On Feb 9, 3:26*pm, Ignoramus25972 ignoramus25...@NOSPAM.
25972.invalid wrote:
...
I was thinking, right or wrong, that drilling "through" the tube would
not get enough coolant to the bottom. So I wanted to do it by drilling
all holes on one side, then flipping the piece in the vise and
drilling all holes in the other side.

Don't know CNC, 5/8" holes through 1/4" wall square tubing is no
strain on my little Clausing mill at 180 RPM, with brushed-on cutting
oil on inexpensive S&D drill bits.

jsw