The only thing I hate about 3D printing is the obsessive compulsive nature required for leveling the print bed. As a woodworker I use jigs for everything and today it occurred to me to use one for the x-axis. Use a short piece of wood say 64 mm (about 2 inches) long to level the axis on both sides. Now without having to determine whether or not your eyes are failing because you live in a state that condones marijuana use you simply have to place the bottom of the wood piece on the aluminum part of your build tray, then turn down the drive rods until the 500 mm smooth rods of the x-axis touch the wood firmly without pushing down the aluminum plate below.
Do you remember 7th grade when the science assignment was to measure something with a yard stick and no one had the same measurement? This should take out the guess work. I realized this when I was printing 20 mm blocks. I am at an age where my vision is a bit slow but If I simply cut a 20 mm or so block and place it under the nozzle, I can adjust the build plate up or down as required. I can do it on both the two rear corners and the two front corners. Viola!
I have found that the thickness of business cards can vary from 0.27mm to 0.33 mm so unless you keep the same business card it will be difficult to achieve the same distance between the build plate and the nozzle. A feeler guage works very well but judging how tight the nozzle is pressing down on the build plate can be somewhat non specific. Using a block of a specified thickness which you know and lowering the nozzle to the block from either the LCD screen or the slicer 1mm at a time should give the perfect space from the build plate when the block is removed and the machine is homed-all. It should be an easy peasy to adjust your PEI sheet up or down as needed at the corners of the build plate and a level x-axis.
If someone wants to tell me that my idea is stupid I will take the criticism. Being wrong is a great way to learn. On the other hand I would like to cut down the time it takes to level my bed. Don’t we all have better things to do?