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: Improvements

Making the world a better place, one piece at a time

MPCNC Drag Knife Holder: Lock Screw

While calibrating the MPCNC’s probe camera offset for the drag knife holder, this happened:

Drag Knife – vertical escape

Well, at least it’s centered on the target:

Drag Knife – vertical escape – detail

This happened a few times before, because my fingers don’t fit neatly inside the drag knife holder to tighten the lock ring:

Drag Knife – LM12UU ground shaft – assembled

[Update: The lock ring keeps the holder at a fixed position inside the 12 mm shaft and doesn’t affect the blade directly. When the ring works loose, the threaded holder can rotate to expose more blade and, in this case, stab deeper into the target. ]

So I turned & knurled an aluminum ring, then tapped a 3×0.5 mm hole for a lock screw plucked from the Drawer o’ Random M3 Screws:

Drag Knife – lock screw – side

A view looking along the screw shows a bit more detail around the spring:

Drag Knife – lock screw – front

The general idea is to set the blade extension, then tighten the lock screw to hold it in place, without relying on the original brass lock ring, shown here while cutting a boss for the spring:

Drag Knife – turning spring recess

The lock screw’s knurled handle just barely kisses the NPCNC’s black tool holder ring, so my guesstimated measurements were a bit off. Clamping the knife holder one itsy higher in the tool holder solved the problem.

I cranked on 300 g of spring preload and, squashed like that, the spring’s rate is now 75 g/mm. Cutting at Z=-1 mm should suffice for laminated paper slide rule decks.

The original sizing doodle:

Drag Knife Holder – lock screw ring doodle

The short 18 mm section clears the inside of the LM12UU bearing, although it could be a millimeter shorter. The 19 mm section comes from the 3/4 inch aluminum rod I used, skim-cut to clean it up.

If I ever remake this thing, it needs a major re-think to get all the dimensions flying in formation again.

2020-01-21
Photo Lamp Mount: Moah Plastic!

One of the cold shoe mounts I made for the photo lamps cracked:

$Photo Lamp Mount - fractured$
Photo Lamp Mount – fractured

It’s done in PETG with my more-or-less standard two perimeter threads and 15% 3D honeycomb infill, which is Good Enough™ for most of my parts. In this case, there’s obviously not nearly enough plastic in there!

Redoing it with three perimeters and 50% infill should improve the situation, even though it looks identical on the outside:

Photo Lamp Mount – reinstalled

I didn’t replace the other mount. If it breaks, it’ll get the same 50% infill as this one. If this one breaks, I’ll try 75%.

An easy fix!

2020-01-19
Eyelet Punch Reshaping

The hollow punch included with the 5.5 mm eyelet / grommet set had a rather blunt cutting edge:

Eyelet punch – OEM taper

The rainbow colors along the tapered cut suggested at least token hardening of the edge, so I mounted it in the lathe chuck, deployed a rag over the bed ways to collect the dust, and spun it at a few hundred RPM while freehanding the edge with a Dremel heavy-duty slitting wheel resting on the compound:

Eyelet punch – reshaped

It’s not what you’d call “hollow ground”, but at least the edge doesn’t force the outside of the cut surface quite so far outward.

The Tek Circuit Computer decks get their pivot holes cut with a drag knife on the MPCNC, but I won’t be too embarrassed the next time I deploy this thing.

2020-01-18
Schwab / Symantec VIP Access vs. Yubikey
A Yubikey 5 NFC turns out to be perfectly compatible with any website using Symantec’s (no longer available) hardware key and VIP Access (definitely a misnomer) app to generate TOTP access codes, because the sites use bog-standard TOTP. The only difficulty comes from Symantec’s proprietary protocol creating the token linking an ID with a secret value to generate the TOTP codes, which is how they monetize an open standard.

Fortunately, Cyrozap reverse-engineered the Symantec protocol, dlenski mechanized it with a Python script, and it works perfectly:
```
python3 -m venv symkey-env
source symkey-env/bin/activate
pip3 install https://github.com/dlenski/python-vipaccess/archive/HEAD.zip
vipaccess provision -t SYMC
deactivate
```
That spits out a file containing the ID and secret, from which you create a QR code for the Yubikey Authenticator app:
```
qrencode -t UTF8 'otpauth://totp/VIP%20Access:SYMCidnumbers?secret=longsecretgibberish&issuer=Symantec&algorithm=SHA1&digits=6'
```
Fire up the app, wave the Yubikey behind the phone, scan the QR code, wave the Yubikey again to store it, sign in to the Schwab site, turn on 2FA, enter the ID & current TOTP value from the Yubikey Authenticator, and It Just Works™.

Of course, you can kiss Schwab’s tech support goodbye, because you’re on your own. If you ever lose the Yubikey, make sure you know the answers to your allegedly secret questions.

Equally of course, you’re downloading and running random shit from the Intertubes, but …

Now, if only all my financial institutions would get with the program.
2020-01-16
Needle Case Repair

A needle case emerged from the bottom of a drawer in need of repair:

Needle Case – unglued

The original joint used solvent glue and I suppose I could refresh it with acetone, but two blobs of hot melt glue seemed easier and, IMO, more durable.

In any event, it’s once more ready for use:

Needle Case – repaired

Hooray for another zero-dollar repair, although you can see why nobody else does them these days.

2020-01-12
Alkaline Battery Packaging

Apparently, we’ve burned enough cargo aircraft and killed enough people to require careful attention to detail in battery packages:

Amazon alkaline AAA packaging

These “Ships from and sold by Amazon” alkaline AA cells arrived by UPS. They now fall under reasonable requirements to prevent shorting and damage, although the cardboard box wasn’t sturdy enough to prevent them from breaking free laterally.

One might quibble about the “Health & Personal Care Item” description, but, yeah, better battery packaging seems like a good idea.

2020-01-11
Homage Tektronix Circuit Computer: Colored Scales

Although the original Tektronix Circuit Computer had relentlessly monochrome scales, a dash of color added a festive holiday look:

Tek CC – Pilot V5 – color test overview

Well, OK, that’s excessive.

The intent was to see how the pens behaved, with an eye toward accenting general-purpose circular slide rule scales with a few colored characters.

The green pen shows how I built the arrows by drawing a line through vertical arrow characters:

Tek CC – Pilot V5 – plain paper – letters

I like blue ink entirely too much, having used a blue pen as my daily writer for most of my adult life:

Tek CC – Pilot V5 – plain paper – red blue

Red ink for “backwards” scales and suchlike would work well, even if it’s too vivid for the tick marks:

Tek CC – Pilot V5 – plain paper – red green

Those are all on unlaminated plain paper, with plenty of room for improvement.

Seeing as how I’d be doing all the “tool changes” manually, optimizing the plotting sequence would be mandatory: one pen change per color per deck!

2020-01-09