Trevor Thompson wrote: ↑Thu Mar 09, 2023 12:04 pm
Oh matching screw threads - how did you do that?
I was doing some work for an acquaintance, just printing project boxes for him. Part of his work involves a small lens focussing onto a photodiode on a pcb and he asked if it would be possible to print some sort of screw focusing mechanism. I said I'm sure it's possible but no idea how to actually draw a screw thread, let alone how printable it would be.
Anyway, a quick search came up with this Youtube link:
https://www.youtube.com/watch?v=k8AC5LNMo-g
...and to my amazement, not only is the video really easy to follow but it actually works! Took me several goes to work through it and get the steps into my poor brain but the result is perfect for what I needed.
Basically I needed a 22mm ID tube with a screw thread on the outside face, and a 3mm thick plate with a matching internal threaded hole, and to get 2 or 3 threads on the inside of the plate hole.
I followed the video to get a solid screwed rod and then used the scale tool to push and pull it until I had the threads deep enough to get 3 in the 3mm plate i.e 1mm pitch. Then I drew a 22mm diam circle on the end and pushed it through to get the hollow cylinder.
I duplicated that and saved one copy, out of the way to avoid accidents.
I then constructed a box to completely enclose the hollow threaded cylinder and checked to ensure yhat the top and bottom faces were all coplaner ( had to use "intersect faces" to be sure). Then I deleted all the internal geometry and that left me with an internally threaded hole in a block. This thread of course exactly matches the original one so there is no way they would slide inside each other, so I scaled the block slightly in the horizontal plane to make it approx half the thread depth larger diameter.... hey presto!
Screw thread as constructed - compressed to the right pitch - matched threaded block
- Screenshot 2023-03-09 13.15.28.png (55.66 KiB) Viewed 3461 times
And this is the end result ( ignore the gap, I made this one too tight and had to cut it off
):
- P1010019.jpg (256.06 KiB) Viewed 3461 times