At work, I have an American Beauty soldering rig.. It's a auto-transformer connected to the pinchers.
I use them to solder SMA connectors on .141" hardline coax cables.
The cables are good up to about 25 gHz..
I grip the base of the connector (sliver plated alloy) with the pincher probes.
When I step on the foot petal, the current turns the connector red hot
within a few seconds. A ring of solder, wrapped around the cable melts
and flows into the connector body, bonding it to the cable's shield.
It's the little brother of this one..
YouTube - ‪Resistance brazing 3/8 and 1/2" copper tubing, using American Beauty resistance soldering equipment.‬‏