Temperature does affect metal, but most intruments made are not that close in tolorence to worry about.

When I was much younger and worked in a model shop all the technicians in the inspection department, wore cotton gloves not to keep their hands warm, but as Miller said to not increase the size of the objects being measured. The room was also climate controlled. Some of the dimensions were to very close tolorances and were measured using an optical comparator, which can magnify the object quite a bit for measuring.

David