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.
Zaggo – what size tap did you use (M4/.7)?
M3/.6
I made one with an M3/.5 and I am not getting great results at least not any better than the pinch wheel pulley. Will try M3/.6 and probably M4/.7.
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.
Aaargh, and it was M3/.5 of course, not M3/.6!
Posted a photo http://www.flickr.com/photos/makergear/4109876726/
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!!