"Third Hand" for Soldering




Introduction: "Third Hand" for Soldering

About: I like building things, and teaching people to build things [although more of the latter than the former. This came up at the hackerspace the other night. Helping people with their projects just means I ge...

Every third hand I have ever used has been really terrible. I've heard that coolant tubes (used in machining) make great third hands (they don't move around once you place them, and you can place them anywhere, at any angle, in 3D space).

I looked online, and sparkfun (who I love), sells a third hand that takes advantage of this (yay!), but theirs is just a rectangular plate with some threads in it.


We can definitely do better!

Today I'll show you my version of a third hand. It was made as a gift for a good friend of mine (sidenote: flate rate shipping boxes from USPS are awesome! This thing ended up weighing a TON, but it was still cheap to mail it halfway across the country).

The "body" of the 3rd hand here came from some remnant stock I picked up at my local metal supplier (been sitting on the scrap shelf in the lab for at least a year now), and the head and legs (bolts and nut) came from a really awesome scrap yard in Phoenix called Davis Salvage (the only place I know of in town that still lets people dig through scrap).

I built this at Heatsync Labs in Mesa, AZ. If you want to come there and build something like this with us, come over! We have open hours almost every day of the week! (come in and use the lab: as always, it's free).

Step 1: Gather Your Materials

Here you can see the base materials that I'm going to work with layed out here. Not pictured are: the alligator clips I used for the "hands", and a heatsink that I cut in half for the mohawk!

Step 2: Sketch It Out

Put your materials together and figure out an aesthetic that you like. I found that having my robot-figure "sitting down" was a LOT better than having it standing, because if it was standing it was really top heavy.

Step 3: Mill Some Holes for Threading

The threads that I used were #14-1.5. I didn't know this until I started, and figured it out by threading one of the dies from our tap and die set over the thing I wanted to bolt in.

Consult your tap-and-die set for a drill-size. For size #14-1.5, I needed a 1/2 inch mill.

I plunged a .5inch deep hole into my piece for this. This gave enough room for my hoses to thread into, as well as some "run out" space for the tap (I'll explain in the next step).

Sidenote: here is a great chart of tap:drill sizes: http://www.carbidedepot.com/formulas-tap-metric.ht...

Step 4: Tap the Threads!

Tapping threads is REALLY easy, just make sure that your tap starts out straight.

I used a little thread cutting oil for this. To do it, get your tap, put it in the hole, and twist! Super simple stuff!

A tip for tapping: your hole needs to be a little bit deeper than what you actually need to thread into. Keep in mind that your tap is tapered; it starts out not very aggressively cutting threads into a hole, and gradually tapers up to your full thread size. Give it a little extra room at the bottom to account for this.

Step 5: Clean Your Materials

I said in the intro that I got these bolts/nut at a scrap yard. They were COVERED in corrosion, paint, and gods knows what else. Get that nasty stuff off of them, ESPECIALLY if you're going to be welding them.

No questions here: gotta clean these up.

Wear a respirator when you're grinding. One time I didn't wear a respirator (don't need no respirator!), and the next day, I found some grey slurry coming out of my nose. GROSS! I learned that lesson!

You don't want to breathe old paint and corrosion into your lungs, let a cheap-o respirator catch those particles instead.

I started off by cleaning these up with a bench grinder, but it was taking longer than I wanted, so I switched to a wire brush mated to an angle grinder. The metal brush worked a LOT better, although seeing clouds of old paint and corrosion poofing off of them every time grinder met bold was a solid reminder about that respirator

Step 6: Weld Everything Together

I don't have a picture for this :(

Weld your bits together. On our machine, I used maximum current (there wasn't a setting for 2" square stock, haha).

Step 7: Combine Alligator Clips and Tubes

These alligator clips fit perfectly into the slots at the end of my coolant hoses. I smashed them with a big pliers to get them flat, then super glued them in place.

Super glue worked great. Really, really strong hold on these, I don't think they're coming out any time soon.

Don't get superglue on your hands!

Step 8: Admire Your Work

Yay! It's all put together, and it looks cool! I wanted mine to have some extra coolness on it, so I headed to our tear apart bins and cut an old heatsink in half. It looked really cool as a mohawk (mohawks are ALWAYS cool.)

(Last picture is proof that old and new can still be friends)



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30 Discussions

Can't help how adorable this is.

I really want to make it but I don't have a workshop. Any chance I could somehow use superglue? Or something else to get around it?

1 reply

I think you could do it with superglue, probably!

I would recommend getting some nuts for the hoses to thread into, though, and then gluing those nuts to the side instead of the hoses themselves. I think that otherwise the hoses would break off of the metal.

A quick question, how steady are those coolant hoses? I mean is it too easy to bend? I been looking for something things like that for a LED project

5 replies

Thank you kindly for the reply because it will be really handy to mount a few led on the end of it to make a flexible soldering light or use for some close up photography.

That's a really good idea! I wonder if you could get the lens out of a small flashlight to put in the end... ?

I posted a reply earlier and I changed my mind, lol. OK, a flashlight produce very harsh lighting, it would be much preferable to have diffused like source. A 24 SMD G4 light like the first picture would be very easily mounted at the end of the coolant hose.

The second picture is a PIR LED light I made using superflux led power my a 5V 18650 USB bank, You won't need to PIR part but If you want portability it is simple enough to make. I use sticky copper track to carry the power instead of cable.


Found the ideal light for this.
If you search "usb 18 led flexible light" on ebay, you will find it. I am not sure how bright it is my order has not arrive yet but I seen video on youtube about it. USB or battery powered, there a few versions some has a 3x magnifier in the center.

18 led usb light.jpg

Good idea, I can reuse such tripod: http://joby.com/gorillapod/hybrid (it is not the original one, therefore the quality was not the best)

3M calls it a respirator...


An N95 is considered a respirator, and is certified to a NIOSH standard (specifically that it has a Particle Filtration Efficiency of >95% with particles down to 0.3 microns in size). Although nuisance dust masks look similar to N95 respirators, dusk masks should be considered worthless for anything other than keeping paint chips out of your mouth.

If you want to get technical, blhack also isn't using his N95 respirator correctly, because his beard is interrupting the seal between his face and the mask. Unfortunately, the only solution besides shaving would be to use a positive pressure hood-type respirator, which would be expensive.

If you want to get really technical, you should also worry about all of the tiny dust particles settling in your work space and then getting stirred up the next time you walk in (without your respirator on). And for the ultimate in paranoia-inducing information, go read Bill Pentz's website, which explains how extremely fine dust (from woodworking) apparently ruined his health. Not everyone has such a bad reaction, but it's good to know the risks so that you can decide how much caution is reasonable in your situation. Personally, I just do all my dusty work outside while wearing a respirator.

I think I can answer that, it is called coolant hoses, there are many types ofc, so if you search "coolant hoses cnc" you will find them.

I was asking in earnest. i'm not familiar with sanding corrosion that much at a time, and wondered if a regular ol' dust mask would suffice. instead of having to ask the question later, I showed pictures to remove any ambiguity.

Nice instructable and thanks for sharing. I'm definitely building one but it'll be a mutant one with three arms.

1 reply

Cool! I'd love to see a picture of it when you do! :-D

My next one is going to be a squid with 8 arms, bwahahaha :-D