinder(d=2*Socket[TAPER_MAX],h=LockringWidth); | |
| } | |
| cylinder(d=LockringDia,h=Socket[TAPER_LENGTH]); | |
| translate([0,0,LockringOffset + 0.75*LockringWidth]) | |
| cylinder(d1=LockringDia,d2=Socket[TAPER_MIN],h=0.25*LockringWidth); | |
| translate([0,0,Socket[TAPER_LENGTH]]) | |
| cylinder(d1=Tool[TAPER_MAX],d2=Tool[TAPER_MIN],h=Tool[TAPER_LENGTH]); | |
| } | |
| translate([0,0,-Protrusion]) | |
| PolyCyl(PipeOD,AdapterOAL + 2*Protrusion,NumSides); | |
| } | |
| } | |
| //---------------------- | |
| // Build it! | |
| Adapter(); | |
The taper in the code almost certainly won’t fit whatever tool you have: measure thrice, print twice, and maybe fit once …
There being nothing like a good new problem to take one’s mind off all one’s old problems:
It’s basically the same as the lower blade guide, except coming from a stick of 5/8 inch acetal. A scant 6 mm stem goes into the vertical square rod, with a flat matching the setscrew coming up from the bottom to hold it in proper alignment.
I came within a heartbeat of cutting the slot parallel to the flat.
It worked OK while cutting a chunk of stout aluminum tube: so far, so good!
The impressive chunk of hardware is the OEM blade guide, with the brass tube for coolant flow all over the bearings. It’s mostly intended for use with the diamond blade, so I’ll swap it back in when I finally get around to cutting some slate for base plates.
Because the rear running light will have a higher duty cycle than the front light, I made the (admittedly too small) heatsink slightly longer, with a deeper recess to protect the lens from cargo on the rear rack:
Boring that nice flat bottom is tedious; I must lay in a stock of aluminum tubing to simplify the process.
Drilling the holes went smoothly:
Those two holes fit a pair of pins aligning the circuit plate, with a screw and brass insert holding it to the heatsink. Scuffing a strip across the aluminum might give the urethane adhesive (you can see uncured globs on the pins) a better grip:
The screw / insert /pins are glued into the plate to permanently bond it to the heatsink. The screw occupies only half of the insert, with the longer screw from the end cap pulling the whole affair together.
The two holes on the left pass both LED leads to one side of the circuit plate, where they connect to the current regulator and its sense resistor.
The same lathe fixture and double-sided duct tape trick I used for the amber running light’s end cap should have worked for this one, but only after I re-learned the lesson about taking sissy cuts:
Yet another snippet of tape and sissy cuts produced a better result:
Protip: when you affix an aluminum disk bandsawed from a scrap of nonstick griddle to a lathe fixture, the adhesive will grip the disk in only one orientation.
The Micro-Mark bandsaw has a metal blade guide below the table that contributes to the awful noise it makes while running, even when it’s not cutting anything. Having recently touched the Delrin = acetal rod stash, a simple project came to mind.
A doodle with the original metal guide dimensions:
The 10 mm dimension is non-critical, so I started with a 1/2 inch acetal rod and turned the stub end to match.
A doodle suggested how to carve the slot with a 20.5 mil = 0.52 mm slitting saw, with the offset from a Z touchoff at the top:
The V block setup required swapping out the overly long OEM screw for a shorter 5 mm SHCS to clear the Sherline’s motor:
The end result looked pretty good:
And it looks like it pretty much belongs in the saw:
The 6 mm stud goes into a hole in the frame, where a setscrew holds it in place. You must remove the blade to extract / replace the guide, with the correct position having the end of the slot just touching the back of the blade.
The foam ring apparently keeps crud away from the stud on the backside; I doubt it’s mission-critical.
The saw became somewhat quieter; the ball bearing guides above the table now generate most of the racket. At some point I’ll try replacing them with a block, probably made from UHMW, with a simple slit to guide the blade.
Plastic guides may not last as long as the steel ones, but occasional replacements will be worth it if the saw runs quieter.
The Smell of Molten Projects in the Morning 