Plumbing a water-cooled spindle.

[Kitwn]

For my new 2.2kW water-cooled spindle I bought a pond pump and 10 metres of 5mm i/d PVC pipe from my local Home Hardware. A quick test gave a flow rate (with no head) of only 30 l/hour. Another test with only 250mm of the pipe gave 4 times that rate. This showed that it's the length of pipe that reduces the rate, not just the fact of choking the pump outlet to 5mm. A return trip to Home Hardware found that the 8mm size pipe will just accept the 5mm size inside it so I bought 10 metres of that. This size will also just fit into my new 70x15mm Banggood drag chains. A bit of PVC pipe glue plus some heat-shrink sleeving for good measure created a couple of stubs of 5mm pipe to connect to the spindle. The overall flow rate through the spindle is now 60l/hour.
Another advantage for anyone else who follows this plan is that the pump I bought came with a plastic outlet barb the right size for the 8mm pipe whereas I'd had to find a brass fitting and modify it in my lathe for the 5mm size.

Kit

PS What do you use to prevent corrosion and algal growth in your cooling water? I'm using distilled water and wanted to add some car anti-freeze (ha-ha, the lowest temperature ever recorded where I live is 7.6C) but was advised not to as we didn't know exactly what metals were in the spindle and it might have an adverse reaction.