« Archives in March, 2021

Interesting Reading

Some interesting things I’ve been reading this year:

The Wright Bros by David McCollough is an interesting biography of the inventors of controlled heavier-than-air flight. One fascinating part was a reference to a speech made by Wilbur Wright at the Western Society of Engineers.

Link to my copy of the speech: “Some Aeronautical Experiments”, Wilbur Wright, 1901:


Link to where I obtained it from: Link
Link to the biography: The Wright Brothers, David McCollough

This is one example of what a first rate mind approaching a problem looks like. Wilbur makes it clear that the principal difficulty that he and his brother were tackling at Kitty-Hawk was the problem of controlling the vehicle while in the air. They built up the knowledge to do so with an extensive series of glider experiments. The experiment-heavy, experience heavy and iterative nature of their self-directed program contrasts with other efforts to build flying machines at the time: A large upfront investment made in an expensive machine which promptly crashes.

While the Wright Bros faced some pretty stiff incredulity and cynicism, most of that cynicism came from the world of the press and humanities. There was a fairly serious and supportive community of engineers who were making efforts to tackle the problem of heavier-than-air flight. (The Dayton Daily news refused to acknowledge their accomplishments, even as they were doing laps around Huffman Prarie. It fell to a Kentucky almanac run by a beekeeper to provide their first publicity!)

Book Workbench Python Scripts

Link to the scripts

Book Dumping and Book Binding Scripts

Aaron M. Schinder

18 Mar 2021


These scripts are intended to dump image files from pdfs and bind image files into pdfs. I wrote these primarily to convert Archive.org pdfs from the highly compressed format they use to less compressed but more readable pdfs built from the images.

The various Linux pdf readers have difficulty unpacking archive.org books. It’s a known problem. (It takes a very long time to load pages in whatever format or scheme archive.org uses internally)

The idea here is that hard drive space is cheaper than time, especially the loading time for the pages which may make paging and skimming through a book untenable. Paging through images can be done almost as fast as flipping through a physical book, so it doesn’t impede using them in a similar manner.


These tools were written to work on Linux (I don’t know if they’ll choke on Windows or not – may require some fiddling.)

They require the imagemagick command line tools (convert). Imagemagick may need the settings adjusted in /etc to avoid running out of memory.

They require pdfinfo and pdfunite and pdfinfo utilities from the poppler package/library.


ams_dumplargepdf.py : Dumps a pdf to image files in a directory named after the pdf file.

ams_dumpallbooks.py : Iterates over all pdf files in the directory it is called in.

ams_bindbook.py : takes all the image files in a directory and creates pdf fragments in stages. The pdfunite is called to concatenate all the pdfs into a new bound pdf. (Warning, it will name the pdf the same as the directory name: shuffle the files around to avoid an overwrite.)

ams_bindallbooks.py : takes all the book image directories and makes pdfs from them.

February 2021 Machine Shop Adventures

I recently bought some stepper motors from Sparkfun. I have two others floating around somewhere – they are of the NEMA-17 type (which specifies the face and shaft dimensions and mounting holes.) Mine are m-3 instead of 4-40 mounting holes, but otherwise standard.

I’ve often longed to do something with these motors – to build tools which can build better tools. My initial attempts to build motion stages involved buying stock parts from McMaster and attempting to 3d print all the connecting parts with a Makerbot Replicator 2X. Unfortunately the 3d printer has only about 0.04 inch accuracy, which isn’t enough to make motion stages that won’t bind, even when just aligning steel rods.

In my quest to become able to build serious tools, I’ve acquired a machine shop. I’m still not sure quite how to “climb the tech tree” from poor tools to better ones (more accurate, more precise). How *did* we get from hand tools to the bridgeport? How do you make something more accurate with something less accurate?

(edit, in response to the comment below: Since trying to build my first stages, I have done a little research on some of the steps in this process. I think one of the first ones involved Maudsley in England creating a lead screw using a self-propelled inclined knife on a flat slide climbing against a brass-rod workpiece. Also the Whitworth grinding proceess (which I’ve used myself on 3 pieces of steel – incredibly tedious) to get flat planes. That gave him a master leadscrew which eventually gave him a lathe, which gave some degree of positioning accuracy. I’m not surprised to see interferometry in there. Still haven’t read up on how they managed squareness. I’ll have to watch more of Dan Gelbart’s videos, since he’s been through the process I’ll eventually want to go through.)

Anyway, step 1 would be to build some motion stages so that I can build a CNC thing. (I’m thinking small, high-RPM/low tool force carbide bit CNC mill or something…)

Pencil scribbles

I am not my grandfather. My grandfather could do beautifully fine hand-drawings with drafting tools. I’ve inherited this old map of his alma-mater, Tri-State College done by him during a course on engineering drawing (will include eventually). Thomas French, Engineering Drawing – it was tucked into his textbook.

Hand drawings are useful: They’re faster than CAD when you’re still trying to figure things out, and may be entirely sufficient to plan out a part. Here is that hand-drawing cleaned up and colorized for visual interest.

The big idea

Anyway, this was the plan. I ordered a bunch of stock parts from McMaster, I made one attempt last week to cut the dovetail slide from a piece of aluminum. I figured, aluminum is softer. I can practice on it without blowing up my tools. That worked until I attempted to use the dovetail cutter. Advancing about 50 thousandths per step (way too fast), without using adequate lubricant (Dad suggests WD-40 when cutting aluminum. *Not* when cutting steel – then it would carbonize and work-harden the part.), I ended up blowing up the dovetail cutter in my face.

Aluminum doorstop that also handily stabs you

I decided, since getting the part to that state took 5 hours, to bite the bullet and just do it in steel this time. 5 hours of end milling and a nautical ton (it’s an English unit, honest!) of chips later, I had the slide squared and the square-cuts done with nice surface finish. Can’t feel any roughness with my fingernail (the fingernail test).

Beautifully squared piece of steel, ready for wrecking

I painted some Dykem blue layout fluid on the corner in an attempt to see my cuts.

The wax goop on the tool was difficult to pry off. Tools are often dipped in this waxy crud to prevent corrosion. I managed to get it off by submerging the tool in a pot of boiling water – this worked and allowed me to easily remove the wax, which is important when attempting to get the tool into a precise starting position.

This shows the tool ready to cut. This time I was paranoid, listened very carefully to the horrible noises the cutter made as I advanced, and probably saved myself from a blowup at the very end. I advanced about 5 thousandths per step towards the end, and only about 0.2200 of my planned 0.2500. On the last cut the tool made a horrible racket on the last inch of the cut. On attempting to start the back-side, the tool wouldn’t cut at all. It had dulled itself fairly quickly.

It was a high-speed steel (as opposed to the cobalt steel) 45 degree, 1 3/8″ diameter dovetail cutter from McMaster Carr. (Not sure if I recommend them – they dull too fast.) I’m waiting on a new cutter to finish the job, and some carbide inserts for a 60 degree insert dovetail cutter from Dorian Tool by way of MSC.

One random trick that I had heard about watching youtube videos of people doing far more intricate things: Apparently when cutting steel, you can pay attention to the color of the chips. Straw-yellow means that the chips are getting somewhat hot as you are cutting. If they start turning blue, it means you are work-hardening the part and generating too much heat, and need to proceed (with more coolant, less agressively, at lower speeds).