Overhead fillet welding PD: the T-joint above your head
PD is PB held up overhead: the same T-joint, except that surface tension alone holds the pool and everything surplus falls on the welder. The whole technique comes down to one thing — the pool has to be small.
When PD is unavoidable
When the assembly is already up and cannot be turned: a rib under a beam, a gusset on the underside of a floor, a repair beneath a machine, a joint on a frame already erected. In a shop it is nearly always cheaper to roll the part — in the boat the same weld runs twice as fast and with no burn risk. On site there is no such option, and PD becomes compulsory.
How to run it
Take the current 15–20 % below the flat position and a thinner electrode — usually 2.5 or 3.2 mm. Keep the arc very short: a long arc means a big droplet, and a big droplet overhead falls. Run narrow beads without pausing, straight or with a small weave; a stop anywhere gives overlap. As in PB, the electrode sits on the bisector with a slight bias towards the vertical leg and a 10–15° tilt in the direction of travel.
Guide settings, current 20 % below the flat position
| Thickness, mm | Electrode diameter, mm | Current, A |
|---|---|---|
| 1–2 | 1,6 | 30–50 |
| 1,5–3 | 2,0 | 40–65 |
| 2–4 | 2,5 | 55–80 |
| 3–5 | 3,0 | 65–105 |
| 3–6 | 3,2 | 70–110 |
| 6–12 | 4,0 | 105–150 |
| 10–20 | 5,0 | 145–200 |
| 16+ | 6,0 | 185–255 |
Leg size per run
Nothing above 6 mm goes in one run overhead: the pool has to stay small or it sags and drops. That is half of what the boat allows and a quarter less than PB — the same item takes about twice as long in PD. A leg of 8 mm and up is split into at least three runs, each narrow, with the slag fully removed between them: overhead the slag clings more readily than anywhere else.
What to weld it with
A basic electrode is the best overhead: its slag freezes quickly and props the pool up from below. Rutile spreads and drips — in PD it only suits thin material and small diameters. In MAG the overhead fillet runs in short-arc or pulsed mode on an argon-rich mixture: pure CO₂ throws large droplets, and a large droplet will not hold overhead. Keep the stick-out as short as it will go.
Protection in the overhead position
This is one of the two positions, along with PE, where sparks and droplets fall straight onto the welder. Fasten the clothing to the throat, run the sleeves over the gauntlets and the trouser legs over the boots, and add a neck cape to the helmet. Burns here come not from the arc but from a droplet that found its way inside a collar or a cuff.
The usual defects and where they come from
Overlap and a sagging bead mean the pool was too big: current too high, travel too slow or the arc too long. Undercut on the vertical leg means the arc dwelt at the top. Lack of penetration in the corner means the welder cut the current too far out of fear of the drips — you must not go below the bottom of the range. Pores are more likely in PD than flat: the pool is small and freezes fast, the gas has no time to escape, so clean the edges more carefully than usual and use dry electrodes.
Designation and qualification
PD to EN ISO 6947, 4F in the American system. A test in PD covers PA, PB and PD — three positions from a single test, which makes it a good-value certificate for a shop that works on site. It does not open the butt positions: for those you sit PE or higher.
Frequently asked questions
Why is the current lower overhead?
Because surface tension alone holds the pool. The more current, the bigger the pool and the surer it is to sag and drop. You take 15–20 % off the flat setting and pick a thinner electrode — the same thing by another route.
What leg goes in one run?
Up to 6 mm. Beyond that, split it: three narrow runs instead of one wide one, with the slag chipped off between them. Trying to lay 8 mm at once gives a sagging bead and a lack of penetration in the root.
Rutile or basic?
Basic. Its slag freezes quickly and props the pool from below, which is exactly what overhead needs. Rutile spreads and drips; in PD it is taken only on thin material and in a small diameter.
What does a test in PD cover?
PA, PB and PD to EN ISO 9606-1 — three positions from one test. It does not open the butt positions: for those you sit PE or higher.
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