You pick up a magnet and see if it passes through, say, the middle hole. If it does, see if it passes through the next smaller hole. If it doesn't you've got your bin size. If it doesn't pass through the first hole, try a bigger hole.
Since you can't line up the magnets side by side to compare them since the magnetism miss aligns them, I would take a piece of wood about 1" thick and drill a row of holes through it the diameter of the magnets. I would then saw it in half through the holes, leaving about half the hole in one half and throwing the other away. I would then get wooden dowel the size of the magnets (or carve scrap wood) and glue short pieces into the grooves created by the holes - inserting the dowels in the right position so each groove holds one length of magnet with its end even with the outside of the block.
Like the metal template idea but cheaper - a magnet placed in a groove will either be exact length or short or long. Exact length, drop it in the bin or box for that size, short or long swap to right place.
Lay down a flat base, like plywood. glue down a piece of aluminum angle stock so it has one leg standing up and the other leg to the right.
set down another angle stock with the legs up and left. make the space between them taper so the wide point is up or away from you. The narrow end is near you.
the wide end is larger or farther apart than .800 inches. the narrow end near you is narrower than than .640 inches. Mark lines on the upright legs at the increments of the various lengths with a peramenant felt tip pen. The bottom legs are outward so they don't interfere. scratch marks into the aluminum with a scribe and darken it with the pen. Slide a magnet down until is touches both sides at a line marked with the size. Aluminum is more rugged than wood unless you use hardwood.
aluminum is no ferrus so is wood. Aluminum will not wear.
How about weighing them on a $20 digital scale ?
(actually I'm having a hard time visualizing a real manufacturing company in the 21st century paying someone for a month to sort magnets by hand)
I work for a company that deals with cylindrical magnets. Some days I would sit there with a caliper and measure each magnet lengthwise (sizes are .780, .720, .690, .665, and .640 of an inch, so it's hard to eyeball it) and drop it in its respective bin. The thousands of magnets I would have to sort through would literally take me a month to finish, and it is a long and cumbersome process. I am trying to think of a way to sort them quickly, but each method I come up with seems to have flaws. I want the mechanism to be simple and cheap enough to make by hand, nothing that requires electronics or hydraulics, etc that manufacturing companies use. I have access to wood, so I can build it out of wood. Anyone have any ideas?
