How to Build a Modular 3rd Hand for Welding

  • By: Monica Shulz

Holding an object in place while welding can be difficult, especially if the object is something small that can’t be clamped. This can lead to slips and unsightly weld lines.

To help you hold these objects, we will show you how to create a modular third hand for welding. This simple tool will help you keep objects in place with its weight while you join them with neat welds.

What You’ll Need

You’re going to need a few items to build this modular welding hand. They include:

  • An old drill chuck
  • A 12mm round stock bar
  • A bolt

Once you’ve gathered all these, let’s start building the tool.

Cut The Base for The Modular 3rd Hand

Clamp the 12mm round stock bar upright using a bench vise. Measure a 20cm section from the bar.

Using an angle grinder, cut off the section from the bar. Make sure you wear safety glasses to protect your eyes from sparks while using the angle grinder.

Bend The Bar

Take the bar section you just cut and mark a point in its middle. Insert the bar into the bench vise and clamp the vise on the middle mark.

Using a mallet, tap the bar until it bends around the teeth of the bench vise. If you have an acetylene torch, you can use it to soften the middle of the bar to make it easier to bend.

Continue bending the bar until the angle between both legs is about 60 degrees.

Chamfer The Base’s Legs

For the Modular 3rd Hand to be stable, we need to cut a new edge on its legs. Place a meter rule on the workbench and makes sure it’s perfectly straight.

Place the bent bar directly on the meter rule, ensuring both legs are perfectly aligned on the ruler’s edge. Using the ruler’s edge as a reference, mark a line on both edges.

Clamp the base in an angle grinder and cut both legs at the marked sections. Now, the base should be able to stand on a flat surface.

Join The Drill Chuck and The Bolt

Clamp the drill chuck in the bench vise, ensuring the collar (the hole the machine spindle enters) is facing up. Insert the bolt into the collar and screw it in until it is screwed tight and cannot turn again.

Using an angle grinder, cut off the head of the bolt.

Join The Drill Chuck to The Base

With the Drill Chuck still in the bench vise, place the bent section of the base on top of the bolt Support the base’s legs with a couple of magnetic squares to keep the base in place.

Using a spot-welding machine, join the bent section of the base together with the head of the bolt. Remember to use eye protection when welding.

Also, remember to weld both sides of the joint to make sure it’s strong.

Cut the ‘Finger’ For the Hand

Take the 12mm stock bar and make two marks, 12cm and 20cm from the end, respectively, on it. Clamp the bar in the bench vise.

Cut the bar about 5mm away from the 20cm mark using an angle grinder. Leave the cut section in the bench vise.

Shape the End of The Finger

With the bar still in the bench vise, use the angle grinder to create a chisel-like edge. To achieve this, cut off a triangular section from both sides of the bar from the end to the 20mm mark.

Bend The Finger

Remove the finger bar from the bench vise and re-insert it vertically. This time, clamp it on the 12mm mark.

Using the mallet, bend the finger around the 12mm mark. Continue bending it until you have an angle of about 150 degrees between both sides.

Join The Finger to The Drill Chuck

Remove the finger from the bench vise and insert it into the jaws of the drill chuck. Make sure you insert the other end, not the chisel-shaped side.

Using the drill chuck’s key, tighten the jaws around the finger until it is firmly seated in the jaws.

Now, the 3rd hand is complete.

Clean and Grind the Modular 3rd Hand

Using a grinder with a wire brush wheel attachment, clean the surface of the modular 3rd hand. Make sure its surface is free from any rust or any other impurities.

Also, grind down the welds to ensure the welded joints are neat and flush with the surface.

Final Product

So, that’s it; we’re done building the modular 3rd hand. You have a highly functional welding jig that can help you get clean, accurate welds.

A great part about this jig is that you can always modify it by removing the finger and adjusting the bending angle. This way, you can use it for workpieces of different sizes.

For tips on how to make more useful jigs like this one, you can check out the Bad Decision Works channel on YouTube.

Photo by Bad Decision Works / CC BY 3.0