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Another version of the 'Third Hand'


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Inspired by Michael Mott’s excellent tool (https://modelshipworld.com/index.php?/topic/14463-restoration-of-bassett-lowke-albertic-by-michael-mott-scale-1100/&page=5&tab=comments#comment-452268 and newer version further down in the thread as well as BANYAN’s review of it: https://modelshipworld.com/index.php?/topic/15249-michael-mott-designed-third-hand/&tab=comments#comment-473797), I decided to put into action something that I had planned to do for a long time. From my late father’s estate I inherited a cast-iron foot that presumably belonged to a some sort of chemical laboratory equipment. Not being impressed with the commercial ‘third-hand’ I kept this piece of cast-iron with the view of converting it into a tool with less and better controllable degrees of freedom. Also just having a pair of cheaply made alligator clamps didn’t add to the useability of that tool that, in consequence, spent most of its life on the shelf. I also inhereted a good quantity of pre-war quality alligator clamps.

 

http://www.maritima-et-mechanika.org/tools/thirdhand/ThirdHand-Hooks.jpg

Third hand with small hooks for rigging work

 

The cast-iron foot was de-rusted and a proper seat for the bar-clamp had to be filed – I could not find a way to clamp the piece to the table of my milling machine. The foot then was primed and painted in my favourite ‘bottle green’ (RAL 6007).

 

http://www.maritima-et-mechanika.org/tools/thirdhand/ThirdHand-SmallJaws2.jpg

Third hand with small clamps in steel

 

Working predominantly in small scales with tiny parts, I sized the tool appropriately. The main bar is 6 mm steel and the two pillars are 10 mm aluminium. I actually prefer steel, but in this case working with aluminium was faster on my small machines. The arbors for all the clamps are 4 mm steel rod. The diameter of 4 mm was chosen, as the alligator-clamps have sleeves that are meant to be pushed over 4 mm-banana-plugs.

 

http://www.maritima-et-mechanika.org/tools/thirdhand/ThirdHand-AlligatorClamps.jpg

Third hand with alligator clamps

 

Thinking about the likely kind of applications, I made a pair of small sprung clamps from steel, a pair of larger toolmaker-style clamps (excellent idea by Michael, btw) in aluminium to be used for soldering, a pair of small hooks in 0.5 mm piano-wire for rigging tasks, and a pair of collect-chucks.

 

http://www.maritima-et-mechanika.org/tools/thirdhand/ThirdHand-BigJaws.jpg

Third hand with toolmakers-style clamps in aluminium

 

The collet-chucks are a commercial products from China with ten collets that clamp from 0 to 3.2 mm. I thought this might be a good idea for clamping wires and perhaps ropes safely without distortion or marring. They were so cheap at 1.50€ for a chuck with ten collets that there was no point in makimng them myself.

 

http://www.maritima-et-mechanika.org/tools/thirdhand/ThirdHand-Collets.jpg

Third hand with collet chucks to hold wires etc.

 

I also plan to make set of clamps from bakelite for soldering, but have not received the material yet.

The thumb-screws are also bought-in, as I have local source here in Paris that sells them for one Euro a piece, which is not exactly cheap, but good value considering how much time I would have spent making them myself.

Edited by wefalck
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Wefalck, Wow! excellent work, it is great to see how ideas evolve and are transferred. I was just asking Johann about the screws with the hole for a bar or pin and see that you have one as well at the base.  I really like the copy of the wood clamp to a steel version.

 

Could you share the source of the small chucks, they look like they would be worth having a set?

 

Michael

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Got the chuck and collets from ebay. It is same as shown by someone in the thread on the pencil drills. The price actually was 2.50 € per piece, but still ... Just search in ebay with "10Pcs 0.5-3.2mm Collet chuck" and go for 'cheapest item first', as prices seem to vary by 100% !

 

Michael, I thought your wooden clamps were inspired by the steel ones, not the other way around ... also tried some in wood, but they didn't turn out well with the beechwood dowels I had.

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P.S. will post a picture of the parts 'exploded' as soon as I get around to take it ...

 

The foot obviously is a one-of antique piece, but I think one could upgrade the cheap commercial ones along these lines, though these feet are a bit small and light.

Edited by wefalck
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  • 2 weeks later...

Rather than bakelite (which is phenolic resin filled with wood flour and which is essentially isotropic) I received ‘Novotext’ rods. Novotext is a composite of phenolic resin and cotton fabric. This is bad and good news. The bad news is that its temperature resistance is lower than that of bakelite and, hence, the clamps cannot be used for soldering as originally envisaged. The good news is that Novotext is much less brittle and more elastic than bakelite because the cotton fabric takes up the strain, as does the steel in re-enforced concrete. The material mill and turns well, and you can cut threads in it. So the design is the same as that for the metal clamps. In the end I got some nice clamps out of it, nicer than the wooden ones I attempted.

http://www.maritima-et-mechanika.org/tools/thirdhand/ThirdHand-TufnolJaws.jpg

 

Third hand with made from ‘Novotext’.

Some people asked me about the construction details and below you find an ‘exploded diagram’ of the tool.

http://www.maritima-et-mechanika.org/tools/thirdhand/ThirdHand-exploded.jpg

Third hand ‘exploded’

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