craftgrrl | question about cutting vinyl

i'm talking about a vinyl record, not the material ;)

i'm trying to do a mixed media collage thingy (my first ever) and it involves using a vinyl record. i couldn't bear to ruin any real records of mine, so i went out and bought some crazy Irish folk records and scottish bagpipe stuff. the thing is, these are super thick! i didn't even realize when i was buying them. they are smaller than a regular LP and larger than a 45. so what would that make them? the huge record store only had oddball stuff in them, so it's not anything i've ever seen before. all the labels say Victor talking machine. and they have that RCA dog. are these 78s? only for phonographs?? a couple are only one-sided. and the grooves are very smoothed out.

i wanted to cut them in 1/2 and glue them to my canvas. but since it's so thick, i'm not even sure what i could use. any suggestions? it's gotta be stronger than a box knife.