Welder's Third Hand

This photo shows a couple of welder's third hands (or should that be a third hand and a fourth hand?!) that I have made to help holding parts together prior to tacking them in place with a welder. The parts they are holding down in the photo are purely for the benefit of the photo and the t-nut in the middle is entirely irrelevant.

The body of each third hand is made from 38 mm diameter EN1A. It has an M8 threaded hole centrally in one end and two M8 threaded holes 26 mm apart on the other end. The "finger" that holds parts down is made from black mild steel round bar. It was threaded on one end M8 and the other end was machined to a taper. It was then put in a bench vice and hit with a club hammer until it was at about 90°. An M8 nut was screwed onto the threaded end, the finger was screwed into the body and then the nut tightened such that the finger was at 90° to the axis of the rear threaded holes.

Two lengths of M8 threaded rod are inserted into the rear threaded rods and held in place with nuts. The block visible in the top-left of the photo is 18 mm × 11 mm flat bar (a strange size, but it's what I had). The threaded rod passes through two 8 mm holes (26 mm apart) and there are two more 8 mm holes in the other face. These have M5 tapped holes aligned with them for fixing the legs in place.

The legs are again made from 8 mm black mild steel round bar. A flat has been filed on one side for the locking screw to bear onto and they've been gently rubbed with a sanding belt (hence the slightly stripy finish) until they pass smoothly through the hole.

In use the legs can be adjusted to any required height (possibly by replacing them with longer 8 mm diameter bars) and the finger placed on the workpiece as required. The adjustment of the leg length helps ensure the force from the finger acts in the right direction; the weight of the 38 mm diameter body provides the required force to hold the work down.

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