Harold point of information.
. ” 3/4-inch tube, actually about 7/8-inch in outside diameter depending upon the schedule or wall thickness, could pass comfortably through a 1-1/4-inch hole”
The “Schedule” of type K, L or M tubing all have the same outer diameter BUT the internal area varies as M has the thinnest wall thickness then type L then K
Now for something even more interesting re copper heating applications
A lot of tubing failures can be directly attributed to poor system designs like excessive velocity with too high a temperature.
2-3 FPS @180 degrees Max
A lot of helpers not knowing why these systems fail constantly blame it on thin wall tubing and these apprentices being silly in the mind install a heavier wall tubing thus compounding the problem even more with creating even more restrictions go figure.