I apologize for my lack of mechanical term knowledge. I'm looking for a type of screw I could use in a project. Sorry if the thing is unrealistic or if the part is obvious. I attached a sketch of what I'm looking for. The screw would never be completely out of the hole like the sketch shows, but rather it would be screwed all the way in, and then you would screw it up partially until you get the desired pressure, much like a syringe. Does anyone know what this part would be called aside from a generic screw pump? I would like to use one to attach one component to another with a vacuum seal. The hole size could be about 5 cm in diameter ideally, and the length of the screw would be about the same. And I have a calculation, but I'm more interested in what I've asked about above. Using the 5cm height and 5cm diameter, I calculated the force I would get if the screw starts with a volume in the hole of 2mm height, (2*pi*.025^2)*.002 or 0.00000785 m^3. and is screwed until the volume is at a hole with height 5cm (2*pi*.025^2)*.05 or 0.00019625 m^3. Using boyle's law, with a starting pressure of 101,325 N/m^2 (1ATM), I calculated the pressure after the volume change to be 405 Pa. This gives a change in pressure of 100,920 Pa, and using the surface area of the screw hole of (2*pi*.025^2), I get an applied force of 396N.