First Fruit

Today I went to the local steel dealer and bought some metal to play with:


Mostly brass rods and some square aluminum rods (I already had the piece of round aluminum rod from an earlier project).

So what to do with a bunch of metal, a brand new lathe and practically no experience?

Well, I tried to fabricate a threaded pulley as seen on Nophead’s Hydraraptor blog resp. aka47’s blog.

To my own surprise, only 3 hours and a broken M3 tap bit later, I held the finished pulley in my oily hands:


I’m still not sure why the tap bit broke. Probably I advanced the pulley too far in one step. Oddly enough, the tap bit broke after I finished, when I decided to let the pulley revolve twice without advancing it any further.

Anyway, it was really fun and I’m still amazed how easy it was.


  1. What diameter does your pulley have?
    I turned the one I’m currently using in the Printruder from a 12mm brass rod (see image above).

    I didn’t make any measurements, but I didn’t have any slip issues yet (which I had on a regular basis with the timer pulley). First and foremost, I never had any stripping issues with the threaded pulley (which I had several times when still using the timer pulley and trying to fix the slipping issue by tightening the pulley/idle wheel gap).

    So, without having proven this with a scientific test (force measurement or something), my experience is that the threaded pulley grips the filament at least as good as the timer pulley, but doing this a lot more reliable and far less damaging the filament.

    I try to do some better and more “numeric” tests on this soon.

  2. Posted a photo
    It is 0.5 inch (~12.5mm) stock. M3/0.6 is a good idea. Might give it a try.

    I used a cheap tap to make this (in case I broke it) but don’t know if my nicer tape will make a difference (and I don’t want to break it!).

    The filament is moving nicely through the pulley and idler wheel and getting good traction. It does not slip if I pull it by hand but I have not done any metered measurements either. Just trying to find something that works!!

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