Throat
Throat turns up in 2 fields: welding, vacuum. Here is what it means to the people in each one.
Throat in welding
The thinnest section through a fillet weld, from the joint root to the face, which sets how much load it carries.
Distance from the joint root to the weld face. The theoretical throat of an equal-leg fillet is about 0.707 times the leg size; the effective throat used in design adds any credited penetration, and the actual throat is measured on the real profile. Strength calculations use throat area, so a wide but concave fillet can be weaker than its leg size suggests.
"Concave fillet like that cheats the throat, measure it with the concave side of the gauge."
Throat in vacuum
Inlet opening of a high vacuum pump, the flange where gas enters a turbo, cryo or diffusion pump.
Shop name for the inlet of a high vacuum pump, the round opening under the gate valve. Anything that obstructs the throat, such as a screen, a baffle or a dropped part, cuts the effective pumping speed, and anything that falls into the throat of a running turbo can wreck the rotor. Techs compare pumps by throat size because in molecular flow the inlet area caps the speed a pump can deliver.
"Leave the inlet screen in, last time a set screw went down the turbo's throat and it cost us a rotor."