Plumbing a water-cooled spindle.

[Kitwn]

Well it used to be green! That's only the fluorescein dye anyway. I Think the last time I actually bought anti-freeze in a shop Mrs Thatcher was still PM. I'd had enough of grovelling about under cars at the side of the road by then and vowed that as soon as I could afford it I was going to pay someone else to service my car. I would, of course, now purchase the latest safety approved product from a reputable Australian supplier.

Kit

[magicniner]

Any good quality Ethylene Glycol based anti-freeze has corrosion inhibitors which will work well in a system which includes Iron, Steel, Aluminium, and/or Brass, use De-Ionised water too to avoid any chance of impurities building up inside the spindle.

[Kitwn]

I'm afraid Ethylene Glycol is out due the risk of poisoning the dogs if I get a leak and they lick it up. I'm tempted but my wife would never forgive me! The Proylene Glycol version is OK so I'm going to head for our local Auto-Pro and read the labels very carefully.

I obviously don't need the anti-freeze/anti-boiling properties of the stuff but some corosion inhibiters might be nice. I am also concerned about algae growing in the water. It doesn't get hot enough to kill the stuff but the ambient temperture here is perfect for it. If I don't find a suitable anti-freeze I might just go for adding a little chlorine based bleach (NOT the 'oxygen' stuff). A little further reading on Wikipedia sugests that a weak solution of 200ppm Sodium Hypochlorite will be strong enough for bug killing but won't attack the metals. Standard household bleach is about 5% (50,000ppm) so a couple of tablespoons of bleach in 10l of distilled water should do the trick.

Thanks for all the comments from everyone so far, this has prompted some interesting reading.

Kit

[Voicecoil]

You should be aware that Sodium Hypochlorite is somewhat alkaline in solution and hence will attack aluminium a bit. Should be OK on plastics and stainless steel though. Alternatively once the bleach is dissolved you could add a little acid to compensate - you should then have an essentially neutral solution containing some chlorine - how soon this would diffuse out through the piping though I don't know.

[cropwell]

If all you are looking at is corrosion inhibition, how about something like Fernox - used in central heating. I haven't researched it, this is just tossing an idea into the pot.

[RobC]

I used a pond pump too but found it rather noisy and with it being directly mains powered couldn't easily control it from my panel. I then went to a 24v self priming pump and that way I just control it via a normal toggle switch when required as the temperature reaches a certain temp.

[cropwell]

When I get round to my build, I have acquired a second hand 24v pump, fan and radiator (120mm) and a perspex header tank, so I plan to mount it all directly on the machine. I have some NC 40degC thermal switches, so one of those will go on the spindle.

[magicniner]

If all you are looking at is corrosion inhibition, how about something like Fernox - used in central heating. I haven't researched it, this is just tossing an idea into the pot.

An excellent suggestion, used with DI water that should cover all the bases, don't use bleach, if you need an anti-biological it needs to be PH neutral, but you could run your coolant through a pond/aquarium UV unit on it's return to the tank to keep the biological load to a minimum or you could have a submersible UV unit in the tank.

[Kitwn]

Some good ideas there, thanks everyone. Re using bleach: the body of the spindle is aluminium so there is a risk there, though Wikipedia says it'a not corrosive at 200ppm hence the limit of concentration there. At the moment I'm still using plain old distilled water with no signs of an ominous green tinge.

Re the use of switches, thermostats etc for turning pumps on and of: my 240v pond pump is quieter than the VFD fan so I simply have it on the same mains supply switch. If the VFD is on, the pump is on. After a long cut yesterday for levelling the machine bed I found the tool and spindle shaft quite warm. I turned the pump off and the lower body of the spindle warmed up noticably so I turned the pump back on and it cooled almost immediately. This makes me more certain (as I said in the other recent thread about switching pumps on and off) that leaving the cooling on continuously during a working session will help cool the spindle faster after one cut and so reduce the starting temperature for the next. And it's simpler to implement. KISS!

Kit

[cropwell]

Again, an off the wall suggestion, to inhibit algal growth how about a phenol based disinfectant, like Jeyes Fluid ? I do not know the pH properties of it though. You certainly would not need much.