Super Fine Adjustment from Coarse Thread (Differential Motion)

This is model intended to demonstrate a differential motion screw assembly. During design I decided to make it functional for myself, and possibly others, as a handheld clamp for items which need to be clamped and held onto... tightly. The result is crazy! From two coarse screws (one at 10 tpi and one at 13tpi) an equivalent to approximately 44 threads per inch motion can be achieved.

This model uses printed threads but the principle also applies to standard screws off the shelf. Use a standard size socket to turn it or simply an adjustable wrench or pliers, but it does turn well and function using just your hands to tighten the clamp. The clamp force of this assembly is higher than just using one screw or the other, it multiplies the force as well. It pretty much hurts my brain when using it…

If you're interested in learning more about this contraption, there is a video on YouTube explaining everything and comparing this model to a standard screw here:

https://youtu.be/05QRP4C-9oQ

If you feel like making other versions of this possibly from other coarse threads, there is a quick table in the photos section of the resulting motion from one turn of the input screw. Keep in mind that other threads can also be compounded, such as fine vs coarse, or metric vs standard, etc. Let me know what you come up with, I'd be very interested in seeing any other variations made.

I printed my assemblies from PLA and they worked just fine, all parts on this one are Qty (1). This assembly is fully printed and mine snapped together pretty well.

Here is a link to the standard screw threaded clamp if you feel like comparing the two:

https://www.thingiverse.com/thing:6355944

I hope you enjoy this! Thanks for checking it out!

***Update 12-6-23 - the ½-13 internal thread of the large screw has been updated to v1.1 and should now work better… a rookie mistake… My apologies.