Helping hand that works

When soldering, you sometimes need a third hand keeping things in place.

I got this idea from the eevblog forum (https://www.eevblog.com/forum/reviews/a-3rd-hand-that-actually-works!/) and the excellent blog post here:

https://www.engineerable.com/single-post/diy-the-best-helping-hands-for-electronics-soldering-pcb-work-jewelry

The thing is, that cheap "helping hands" or "third hands" frankly sucks. 

I'm thinking on the ones that look like this:

 

I've used these ones and the mechanism is limited and the crocodile clips are annoying and don't grip well. You can improve them slightly by adding some heat shrink tube on the teeth.

I do use also other kind of tools, e.g. a regular vice:

This is an excellent vice for the price. The model is RÖHM 863421, and it's perfect for small hobby projects including drilling and cutting.

 I also have this holder for PCBs. It works OK:

 

Now I did have one of these magnetic holder stands for dial indicators. But I hadn't thought of using them for anything else!

They are really nice, because with one turn of the knob, you can loosen or tighten the whole arm mechanism. In addition, there is the magnetic base.

I stumbled upon the previously mentioned links and immediately ordered another magnetic stand. You can find these on the Internet in places like Amazon, Aliexpress and similar.

In addition, I ordered two clamps like these, meant for mounting cameras etc:

Secondly, two 1/4" adapters like this:

I modified the 1/4" adapter, so I could tightly attach it to the magnetic arm:

I had to cut the adapter on one side so that it sits flush on the arm. I made no modifications to the arm of the magnetic stand. Now the clamp could be screwed onto the adapter.

To make the adjustment smooth, and avoid loosening the knob while adjusting the arm (as explained in the above mentioned blog post), you can add an axial ball bearing in between the adjustment knob and the bushing. This is what expensive models have.

I ordered a small axial ball bearing, F5-10m 5 x 10 x 4 mm. 

When adding a 4 mm wide bearing, there is not much space left on the threads for the knob, so it would be best to remove some material from the bushing.

Now how do you do that if you don't have a lathe?

There are always methods available. You can't put the bushing in a drill chuck, for instance. It's so small, so it disappears into the chuck.

Instead, use a screw and a nut:

Now you can put the screw into a drill chuck and tighten down. Measure about 4 mm (same width as the ball bearing) of material to remove. You can slowly rotate and use a caliper or a marking pen. For good measure, put some tape around the bushing also to mark the line where to cut.

Now slowly spin the drill while holding a hack saw onto the marked line on the bushing. I did this in a drill press, but I imagine it will work also with a hand drill. It helps if one end of the hack saw can rest on something. The idea isn't to cut through, but to create a solid groove in the bushing, all way around. If you try to cut through this way, bad things will probably happen (hack saw will definitely start vibrating and ruin it all). Get a half to one millimeter or so deep groove, then stop. Remove the bushing from the drill and the screw and put it in a vice. Cut with a hack saw, while circling around the groove:

Use a file to remove burrs and have a smooth, flat surface.

Now the ball bearing will fit without issues:

Put heat shrink tubing on and you are ready:

Finished product: