Mar. 27, 2015 | By Alec

It might be that I’m just not the handiest of guys out there, but surely I can’t be the only one out there that could’ve used an extra pair of hands when building, repairing or assembling something. An extra hand to hold those parts together, an extra hand to hand you that one screwdriver you need. If this sounds familiar to you too, then this Robotic Third Hand could be just what you need.

As you can see in the photos, this Robotic Third Hand has little to do with the 3D printed prosthetics you often see. Instead, it's essentially a device worn on your wrist that holds tools for you – in this case a screwdriver. When that inevitable moment occurs that you need to screwdriver at an awkward moment, you can simply press a button and the tool is thrust into easy reach. While we could claim that it’s an essential tool for any tinkerer, it is above all a fun tool that can make tinkering more fun.

Designed by engineer Tim from Rochester New York, this Third Robot Hand was designed as an entry for the Hackaday Everyday Carry Contest. As Tim explained on his Hackaday blog, it was something he was meaning to build for quite a while and this contest seemed like the perfect opportunity. While it was quite a project from start to finish, as Tim ran into a few problems and surprises in terms of money (taking a total of five iterations), it is fairly easy to recreate yourself as Tim has kindly made all the files and code available for others to use.

As Tim explains, the Robotic Third Hand revolves around a Trinket Pro, which acts as the wristband’s brain. Aside from that, you’ll need a few other electronic parts and obviously a tool for the hand to hold: a 9g cheap hobby servoTower Pro SG90, one 5V boost supplytakes single cell lithium battery (3.7V, boosted to 5V), one 300mAH single cell LiPO and a good, thin magnet. ‘If you were going to use a Power Boost 1000 then you'll need to adjust the size of the hole that made for the supply,’ Tim adds.

Aside from that, download the 3D printable files Tim has provided on Thingiverse here, and print them. Tim himself used his own UP! Mini 3D printer, though a comparable (prerferably bigger) machine will do just as well: ‘I think it’s a fantastic printer, but it only has a roughly 4" print bed, and this contraption was a little more than 5" long,’ Tim explains.

Assembly itself is pretty straightforward, though you’ll have to find your own way around the parts as Tim has not provided us with a guide. He just adds this word of warning: ‘As you are assembling the 3D printed parts you will notice that all the screw holes are either slightly under sized or oversized. The 2-56 screws will self-thread into the under sized holes and spin freely in the oversized holes. This allows the screw to securely hold the screwdriver tray while the arm that actuates the screwdriver tray can move freely. If your parts aren't going together like that then you either need to adjust your printer or adjust the sizes of the screw holes. If you are printing on UP! Mini you should have no problem, that's what I printed everything on,’ he explains.

Once assembly is done, it's a matter of programming your Trinket Pro, for which Tim has graciously provided all his code already you can simply copy-paste it from here. Now strap yourself in and have fun with it! As you can see in the clip below, it works just fine.



Posted in 3D Printing Applications


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