What size water tubing fits on the spindle?

The spindle water inlet and outlet fittings are 1/4 Inside Diameter and 3/8 Outside Diameter. You can find the silicone tubes here: https://buildyourcnc.com/item/pneumatic-hydraulic-silicone-tubing This fitting will connect to the pump (1/2" male to 1/4" female): https://buildyourcnc.com/item/pneumatic-hydraulic-Tube-Fitting-Female-to-Male And this fitting will provide a reduced barbed size (1/4") for the tube: https://buildyourcnc.com/item/pneumatic-hydraulic-Tube-Fitting-Barbed-to-Male