Downloads
They Like It
Helical Crayford Focuser - v2 by Buback is licensed under the Creative Commons - LGPL license.
© 2011 by Buback
Instructions
Print 6 petals, 1 Focuser base, and an eyepiece lock (which you might want to redesign to fit your tube, so source your tube first).
Assemble as in the pictures, except use smaller screws :-). Everything is M4 except the M3 on the eyepiece screws. I think m4x30 is a bit conservative, and you might be able to use smaller, like 20-25mm. In the pictures of mine, i used 40mm 'cause that's what i have on hand, but there's at least 15-20mm extra.
You might also like a focus tube lock, and if so print out one lock petal and only 5 petals, replacing the 6th petal with the lock petal (only in the fine pitch for now)
There is a base plate for a 6 inch tube like a PVC drainage tube, and one for a truss like design, which has a flat bottom face. The truss base plate is more multipurpose; it can be used on all sized telescope tubes and trusses. You just need to print an adapter to attach it to, so i would recommend the truss design.