How Would You Upgrade An Old Ox CNC Build Into A Serious Machine?

[NeoMorph]

The tub provides a thermal reservoir; any heat from the returning water is spread out across all the water in the tub. The greater the mass of water, the lower the overall temperature rise for a given heat input. The larger the surface area of the water in the reservoir, the quicker it'll lose heat to its surroundings.

So, in a nutshell, big reservoirs hold off the need for a cooling radiator.

I understand that... I was pointing out the comments Jazz made about the fact that he ran his spindle WITHOUT pumping water and said it was okay.

What I was pointing out was that if it was “okay” then you wouldn’t need a large tank of water. The fact that many CNC machines do indeed use large tanks of water to sink the thermal energy into point to the need for good cooling of the spindle to ensure longevity and reduce thermal damage to the permanent magnets.