We’re checking a machined aluminium housing with a bore specified at 25.000–25.010 mm. Some parts pass the shop-floor check shortly after machining but measure below the lower limit after spending time in the inspection room.
The parts can be around 30°C at the first check; the inspection room is maintained near 20°C. Before adjusting the machining offset, I want to understand whether thermal expansion in dimensional inspection could account for a meaningful part of this difference.
Which temperatures need to be controlled?
Is it enough to let the housing cool, or do the gauge and its setting master also need to stabilise? We use a bore gauge for the recorded measurement and a steel plug gauge for a quick check, so I’m unsure how their different materials affect the comparison.
How would you establish a repeatable inspection method that separates temperature effects from actual bore-size variation?
