Third...Fourth, Fifth and Sixth Helping Hand

Hi!

Here is a relatively cheap and quick instructable to help you build a useful set of grippers mounted on a simple stand.

You have probably seen, or indeed own, one of those little hobbyist 'Third Hands' - a magnifying glass, and some crocodile clips mounted on a weighted stand, usually used to help with fiddly soldering... or to hold a model steady while you paint.

All in all these things are okay but more often then not I found myself frustrated at the slowly drooping arm, or magnifying glass...or the 'lemon pip' grip the crocodile clips had on rounded objects (that suddenly 'pop out' as you get to the crucial bit of soldering...)

After rectifying and repairing my 'third hand' device, I decided enough was enough and I'd source a better one! Well! You can get these really amazing poseable arm varieties, with a shiny aluminium base, all at a hefty price tag...for what is basically a machinist fluid nozzle and a billet of aluminium. I priced up the individual parts (below) and it all came in under £15, practically half of the online price...and with an hour of making fun FOR FREE.

So here we are, a simple instructable to guide you through making your own Third Hand (plus Ive added a few more hands!)

Step 1: Setup - Tools and Cutting List

All the items are listed out in the images.

The nuts had a coarse thread to them, which meant that I had to recut the threads on the orange bases of the arms. If you get a fine thread nut you won't need to redo the threads!

Everything else on the list should be easy to get hold of. You could replace the perforated aluminium sheet with a solid bar, thick MDF or pine, anything that has some weight and size to it. The idea of this material is to provide a stable base to make the stand from. My next iteration will use a nice piece of aluminium I have ordered from eBay for £3.00. The MDF I used in the photo cost £1 and would have worked just as well!

Tools are minimal, and you could get away without using the knife, I used this to clean up the threads and injection moulded parts of the arms.

Step 2: Detach the Arm Elements

Tricky bit this, pulling off the ends without stressing the arms too much. I found bending the arms into a 'U' shape then pressing a little further made the ends pop off. At this point, if you want a few shorter arms (give the hands a bit of variety) now is the time to pull off a few sections.

I also found, that if you want to use a magnifying glass (I had one left over from the broken Third Hand), pulling off the orange nozzle and pressing in the ball joint from the magnifying glass works really well. In the end, I removed the magnifying glass idea, I'm going to add in a couple of ultra bright LEDs and a USB lead to power a little helper light.

Step 3: OPTIONAL - Using a Tap and Die Set

Because the local hardware store only had a coarse thread nut, I needed to rethread the ends of the arms.

If you don't have a tap and die set, don't worry... just match the thread of the arms with the corresponding nut. Most good (old school) hardware stores have boxes of nuts open so you can see what you are getting. Just take an arm into the store and try them out! That bypasses this whole step!

Take the threaded ends of the arms (now removed) and get them into a vice. Find the corresponding die and carefully recut the thread, ensuring you turn the die set firmly and squarely to the thread of the arm - else you'll end up destroying the thread, and won't be able to fit the nuts on properly!

Step 4: Drill the Arm Holes

I chose the perforated sheet because the holes already existed, and would allow me to line up the top and bottom plates. The small holes are big enough for the PCB mount/stands I had to hand.

Clamping the top sheet only onto the workbench I marked out which holes would hold the arms, and drilled them out the the diameter of the orange threaded parts - roughly 12mm.

I checked each hole after drilling to ensure a good fit.

Step 5: The Nozzles, Clips, and Magnifying Glass

Checking the eBay listing, the crocodile clips are sold as 4mm, checking with the vernier callipers showed they were a little larger.

Using a 4.5mm drill I cleared the nozzles, which allowed the crocodile clip ends to fit snugly. I mixed up a batch of 2 part epoxy and coated both the clip and the inside of the nozzle to make sure there was a good contact for the adhesive to set on.

The magnifying glass used the nozzle in reverse. I found this method meant a tighter connection with the arm. The weight of the glass meant the arm bent severely at the joint, so using this method created a more rigid link to the arm.

I left the arms to one side to cure.

Step 6: Add the PCB Mounts

Using the PCB mounts and screws, with a little Loctite (or equivalent thread adhesive) I set 4 pillars around the edge of the sheet.

I attached the screws to the top section first.

Step 7: Add the Arms

Taking one arm at a time, I pushed the threaded section through the enlarged holes. The nuts were tightened on the underside of the sheet and I used some thread adhesive to lock the threads. I could have used the nuts with the nylon locking ring as an alternative.

Using the spanner/ratchet I tightened the nuts, making sure not to over tighten ... or risk damaging the threads!