ELI5, How are precision calibration tools, themselves calibrated?

Question

Feels like a chicken and egg senario. Let’s say I get my torque wrench from work sent off to be calibrated, and that’s calibrated with something itself needs to be calibrated, and so on and so fourth. How’s that figured out?

In: 430

Answer 1

at the lab i work at we have a guy from the manufacture(s) come in a calibrate our tools. every 6mo or year depending on tool.

Answer 2

at the lab i work at we have a guy from the manufacture(s) come in a calibrate our tools. every 6mo or year depending on tool.