The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Tag: Repairs

If it used to work, it can work again

Antique Desk Chair: Leg Rebuild

With the seat glued and the old caster sockets yanked, I carved a piece of plywood to fit the gap in one leg:

Wood desk chair – leg filler – bottom

After whittling the wood to kinda-sorta go in there, I pressed it against snippets of carbon paper (remember carbon paper?) to mark the contact points and carve them off:

Wood desk chair – leg filler – carbon paper fitting

This occupied most of a SquidWrench remote meeting, but eventually sank it flush with the leg:

Wood desk chair – leg filler – side

Now, that’s not the prettiest job you’ve ever seen, but it gets worse:

Wood desk chair – leg epoxy shaping

This time around, I tinted the epoxy with brown and black dye, which knocked the color back to something tolerable and increased the curing time well beyond the usual couple of hours. Fortunately, I wasn’t in a hurry and it was pretty much done by the next afternoon.

Whereupon I mixed up another bodacious batch of epoxy:

Wood desk chair – caster pin prep

The Kapton tape wrap kept (most of) the epoxy out of the end of the sockets. I buttered up the sockets just below their serrated heads and tapped them into the legs:

Wood desk chair – caster pin installed

Yeah, I wiped that down a little better before another overnight cure left the four pins firmly secured in their legs; the pins still rotate (albeit stiffly) in the sockets, although the casters really swivel on their pins.

A cast iron fitting of the kind they just don’t make any more holds the legs in place:

Wood desk chair – bottom plate

My screw collection lacks chonky wood screws, but I doubt anybody will ever notice that shiny crosspoint screw.

In any event, the plate holds the legs in tapered slots along the cast iron base that also guides the height adjusting leadscrew under the seat:

Wood desk chair – leg wedge shims

The wood dovetails in the legs were a bit worn / shrunken, so I shimmed them with two strips of 3.5 mil = 0.09 mm stainless steel tape on each side and tapped the legs into place with a plastic mallet. The steel is completely invisible from outside and the legs are magically solid, just like they should be.

As expected, the new casters clash horribly with the chair’s classic style:

Wood desk chair – repaired

Somewhat to my surprise, it’s now undergoing a field test at Mary’s desk, where it replaces a chair she never liked. The seat adjusts down enough to let her feet reach the floor (which most modern chairs do not) and the edge doesn’t press on the back of her legs. We fiddled with the backrest height / angle / tension and it feels surprisingly good.

You gotta admire something with that kind of durability and repairability.

A good refinishing job would definitely improve its appearance, but that’s well beyond my abilities.

2024-06-25
Samsung Dishwasher Screen Filter Fix

The Screen Filter (DD81-02011A) in our Samsung dishwasher (DW80K7050US) turned out to have a mold defect from the factory that’s been sitting there since the previous owners had it installed back in 2018:

Samsung dishwasher screen filter – gap

The mesh apparently didn’t quite make it into the molded plastic, so that little gap has been letting debris in the wash water circulate through the spray bars and clog the orifices.

While replacements are readily available, they seem rather pricey for what they are and this seemed like an easy repair:

Samsung dishwasher screen filter – glued

That’s a bead of EVA hot melt glue that will probably withstand the 163 °F = 73 °C “sanitize” cycle we haven’t had any occasion to use and seems no more toxic than anything else around here.

Protip: if your dishwasher has a filter, it’s likely clogged with a nasty accumulation of gunk, too …

2024-06-24
Antique Desk Chair Woodwork

A wood desk chair that I’ve known since I was a pup finally got some much-needed attention, although not a restoration. By and large, I’m finally sorting out that corner of the basement and needed to put the chair’s parts back together so I can work on something else.

The wood seat consists of several slabs glued along keyed joints, one of which had fractured into a rough mess. Amazingly, the two sides fit perfectly together, albeit with the bottom no longer a planar surface, and glued up just like they should:

Wood desk chair – seat clamping

The chair isn’t up to contemporary office standards, but it has a seat elevation screw, a backrest with adjustable angle & elevation, and even a backrest tension setting:

Wood desk chair – ironwork

It was the cutting edge of desk chair technology:

Wood desk chair – patented

I vaguely recall it rolled on long-vanished steel-wheeled casters. Somewhat less long ago, one of the legs broke enough to lose its caster socket (about which, more later), so I set about yanking the three remaining sockets:

Wood desk chair – caster socket removal

During that struggle, another leg revealed a neat woodwork joint:

Wood desk chair – leg joint

It’s easy to remove a caster socket when you can bash it from the top!

Gluing that piece back in place required Too Many Clamps™ aligning it with the leg:

Wood desk chair – leg clamping

But the end result looks pretty good:

Wood desk chair – leg glued

They did a nice job of matching the wood grain; I hadn’t noticed that joint while attacking the socket.

Pending restoring the broken leg’s socket, the soon-to-arrive new casters will clash horribly with the chair’s woodwork. At least it’ll roll again and its new plastic wheels won’t scar the floors.

2024-06-19
Folding Wood Chair Arm Repair

One of the folding wood chairs that Came With The House™ had a loose arm that turned out to be due to a missing chunk of wood:

Wood chair arm – as found

The obvious lay of the grain shows why it failed like that, surely hastened by the crack below the screw.

So I cut a snippet of brass tubing that, mirabile dictu, fit both the hole and the M6 screw, mixed up some wood epoxy and buttered it up:

Wood chair arm – brass tube epoxy fill

The crack extended entirely through the arm and was more extensive that seemed reasonable to expect the epoxy to handle on its own:

Wood chair arm – splits

So I ~~slobbered~~ ~~soaked~~ saturated the cracks with wood hardener and clamped them shut:

Wood chair arm – clamping

The hardener is intended to solidify rotted wood, but it makes a reasonable adhesive and, being much more liquid than ordinary wood glues, seemed like it would penetrate further into the cracks than anything else on hand. We shall see how this works out.

Rummaging in the Drawer o’ M6 Screws produced a better match to the brass tube than the original flat head screw:

Wood chair arm – repaired

It screws into a fancy tee nut in the upright chair rail, where a dot of thread locker should hold it forevermore.

I hit the exposed end with some sandpaper to smooth off the last of those smears and, after a few years, it’ll probably look like it grew there.

2024-06-07
Laser Cutter: Fourth Corner Adjustment

The pieces of a larger scrap bin ventured into the right-front quarter of the laser platform and didn’t cut well at all:

Fourth Corner beam misalignment – 2024-05-31

A closer look at the bottom right corner of that image shows the problem in more detail:

Fourth Corner beam misalignment – detail – 2024-05-31

The intended cuts are the dark lines, each with a poorly defined scorch 2 mm on its left. Knowing that the nozzle is about 4 mm, this suggests the beam is off-center enough to juuuust kiss the nozzle and splash the outer part of the beam away.

Having recently spot-checked the alignment and not seen any odd behavior on another platform-spanning project, this was puzzling. Given that the laser recently survived a move from one Basement Shop to another, with plenty of jostling while standing on end, I suppose I should have been more careful.

The biggest clue was seeing the shadow lines only near the front-right corner and noting they got worse farther into the corner. This seemed like the “fourth-corner” alignment problem described by St. Sadler some years ago and covered in a more succinct recent video.

AFAICT, the problem boils down to the difficulty of precisely aligning the beam at the longest distance it travels in the front-right corner. Careful adjustment of Mirror 1, after getting everything else lined up properly, seems to be solution.

The initial alignment at the first two mirrors looks OK, using targets taped parallel to the mirror plane:

Beam Alignment – Initial M1 M2 – 2024-05-31

The beam is slightly off-center at Mirror 1 and only a millimeter high on Mirror 2 at either end of the gantry travel along the Y axis.

The beam position at the laser head entry upstream of Mirror 3 shows the problem:

Beam Alignment – Initial M3 entry – 2024-05-31

The targets are left- and right-rear, left- and right-front, with varying pulse lengths obviously underpowering the last and most distant shot.

Looks like a classic fourth-corner problem!

Tweaking Mirror 1 by about 1/8 turn of the adjusting screw to angle the beam vertically upward eventually put the beam dead-center at Mirror 3:

Beam Alignment – M3 adjustments – 2024-05-31

The bottom two targets are double pulses at the left- & right-rear and ‑front, so the beam is now well-centered.

A quick cross-check shows the beam remains centered on Mirror 2 at the front- and rear-end of the gantry travel, Mirror 3 is still OK, and the beam comes out of the center of the nozzle aperture:

Beam Alignment – M2 M3 exit final – 2024-05-31

Subsequent cutting proceeded perfectly all over the platform, so I think the alignment is now as good as it gets or, perhaps, as good as it needs to be.

Whew!

2024-06-05
Balans Chair Re-footing
I’ve been using what’s now called a Multi balans chair since shortly after it came out in the 80s, during which time the plastic feet have worn flat:

Balans chair foot – foot wear

By now, the wood bases ride on the floor, which is a Bad Thing I should have fixed long ago:

Balans chair foot – wood wear

The newer Multi chairs have rolling endcaps, but AFAICT that’s not a retrofittable thing.

The feet have no obvious way to get them out, but after I saw how thin the plastic had become on one foot, some experimental carving solved the problem:

Balans chair foot – OEM foot removal

A large bolt threaded into the crude hole provided enough griptivity to yank the feet out:

Balans chair foot – removed feet

With measurements in hand, I picked up a quartet of furniture leveling feet with M10 stems and tee nuts that exactly fit into the recesses:

Balans chair foot – tee nut fit

I generally buy from sellers who include measurements in their descriptions, although I no longer believe any unit-measurement prices. Most of the time the sizes come out close enough to reality for my simple needs.

The stems were, of course, too long, but that’s easy to fix:

Balans chair foot – cutting stem

The saw does yank the stem down at the last moment, but cutting slow & steady thins the steel and reduces the drama to manageable proportions. Fitting a scrap of wood exactly under the screw would be a much better technique; be it so moved.

With the chair set to the mid-angle position I normally use, the feet meet the floor almost perfectly:

Balans chair foot – straight foot contact

At the steepest angle, things get skewed:

Balans chair foot – angled foot contact

Applying my nearly perfect hindsight, I got a set of swiveling feet and found an appropriate scrap of wood:

Balans chair foot – swivel foot cutting

Zero drama!

Which looks exactly like it should with the chair at the steepest angle:

Balans chair foot – swivel foot contact

The chair now sports two pairs of feet:
- Straight feet on the rear
- Swivel feet on the front
Now, to see how they survive on a chair, rather than motionless furniture.

If you have any idea why the WordPress AI image generator would come up with this, let me know:

Balans chair foot – WP AI image

That’s not hallucination, it’s just plain irrelevant.

For the record, we also have a couple of equally ancient Variable balans chairs.
2024-06-03
Improvised Table Leg Latch

While setting up the small table I conjured from scrap, I discovered one of the folding legs no longer had a latch to keep it from folding. Whether it never had one or the latch got lost along the way, there’s no time like the present:

Table leg latch – installed

The bolt I put there in place of the joint rivet precludes a smaller latch along the lines of the simple steel loop on the other leg, so I figured I may as well go large and, with that much surface area, plywood will work just as well as steel for my simple needs.

It’s a topless, bottomless box from the infinite supply at boxes.py, here seen with its halves being glued at right angles on an aluminum bracket:

Table leg latch – gluing

When those set, I glued & clamped them together in situ, then wrapped the whole mess with what’s basically high-strength friction tape to encourage it to not come too far apart under the inevitable stress when the leg tries to fold with a pile of stuff on the table.

We’ll see how long this survives; if past experience is any guide, it’ll be a while.

The WordPress AI image generator has a shaky grasp of both human anatomy and the blog topic:

Woodwork design by Escher. What is that interesting tool? So many arms, all with nightmare fuel anatomy!

2024-05-31