The reason it doesn't work good is that you are not using Bernoulli's principle. So, it's not a venturi, or at least a really poor one. Bernoulli says an increase in speed decreases pressure. So you have to accelerate the air at the point of the input. This is typically done by a larger chamber feeding a smaller chamber that feeds a larger chamber. The air in the smaller chamber, where the acceleration is happening will be at low pressure. Use that drill press behind you, and a chunk of aluminum. You can easly get close to a full vaccum.
do you have an idea of sizing? diameters, legths, cross sections of suction holes... i have an access to a 3d printer, wanna make one. made one even multi stage, but i guess its too wide, with too big suction holes, would love an input from someone who has done something similar...
