[BluesJam]

For my Alnico 5 single coil guitars I link 2 paper clips together and hold them over each pole of the coil.  The paper clips allow me to feel the magnetic pull on the string.  If the paper clip doesn’t touch the string due to magnetic pull, I lower the pickup.  4mm-5mm from the bottom of the string…it appears to be the best setup for me.   Has anyone tried this before?YMMV

[greenlion]

A US Nickel coin held between the string bottom and the polepiece will also get you in the ballpark. They are a tiny bit over 4/64th thick

[BluesJam]

I have used that method in the past.  What is great about the paper clips is that you can visually see and feel the magnetic pull of the pickups upon the strings. With my DiMarzio singles, 3 1/2 to 4mm from the string is the sweet spot.