UniSolder: One-handed soldering with just rubber bands

This is an almost fully printed tool to allow one-handed soldering on the Pinecil without having to ziptie an unwieldy contraption to your perfectly usable soldering iron. Just assemble, load, and spin the wheels to push solder onto the tip of your soldering iron. The wheels are always in contact, so the tool should work with any diameter of solder. 

The only required non-printed components are two ¼ inch wide rubber bands. Any length is fine, and you can probably cut a wider band down to size. 

The main goal of the design is to allow you to solder one-handed only when you actually need to by enabling quick switches between regular and one-handed soldering. If you prefer to always solder one-handed, you'll probably want something more sophisticated. 

For left-handed soldering, print everything mirrored. 

I've also uploaded the Fusion 360 design files so you can design your own attachments/clips. I own only a Pinecil, so the only clip included right now is for the Pinecil. If you design a clip and/or pipe for your own soldering iron, message me and I'll add it to this design or post a remix. The dimensions for the attachment rails(both the inner and outer portions) can be found in the design files. 

Special thanks to the author of this design from 11 years ago for saving me from multiple days of fruitless attempts to coax gears into moving the solder. 

Assembly

Printing

Use 0.2mm layer heights everywhere. Thinner layers bridge too poorly to properly print the dovetails. Any non-flex filament should work, though I've only tested PETG. All the parts can be printed together. 

• Print out the main body, cover, spool holder, spool, clip, wheels, and pipe for your soldering iron
  • You'll get slicer warnings and some parts might come out a little rough, but they'll work fine, even in filaments with poor bridging like PETG. 
• If you have an M3 screw and nut, also print out a stopper block.

Main body

Combine the body and pipe. The bottom of the pipe should be flush with the bottom of the body. The dovetail rails must line up. 

Slide the body, spool holder, and pipe onto the clip. 

Roller assembly

Pull the rubber band through the roller's opening. 

Invert the rubber band so it fits around the roller without twisting. Place the spare length inside the roller. 

Optional: Glue the band into place

You can optionally superglue the band into place. To do this, dip a toothpick(or similar) in superglue and apply glue all around the wheel between the rubber and wheel surface. Let the glue dry fully before continuing assembly.

Push the two rollers together and place both on the axles simultaneously. 

Spin the wheels now. If either rubber band is too loose, you'll see it bunch up against the body, interfering with rotation. 

Apply the cover piece, flat side up. 

Finishing up

Wind solder around the spool and push the solder through the hole in the spool holder and into the hole at the back of the body. Spin the wheels to pull it in until you see it come out of the pipe.

Place the spool into the spool holder. Ensure that the solder unspools from the side with the hole and that no solder is trapped under the spool. 

Optional: Apply the stopper block

To keep everything in place, slide on the stopper block and tighten the M3 screw until it firmly grips the rail. Be careful not to tighten too much, as you may damage the rail or block. 

Slide your Pinecil into the clip and you're done.

To use, grip the iron like in the picture, with your thumb on the rubber grip and your index finger on the far roller.

Happy soldering!