Something seems a bit off in a couple of statements about the laminations being insulated from each other in transformers. Every EI transformer I have ever cut open had the I welded to the E unless they were EIEI meaning the E parts were interlaced with the I's filling the voids then bolted or riveted together. Never have a seen a transformer that had the individual laminations insulated from one another in any way shape form or fashion not even varnish.
It is correct however that factory made magnetic chucks used a lot for holding parts on a surface grinder have what appear to be separated laminations with magnetic and nonmagnetic materials. generally, these are made of made of FE-Si steel with stainless sandwiched between them pressed tightly together and welded around the perimeter to prevent separation then ground on all sides magnets are then made up in a pack with Seperators corresponding in the same way the chuck table top is laid out to switch the magnet off there is a lever which moves the magnet pack out of alignment Other chuck tables which may have both permanent magnets and electro magnets in them use the electro magnets to release not for the holding. Then there are pure electromagnetic chucking tables where it looks like the coil is a copper bar woven between the laminations in a continuous zig zag pattern from one end to the other.
I have 2 6inch diameter electromagnets that are made out of a solid bar trepan bored with a coil potted in the cavity they have about 600 lbs pull each using 120vac @ 6 amps
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