Ignoramus12347 fired this volley in
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2) There is no gap between windings and the iron core.

No, Ig... there should be no gap between the windings and the core.

A "gapped" core is where the "I" piece and the "E" pieces are separate,
rather than interleaved. Sometimes, they're even spaced apart a bit
('gapped') to lower the DC saturability of the core.

You saw the windings off flush to the SIDES of the core. You'll end up
with two fairly flat u-shaped pieces, and a chunk stuck in each opening
in the core.

You saw flush to the sides, Ig. Basically face-off the sides of the
core, and you'll have a whole core, and winding chunks left.

Lloyd