Variable Gap Magnet

This variable gap magnet is an excellent value. The magnetic field strength at the 20 mm magnet surface is 3950 G and IMO are an N38-N42 grade magnets. I measured the field strength at the center of the gap with a magnetometer for different gaps. The following is the result: 1.8 mm 9460 G 3.3 mm 8180 G 6.3 mm 6650 G 9.2 mm 5300 G 11.5 mm 4500 G 13.4 mm 4000 G 18 mm 2750 G 26.3 mm 1550 G 34 mm 975 G 44.3 mm 580 G 54.3 mm 378 G 69.7 mm 212 G 84.8 mm 121 G IMO if the magnets were changed to N52 grade it should be possible to exceed 10000 G (1 Tesla), not bad for a low cost variable gap magnet. The current magnets seem to be attached to the steel (iron?) screws with epoxy or some other glue. Changing out magnets may be difficult. Turning the gap screws when the gap is small requires some force that is hard on the fingers. To help minimize that force I put some grease on the threads to make turning the gap screws easier.