One way you can figure out thermal expansion of the tools is using the formula
▲L = L * ▲T * CE
Where ▲L is the thermal expansion, L is the length of the tool / part being measured, ▲T is the temperature difference in the measurement, and CE is the coefficient of expansion for tool steel. The CE varies for different steel alloys, but a value of 6.5 ppm/°F is typically used
So suppose you have a 6 in caliper, and the factory floor temperature is 80 °F and your calibration space is 70 °F (a 10 °F difference that needs to be accounted for). Plugging in those numbers you get:
▲L = (6 in)(10°F)(6.5 ppm/°F) = 390 µin.
As you can see the number is small, but it can get significant. Suppose that you have a 24 in caliper and you bring it from the 80 °F factory to your 70 °F lab and you don't let the temperature of the caliper acclimate. then the thermal expansion that needs to be accounted for is:
▲L = (24 in)(10°F)(6.5 ppm/°F) = 1560 µin, or 0.0015 in. As you can see, that is now a considerable error.