Both of these custom vented screws are recurring parts for a research lab we work with.  Measuring 8-32 X 5/8 and 6-32 X 1/4 both are made using Invar 36 material with a vent drilled hole running the full length of the screw.  Invar 36 material has a very low level of thermal expansion and is typically used for applications where dimensional changes due to temperature variation must be minimized as much as possible.  The hex socket drive was broached for both parts, in lieu of a cold headed alternative.