To the workshop!

10 July, 2013

Over in TOG, a group of us have been working on automating this punchcard knitting machine.

Note those two white knobs.

What a contraption.

But then, disaster struck: the machine was accidentally knocked over one night and two crucial bits of plastic snapped off. These two white ‘thumbscrews’ hold the carriage together for knitting, but let you easily disassemble it to remove the all-too-common wool tangles.

How much waste is caused by tiny broken bits of plastic?

These probably haven’t been manufactured in 40 years.

Fix attempt #1: a collection of washers and nuts. Did the job, just about, but was a real pain to undo and redo every time.

Fix attempt #2: sometimes polymorph can remedy situations like this because of its ability to mould to screw threads, but in this case it just got stuck in the crevices of the machine and had to be melted back out with a hairdryer.

Fix attempt #3: to the workshop!

I found a piece of metal in the “teach people to weld” heap of scraps.

Well, easily compared to GRC.

It’s silver, not rusty, and cuts easily. What metal is this?

Having cut a short piece off, the next step was to drill a hole into it. I had trouble drilling the hole central and straight, but Paul showed me a nice trick: stick the metal cylinder into the chuck as if it were a drill bit, then lower it into a vice, secure it, and release it from the chuck.

Thanks Paul!

That’s what a hackerspace is all about.

Nice and central, and ready for drilling.


Please imagine the bottle of cutting fluid in the corner.

The hole needed a thread. TOG only has metric tap sets, and I’d expected the knitting machine to use imperial screw threads because of its age. To my surprise, the thread was metric. Paul thinks it was made in Japan where they’ve been using metric much longer.

Slow process. Maybe the tap was blunt.

Amazing what you can learn on YouTube.

Turn, turn back. Turn, turn back. Turn, turn back. Snap the tap off in the hole, order a new one on eBay, cut a new length of metal and start again. Turn, turn back, turn, turn back…

The drill might disagree.

Maybe I could have used the drill as a lathe?

Finally the thread was cut. The end now had to be shaped to fit the carriage. This would have been much neater in a lathe, but we don’t have one. A file did the job instead.

Yeah, must have been a better way.

The vice might have lost a gram or two there.

Finished! The second one was much quicker to make, and the knitting machine is now back in action. I consider this a small victory against the tyranny of tiny broken pieces of plastic.

I was pretty pleased with myself.


Although, maybe they should be painted a nice 70’s off-white to match the rest of it…


  1. The tyranny of broken bits of plastic is what will bring the modern world to ruin. Dust to dust, ashes to ashes, bits of plastic to broken bits of plastic. Well rescued!

    So, what is the metal? “It’s silver, not rusty, and cuts easily”: sounds like lead but that would be too soft. Aluminium? Not for teaching welding. Must be sodium, yes?

    • Sometimes I wonder what our everyday tech looks like in the parallel universe where we don’t have plastic. My dad has 1940s wireless sets made of wood and metal and glass and cloth and wax. Add 70 years of development, what do you get?

    • Another vote for aluminum. Almost certainly not sodium as it reacts violently with water and touching the metal would leave chemical burns as the sodium would react with the moisture in your fingers to produce caustic sodium hydroxide (https://en.wikipedia.org/wiki/Sodium).

  2. Brilliant job – must be something in the genes…

  3. It’s probably Alumin[i]um.
    Next time you need to tap something, get a lubricant called “Tap Magic”. Squirt a bit on the tap where it enters the hole. Do this a couple of times, as you continue to tap. It’ll cut a lot easier and you reduce the possibility of breakage.

  4. Umm, I realize it is not very hackerish, but those arm (or sinker plate) connecting screws were pretty much standard on all these machines. You can probably find NOS or at least replacements on ebay.

    • Thanks for the search terms! I’ll let Paul know.

      Would you know where we could get a manual for this specific machine? We’re using a photocopied manual from a similar model, which again is mostly standard…

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