Two hands are just not enough. At least if you want to
solder a bunch of components onto a little developer board.
To prevent you from getting badly burned fingertips or drops
of soldering tin on your carpet, you need a Helping Hand.
A tool to hold the board for you while you can access it from all directions to
put the components on it.
Intentionally designed as a birthday present for our soldering expert Ulf,
it's now a binaervarianz project for everyone.
So feel free to rebuild, upgrade or redesign it.
Searching for parts
While not everyone has a carpenter workshop to search for needed parts, I will
cut down the wealth of detail in my description to the basics. You just need to match
roughly the measurements of the individual parts. I build everything out of wooden boards, but
feel free to use metal boards or plastics.
- a board, approximal 15cm * 40cm, if you use wood, at least 1,5cm thick to add some weight and stability
- 40cm is very long, you could solder your mainboard with it...fell free to shorten
- a wooden strip, 2 by 2 cm, about 75% of the length of the groundplate
- at least 15cm high, as wide as the groundplate, maybe a little bit thinner
- make them at least half the height of the boards you want to solder
- 4 chunks of wood, roughly 4x4x2cm, at least 1 perfect 90° angle
- you could also use metal angles out of your hardware store
- to hold the things together, I used 40mm Torx T20 wood screws..depending on your material,
you may want to use other types
- by the way: I needed 15 of them
- I used two 8x60mm screws and fitting nuts
- I found a metal-into-wood thread that I could screw into the holding arm. This way the tightening screw doesn't wear out the thread
- Of course you can cut a thread directly into the wood or whatever material you are using
- That's a little tricky! You have to find something which you can screw on the tip of the tightening screws to make the actual contact witch the PCB you want to solder.
- I used some cupboard feet, they have a hole in the back, have a spherical joint to move around and are made out of soft plastic, so you can cut a groove in it to hold the PCB
- a bolt....or a nail.....or a screw.....or a pencil....surprise me ;-)
- It needs to be as long as the wide of the rail plus the 2 angles plus some additional length to get a grip on it
- The thickness determines the diameter of the holes in the rail and the angles
Beside the holes for the screws (which can be seen on the picture), you need to drill holes in the rail to hold the fixation-bolt. The space between these holes should be calculated a little bit smaller then the effective range of the tightening screws (lenght of screw minus head minus thickness of holding arms minus nuts minus depth of hole in the holding pads).
Next, one holding arm needs a big rectangular hole to fit over the rail. I used a circular saw and a chisel, but a jigsaw would be the safer tool to use ;-) .
The two supporting angles on the moving holding arm need a hole for the fixation bolt, too. It's crucial that the holes of the angles and the ones in the rail align perfectly, so the arm is firmly fixed and doesn't rattle. You can do this by first mounting one angle on the holding arm, place it over the rail and drill through one of the holes in the rail into the angle, then mount the other angle and again drill through the first one and the rail.
Also make sure that the angles align properly with the bottom side of the holding arm, so the whole moving part has a flat surface to stand on.
If you build it as big as my version, screws with pre-drilled holes are enough. When building something smaller you should consider using less and smaller screws, but additionally glue the parts together. I don't give you exact positions for the screws, you could think for your self of the right points to fixate all parts.
Last thing are the holes for the tightening screws. Normal holes the size of the screws will work well, you just have to use fixating nuts to keep the screw in place. (And you have to lose and tighten the nuts every time you place a new PCB in the third hand)
So I found a metal thread to screw directly into the wood, so the screw intended to be used to fixate a new PCB now doesn't need anymore nuts (maybe just one to make it safer).
The third hand is a nice tool to build as a birthday present. It doesn't involve much preparation, money nor even skill.
But is it usable?
If you build it as big as mine, it's more a nice thing to look at. It's to big to hold tiny one-chip developer boards, but also not strong enough to support the weight of a full grown ATX motherboard (what to solder on this anyway..).
If you build it smaller, it might be useful, but you have to improve some minor things like the holding pads.
For small components a desktop-note-holder (a alligator-crimp at the end of a gooseneck support) would offer faster results.
But don't let that bring you down! Start working on your own version, maybe you find some better solutions than me. Have fun....send pics ! ;-)