Joe, Boye 21s (at least the ones made after 1925....that's when they changed #s) are flat shank needles. I've been buying them for years for a couple of my National machines. Either yours are in the wrong tubes...unlikely if you've got 3 tubes & they're all alike....or yours were made before 1925 when they changed their #s & a 21 was a round shank prior to 1925. Here's the ISMAC flat shank needle chart
http://www.ismacs.net/needle_and_sha...lat-shank.html
At least some of the machines on your list use a flat shank needle....I know Reversews do.