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A gear that would be inscribed into a 2 threads. Trigonometry and Involute.

Question asked by Tarakan Tarakanich on Nov 12, 2013

I am designing a rather bulky assembly that will be printed on a Filament Fusion Fabrication 3D printer to test out one new engineering idea.


The mechanism will use two screws to either cause a gear to slide up and down. (If turned simoltaniously in one direction)


The mechanism will pivot the gear against it's center. (If screws are turned in opposite directions)

Everything is to adjust a great number of mirrors. This mechanism is not for power transmission.


The gear should snugly fit between the two screws in order for this design to work.

It will have a crossection similar to that of an automotive wheel rim to stay between screws.


view of idea.JPG is a screenshot and it shows it all rather well...


I tried to inscribe a gear between lead screws, based on the tutorial:


I read this:


and I don't understand how it applies to what I am doing.

Too many terms and variables that I cannot connect to real distances, lines and points on my cross section.


The thread is something I designed for a use with FFF 3D printer. It is not standard.

What matters from all the drawings in this case is the crossection and the edges of two lead screws that face each other.

There are three .BLOCK files that offer no means of lining them up.


The parameters of the screw crossection are:

Pitch 1.50MM

Teeth are 0.5MM tall

See file "thread parameters.jpg" in the zipped folder.

There are two more screen shots to describe the problem I am trying to solve.


All surfaces of the threads have a 0.2MM radius fillets.

Distance between screws (top, bottom):




I am not very smart and showing me more tutorials on how to design gears may not help.

I want to know where vaules "5" and "13" came from in the tutorial.



What is being subtracted in step 18?



If my lead screw angle from of the tooth is 116.56505117deg , than how does that relate to the pressure angle?



If you have a tutorial I should see, make sure that it is very easy to understand.

I have a rack (threaded) surface and I am designing a gear to work with that surface.



I can't just pick a gear from the ISO library of SOlidworks and hammer it in place...



It has to be somewhat mathematically accurate because I will have to make about 300 of those parts

and they will be printed on three universities printers for my project.


I am not very good with math. I got through all my math and forgot it for good. I am pretty good at experimenting...

Right now I am home. I need to finish this soon. I would really hate placing a "medeval cog" in there hoping that it will work out.


I know that requires a titanic work to aswer my question. I am sorry. I looked at a lot of gear theory. It is either too hard or too applicational.

Thank you for your help.