I know how a welder works.
My point was how do you call a circuit with a 50 amp plug in it just a welding circuit and get away with undersized wire for the breaker? If the welder can be unplugged it isn’t a dedicated circuit. It’s also ridiculous to buy a 50 amp breaker and skimp on the wire for the small added cost.
Under most codes a circuit is built up of breaker, wire, wiring devices/outlet. Under most circumstances the wiring devices/outlet is allowed to be bigger than the rest of the circuit, as it is protecting itself and the building it is in.
Most older stove outlets were a 6-50 and they only had eight gauge wire. The wall mount wiring devices/outlet could handle 50 A. The breaker was 40 A sized to the internal wiring.
Now a lot of stoves have 14–50 wiring device/outlet. The breaker size is most often still 40 A with eight gauge wire.
If you run six gauge wire from a 50 amp breaker to a wiring devices/outlet 6-50 or 14-50 The wire is actually 10%ish oversized(copper). Aluminum I am assuming we’re not discussing.
In all circumstances (except for welding circuits,)the breaker needs to be adequately sized to the building wire.
Some heat treat ovens come with A wiring devices plug 6-50 and some shop heaters come with the same line device.
I personally do not advocate using smaller wire to get you by on a welding circuit. I feel if you’re putting in a 50 amp breaker, put in six gauge wire. If you’re putting in a 40 amp breaker put in eight gauge wire. If you’re putting in a 30 amp breaker put in 10 gauge wire and change your wiring device to 6–30 or 14–30.
I do a fair bit of TIG tool welding in my residential Machine shop. Attached building. I have four different circuits from the main powering the same shop. Hopefully one day I’ll pull the fifth to isolate lighting from the main.
Here are some more food for thought. I only have a 55 kVA transformer feeding myself and four other neighbours. I get one neighbour that knows what I’m doing, asking if I was pulling A lot of power during the night. They saw their lights dim for a few seconds a couple times. Yep that was me. I’m still running a low volume machine/pattern/wood shop in a residential area. I’m not an angel at any means. My code specifically says to a Teee...”No Outlet is allowed to have more than 150 V to ground disbursed... in residential. oops... I have a at least a half dozen 600 V machines.
I also have about a half dozen machines running on pulse wave modulation (or VFD)... but that’s another story.... nobody realizes how easy it is to put out of date, industrial equipment that is three-phase into a residential situation. Clickety click Barbara trick.
I am now a professional educator with shops on the side. I personally wish our youth were willing to learn A task. I am completely saddened that are today’s youth does not even know how to use a handrail! But they can show you how to use the next gaming system on daddy‘s iPad. Sorry for the rant.