Ignoramus6705 fired this volley in
:

Lloyd, so how does it work, the coolant blasts away the chips or just
carries them with a flow? I guess I should try. I need to look into
the pedestal of my mill, there is supposed to be a cooant pump and
reservoir.

My R2E4 has a large coolant tank/catch basin that slides around the base
of the machine. The pump will produce about 30psi at 3gpm. That'll work
two or three 3/8" or 1/4" nozzles just fine.

The "hard stream" is what moves the chips. Not by "pressure", per se,
but by the inertia of the solid stream of fluid. A 3/8" solid stream
moving at (say) 30fps will push a big dimple into the heel of your hand.
Think about what it will do encountering loose chips of all ilk. Even if
they aren't "blasted" from the pocket, the pocket will alternately flood
and be blown out, and constantly re-circulated by both the coolant stream
and the motion of the bit, removing most of the metal on each cycle.

At the injection molder where I worked for a few months, the guy had a
small CNC mill (like 12x8 throws) for pocketing new molds. He had one
1/4" flexi-nozzle (snap-bead style) blasting right at the tool tip, and
it gave elegant finishes. So I suspect chip removal was adequate.

LLoyd