So the question came up: “Exactly what happens when one of those things gets wet?”
Which obviously requires an experiment:
Laminated Tek CC vs Water – start
That’s the mis-cut top deck revealing why GRBL really needs four digits after the decimal point, but, other than that, it’s perfectly representative of the genre: heavy paper, good ink, nicely laminated in plastic.
Prediction: water should seep into the paper, dissolve the ink, maybe delaminate the plastic, and generally make a mess.
I gimmicked a scanner fixture to align a pair of pages:
Pickett 110-ES Scanning Fixture
Yes, I destroyed the collectible value of my manual by removing two slightly rusted staples.
The black paper taped to the scanner lid prevents the type on the upper surface of the paper from producing dark blurs.
Set up XSane for batch scanning (one selection over each two-page spread), get a pipeline going (disassembly → face up → face down → reassembly), and eventually create 34 images named Scan-??.jpg. They’re in color, although it matters only for the rust stains around the staple holes, with the contrast stretched enough to make them mostly B&W.
Somehow, Pickett printed / cut half the sheets slightly off-kilter, so I rotated them -1° rotation to re-align the text. To simplify plucking the rotated pages out of the image, composite the spread atop a blank white background:
for i in $(seq -w 3 2 33) ; do composite -compose atop Scan-$i.jpg -size 2200x1400 -geometry +100+100 canvas:white -rotate -1 Comp-$i.jpg ; done
Rather than thinking too hard, do exactly the same thing to the other pages without rotation:
for i in $(seq -w 2 2 34) ; do composite -compose atop Scan-$i.jpg -size 2200x1400 -geometry +100+100 canvas:white -rotate 0 Comp-$i.jpg ; done
Each scanned image has two pages, so crop it into two files with names corresponding to the actual page numbers:
for i in $(seq 2 2 34) ; do convert -crop 960x1240+1050+110 Comp-$i.jpg Crop-$(( $i - 1 )).jpg ; done
for i in $(seq 3 2 34) ; do convert -crop 960x1240+130+110 Comp-$i.jpg Crop-$(( $i - 1 )).jpg ; done
for i in $(seq 3 2 33) ; do convert -crop 960x1240+1050+110 Comp-$i.jpg Crop-$(( 66 - $i )).jpg ; done
for i in $(seq 2 2 32) ; do convert -crop 960x1240+110+110 Comp-$i.jpg Crop-$(( 66 - $i )).jpg ; done
Fix the single-digit pages to simplify globbing later on:
rename 's/-/-0/' Crop-[1-9].jpg
A bit of tedious fixup for some truly misaligned sheets produced images with slightly different sizes, so composite all of them onto slightly larger backgrounds to avoid screwing up the PDF conversion:
mkdir Final
for f in Crop* ; do composite -compose atop $f -size 1000x1300 -geometry +10+10 canvas:white -Final/$f ; done
Then jam them into a PDF for convenience:
cd Final
convert Crop-C[12].jpg Crop-[0-6]*.jpg Crop-C[34].jpg "Pickett 110-ES Circular Slide Rule Manual.pdf"
You can print it six-up to a sheet to produce text just about the same size as the original manual. If you omit (blank) cover pages 2, 67, and 68, the whole thing fits neatly on 11 sheets of paper.
Someone with better facilities and more attention to detail can surely produce a better-looking result, but this will be better than nothing.
It’s not a Purple Crayon, but it suffices for my simple needs.
Scribbling a (soft!) lacquer crayon over transparent plastic still scuffs the pristine surface around the engraved line, so I tried scribbling the six-pass cursor before peeling the film, as shown above. Unfortunately, the film shreds left around the line either prevent a clean fill or pull the paint out of the ditch as the film peels back:
Tek CC – Cursor lacquer fill
Peeling the film and scribbling ever-so-gently left a more complete line, but, if you look very closely (perhaps opening the image in a new tab for more dots), you can see the scuffs left by the scribbles on either side of the line:
Tek CC – Cursor 2 4 6 scribes
When seen from the other side against laminated decks, though, the scuffs pretty much vanish:
Tek CC – Classic Tek Logo vectorized – red hairline
Although Inkscape can lay out simple text in many intricate ways, there seems no way to typeset mathematical equations, even the simple ones involved in the Tektronix Circuit Computer.
So I entered the equations in LibreOffice’s math editor, zoomed in on each equation to the maximum 600%, whacked the little-used PrntScr key, cropped out everything except the equation, and saved it as a PNG file:
Tek CC – Bottom Deck Back – FR formula
Import the PNG files into Inkscape, fiddle with the line spacing to get enough room, and jockey everything into position:
Tek CC – Milled PETG cursor – Lacquer-Stik hairline
This time, I had the clear film on top!
Although the picture doesn’t do it justice, the scales are in blue ink, which looks better against the yellow background. I suppose I could do custom colors:
Pilot V5RT cartridge – ink levels
The line width has decreased as the ink level drops: 0.3 mm on yellow card stock and 0.2 mm on glossy white brochure paper. I don’t know if they’re supposed to work like that, but, for this application, narrower lines are definitely better.
A separate instruction manual told you how to use the thing, under the reasonable assumption you’d be intimately familiar with slide rules.
In this day and age, the back should carry how-to-use instructions, so I summarized the manual into half a dozen lists:
Tek CC – instructions – first pass
Which looked fine & dandy & ready to print, thereby exposing various typos / inconsistencies / misalignments:
Tek CC – test print – HP Brochure vs ordinary copy paper
Whereupon I (re)discovered just how much paper matters.
The HP Brochure Glossy inkjet paper on the left produces wonderful results with a 0.5 mm Pilot V5RT ball point pen and has coating on both sides. It’s intended for handouts, brochures, and suchlike; the Pilot pens produce identical results on either side.
The same text, printed on plain old 22 pound “multipurpose” paper on the right, looks much better and makes the HP paper looks like something done with crayon on paper towel.
I could try a font with finer strokes, but … ick.
It’s unclear whether Brochure Matte paper would make any difference, nor whether running coated “inkjet” paper through a laser printer would have an … infelicitous … outcome.
Past experience shows the unsteady ziggurat of Linux printing doesn’t respond well to tweakage: when the default settings don’t work, there’s no easy / predictable way to change any particular setting.
For future reference, print the instruction on what will become the back of the bottom deck, mark the center point, tape it to the CNC 3018 platform, touch off XY = 0 at the center, and draw the front scales: everything lines up perfectly without extra fuss & bother.
Based on manually scratching some acrylic, the GCMC code retraced the hairline four times to help the Sharpie stick to the groove. Maybe fewer passes would be better?
Affix a PETG scrap to the milling fixture for some manual CNC action:
PETG – engrave through film
Just to see what happened, I made the first scratch through the protective film and, because it’s hard to tell which side is up, the scratch went through the white film.
Repeat several times with variations in number of passes & downforce:
The absolute best-looking line is at the top, with the diamond point scribing through the (white) protective plastic film.
Multiple passes average out the waves / glitches / irregularities, at the cost of broadening the hairline.
The bottom hairline suggests a single pass with more downforce produces a broader groove and a finer line of Sharpie ink at the bottom; the top appears more rounded and the bottom more ragged.
Doing one pass with enough pressure to cut through the thinner (?) transparent(-ish) film may produce a better overall result. This will require me to get the orientation right.
The Real Hairline in my K&E Deci-Lon slipstick is a smoothly engraved, neatly half-cylindrical, channel with a smooth thread of red (!) ink / paint / pigment laid along the middle. Obviously, my engraving hand is weak …
The nightmare scenario: engraving a smooth hairline groove, completely backfilling it with paint, sanding (that side of) the cursor smooth to leave the groove’s paint flush with the surface, then polishing the plastic back to full transparency. Even I agree that’s crazy talk, at least for a circular slide rule made with laminated paper decks.
