Scroll thread transmission
Scroll thread transmission
(OP)
Greetings!
I am very interested in the theory behind the scroll thread transmission, which is used in spiral ring chucks of lathes. Is there a good description, and ultimately, design rules available sowewhere?
I am very interested in the theory behind the scroll thread transmission, which is used in spiral ring chucks of lathes. Is there a good description, and ultimately, design rules available sowewhere?





RE: Scroll thread transmission
Is this the mechanism you are interested in?
http://www.belarus.net/plant/beltapaz/ki_tap7.jpg
RE: Scroll thread transmission
RE: Scroll thread transmission
RE: Scroll thread transmission
It's just a screw thread (which is just a wedge) wrapped in a different way.
You'll find the fundamentals of screw threads in any basic mechanical design text. Just twist everything around by 90 degrees.
RE: Scroll thread transmission
RE: Scroll thread transmission
Note that the teeth on the back of the chuck jaws have to be relieved on both faces, i.e. made more convex than is ideal, because they have to mesh with faces of decreasing local radius as the scroll is tightened.
Mike Halloran
Pembroke Pines, FL, USA
RE: Scroll thread transmission
Exactly what I meant saying it's not the same as the thread helix. And that's what I particlarily interested in - how exactly do the chuck teeth have to be relieved. Is there any universal solution which applies to the majority of the designs? Or is it more down to the designer?
And do the teeth on the juck jaws also follow the spiral? Or do they derive from the concentric circles?
RE: Scroll thread transmission
Of the chucks I have disassembled:
The teeth follow the spiral.
The teeth within a given chuck differ from one another; the teeth are in different radial positions.
The teeth are always numbered or otherwise marked to fit in a particular location on a particular chuck.
Mike Halloran
Pembroke Pines, FL, USA
RE: Scroll thread transmission
RE: Scroll thread transmission
Mike Halloran
Pembroke Pines, FL, USA
RE: Scroll thread transmission
http://www.cartertools.com/3jawdis2.jpg
http://www.lathemaster.com/images/4_inch_chuck.JPG
RE: Scroll thread transmission
I really can't find any detailed info on spiral transmissions. Although the books that I have explain a lot about all other stuff...
RE: Scroll thread transmission
RE: Scroll thread transmission
RE: Scroll thread transmission
It also shows teeth having one convex face and one concave face, which is representative of a chuck with non-reversible jaws.
Chucks with reversible jaws typically have two convex faces.
Now you should have enough information to make a decent drawing, never mind a sketch.
Mike Halloran
Pembroke Pines, FL, USA
RE: Scroll thread transmission