Posts Tagged Mini-lathe
Bird Feeder Unbending
Posted by Ed in Home Ec, Machine Shop, Science on 2018-11-13
At some point in its history, the left rail holding the wood perch on our industrial-strength “squirrel proof” seed feeder took a hit, most likely from being dropped:
Squirrel on bird feeder
I finally got a Round Tuit and un-bent the poor thing:
Bird feeder – rail un-bending
Because the bend happened at the base of the vertical strut holding the shutter, I clamped a Genuine Vise-Grip sheet metal pliers along the straight section. The Craftsman knock-off Vise-Grip then applied torque at the bend, rather than just making things worse, and some two-axis tweakage lined up the rail pretty well.
With the bend taken care of, I clamped the rail in the bench vise with some scrap wood around the strut:
Bird feeder – warped rail
A percussive adjustment jam session flattened the top flange, leaving both sections as flat as they’re gonna get.
While I was at it, I turned a pair of stepped aluminum washers for the new wood rod:
Bird feeder – parting off washer
Which looked about like you’d expect, including a little chatter from the cut off tool:
Bird feeder – perch hardware
Yeah, I drilled the wood rod on the lathe, too; I loves me some simple lathe action.
Reassemble in reverse order and it’s all good:
Bird feeder – perch installed
We’re supposed to bleach the feeder every week to kill off the bacteria causing House Finch Eye Disease and, while I can’t promise a weekly schedule, we’ll (try to) reduce the amount of crud on the feeder this year.
If you’ve got a feeder, sign up for Project Feederwatch and do some citizen science!
Kenmore Progressive Vacuum Tool Adapters: Third Failure
Posted by Ed in Home Ec, Machine Shop, Software on 2018-11-08
The adapter for an old Electrolux crevice tool (not the dust brush) snapped at the usual stress concentration after about three years:
Crevice tool adapter – broken vs PVC pipe
The lower adapter is the new version, made from a length of 1 inch PVC pipe (that’s the ID, kinda-sorta) epoxied into a revised Kenmore adapter fitting.
The original OpenSCAD model provided the taper dimensions:
Electrolux Crevice Tool Adapter – PVC taper doodles
The taper isn’t quite as critical as it seems, because the crevice tool is an ancient molded plastic part, but a smidge over half a degree seemed like a good target.
Start by boring out the pipe ID until it’s Big Enough (or, equally, the walls aren’t Scary Thin) at 28 mm:
Crevice tool adapter – boring PVC
Alas, the mini-lathe’s craptastic compound has 2° graduations:
Minilathe compound angle scale
So I set the angle using a somewhat less craptastic protractor and angle gauge:
Crevice tool adapter – compound angle
The little wedge of daylight near the gauge pivot is the difference between the normal perpendicular-to-the-spindle axis setting and half-a-degree-ish.
Turning PVC produces remarkably tenacious swarf:
Crevice tool adapter – PVC swarf
The gash along the top comes from a utility knife; just pulling the swarf off didn’t work well at all.
The column of figures down the right side of the doodles shows successive approximations to the target angle, mostly achieved by percussive adjustment, eventually converging to about the right taper with the proper dimensions.
Cutting off the finished product with the (newly angled) cutoff bit:
Crevice tool adapter – cutoff
And then It Just Worked™.
The OpenSCAD source code for all the adapters as a GitHub Gist:
Modifying a 2.5 mm Collet Pen Holder for a 3 mm Diamond Engraver
Posted by Ed in Machine Shop on 2018-11-06
Of course, the diamond engraving points have a 3 mm shaft that doesn’t fit in the 2.5 mm Collet Pen Holder, but making a hole bigger isn’t much of a problem …
Start by drilling out the collet closer nut:
Collet Holder – closer nut drilling
The hole didn’t start out on center and I didn’t improve it in the least. A touch of the lathe bit and a little file work eased off the razor edge around the snout.
The knurled ridges at the top are larger than the threaded body, which requires a shim around the threads to fit them into the lathe chuck. Start by cutting a slightly larger ID brass tube to the length of the threaded section:
Collet Holder – brass shim cutoff
I finally got a Round Tuit and ground opposing angles on the cutoff tool ends, so I can choose which side of the cut goes through first. In this case, the left side cuts cleanly and the scrap end carries the thinned slot into the chip tray.
Grab the tube in a pair of machinist vises and hacksaw a slot:
Collet Holder – brass shim slitting
Apply a nibbler to embiggen the slot enough to leave an opening when it’s squashed around the threads:
Collet Holder – brass shim around threads
Put a nut on the collet threads in an attempt to keep them neatly lined up while drilling:
Collet Holder – collet drilling
Drill the hole to a bit over 3 mm in small steps, because it’s not the most stable setup you’ve ever used. Eventually, the diamond point just slips right in:
Collet Holder – 3 mm scribe test fit
Reassemble in reverse order and It Just Works:
Collet Holder – finished
Now, to scratch up some acrylic!
Cheese Slicer Rebuild
Posted by Ed in Home Ec, Machine Shop on 2018-11-05
The cheese slicer frame looked much better after sandblasting with 220 aluminum oxide grit:
Cheese slicer – sandblasted
The flower bed outside the Basement Laboratory door seems a bit dusty, though.
Slathering it with JB Weld steel-filled epoxy went reasonably well:
Cheese slicer – JB Weld curing
JB Weld is much much more viscous than the clear XTC-3D I used last year and the final coating, while smoother than what you see here, has too many sags and dents to say “good job”. I didn’t bother coating the upper tips, because the epoxy will wear off from my morning KP.
The aluminum roller turned on those bare stainless steel screws in the tray, with the threads chewing into the roller bore. While the epoxy was curing, I drilled out the roller to remove most of the ridges:
Cheese slicer – drilling roller
Cut a pair of stainless screws slightly longer than the old screws, then turn the threads off to make a shaft:
Cheese slicer – screw reshaping
The lathe spindle runs in reverse, so the cutting force tends to tighten the screw in the nuts. The big old South Bend lathe had a screw-on chuck and didn’t really like turning backwards.
The new screws won’t win any beauty prizes, but they get the job done:
Cheese slicer – screw shafts
Turn a Delrin rod to a press fit in the drilled-out roller:
Cheese slicer – turning Delrin bearing
Part it off, repeat, ram them into the roller, then drill to a loose fit around the smooth-ish screw shafts:
Cheese slicer – drilling Delrin bearing
Reassemble in reverse order:
Cheese slicer – rebuilt
Looks downright industrial, it does.
Stipulated: this makes no economic sense, apart the simple fact we appreciate utensils that just work.
Doorknob Repair
Posted by Ed in Home Ec, Machine Shop on 2018-10-22
The outer doorknob on the kitchen pantry became very loose and sloppy, with the screw holding the inner knob on the shaft remaining snug. Obviously, something else was wrong inside the door.
A spring clip should retain the outer knob in the escutcheon:
Doorknob – worn retaining flange – detail
The flange holding the clip has worn away, letting the clip fall loose. A side view shows the problem:
Doorknob shaft – worn retaining flange
Yes, the knob’s chrome plating is in sorry shape after six decades of wear. I’d rather keep using a solid knob, instead of force-fitting some contemporary half-assed / cost-reduced junk into the door.
Reference: beausage. I say it “beau-sage”, the beauty that comes from usage.
The shaft consists of three triangular rods, with the setscrew on the inner knob pressing against the smaller rod to lock all three of them in place and eliminate all rattle & play:
Doorknob shaft – detail
A tapered pin (!) locks the three shaft rods into the outer knob:
Doorknob shaft – tapered pin
Some doodling, most of which turned out to be irrelevant, captured the essential dimensions and suggested how to replace the flange:
Doorknob – dimension doodles
The stock is 11/16 inch O-1 oil-hardening rod, forever to remain unhardened:
Doorknob – retainer ring boring
I drilled a few holes to get up to 1/2 inch, the largest drill bit I have and just barely clearing the the boring bar.
With the hole bored out to fit the end of the knob, cut it off:
Doorknob – retainer ring cutoff
Trial-fit the ring on the knob with the spring clip:
Doorknob – retainer trial fit
Reinstall the shaft, tap in the retaining pin, then epoxy the ring in place with the knob supported from below to eliminate having to fiddle with the spring clip:
Doorknob – retainer ring epoxy
Add a few dots of oil here & there, reinstall the parts in reverse order, and the knob works perfectly again. Still looks heavily used, of course, but that’s OK.
They definitely don’t make ’em like that any more …
Presta Valve to Schraeder Hole Adapter
Posted by Ed in Machine Shop, Recumbent Bicycling on 2018-08-02
The front rim on my Tour Easy developed a distinct bulge, of the sort usually caused by ramming something, but I’m not Danny McAskell and the bulge got worse over the course of a few weeks, suggesting the rim was deforming under tire pressure. Having ridden it upwards of 35 k miles with plenty of trailer towing and too much crushed-stone trail riding, the brake tracks were badly worn and it’s time for a new rim.
An Amazon seller had an identical (!) rim, except for the minor difference of having a hole sized for a Schraeder valve stem, rather than the Presta valves on the original rims. One can buy adapters / grommets, but what’s the fun in that?
The brake track walls are 1.5 mm thick on the new rim and a scant 1.0 mm on the old rim, so, yeah, it’s worn.
A few measurements to get started (and for future reference):
Presta to Schraeder Adapter – dimension doodle
If you don’t have an A drill, a 15/64 inch drill is only half a mil larger and, sheesh, anything close will be fine.
Introduce a suitable brass rod to Mr Lathe:
Presta-Schraeder Adapter – parting off
Break all the edges and drop it in place:
Presta-Schraeder Adapter – installed
One could argue for swaging the adapter to fit flush against the curved rim, but commercial adapters don’t bother with such refinements and neither shall I.
The 7.0 mm length got shortened to fit flush with the center of the rim:
Presta-Schraeder Adapter – valve stem installed
It’s brass, because the rim is heaviest on the far side where the steel pins splicing the ends live, and, with the tube & tire installed, the rim came out almost perfectly balanced. Which makes essentially no difference whatsoever, of course.
The shiny new rim sports shiny new reflector tape (from the same stockpile, of course).
That was easy …
MPCNC: Ground Shaft Pen Holder
Posted by Ed in Machine Shop on 2018-04-18
Drilling a pair of holes into a length of ground steel shaft turned it into a holder for a Sakura Micron pen:
DW660 Pen Holder – printed plastic vs ground steel
The aluminum ring epoxied to the top keeps it from falling completely through the linear bearing.
The hole sizes are the nearest inch drills matching the pen’s hard metric sizes:
Ground 12 mm rod – Sakura pen drill diameters
While I was at the lathe, I turned another layer of epoxy on the printed holder down to a consistent 11.95+ OD. It fits the bearing nearly as well as the steel shaft, although it’s not quite as smooth.
The steel version weighs about 20 g with the pen, so it applies about the same downforce on the pen nib as the HP 7475A plotter. The force varies from about 19 g as the Z axis moves upward to 23 g as it move downward, so the stiction amounts to less than 10% of the weight:
DW660 Pen Holder – ground shaft
However, the more I ponder this setup, the less I like it.
When the Z-axis moves downward and the nib hits the paper, it must decelerate the weight of the pen + holder + ballast within a fraction of a millimeter, without crushing the nib. If the pen moves downward at 3000 mm/min = 50 mm/s, stopping in 0.3 mm requires an acceleration of 4.2 m/s² and a 20 g = 2/3 oz mass will apply 0.08 N = 0.3 oz to the nib. Seems survivable, but smashing the tip a few hundred times while drawing the legends can’t possibly be good for it.
Also, the tool length probe switch trips at 60 (-ish) g, which means the pen can’t activate the switch. Adding a manual latch seems absurd, but you can get used to anything if you do it enough.
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