View Full Version : Internal Spindle Coolant Fluid

11-29-2011, 05:26 PM
I've got a liquid cooled spindle, and I've used distilled water and white vinegar trying to keep it from creating mold. However it's starting to grow a white or very pale looking algee. I've thought about adding maybe bleach, chlorine, or alcohol to the mix, but I'm afraid of what it may do tot he submersable pump and tubes, as well as the interior of the spindle...

Any thoughts form someone that may know of a good solution? What is everyone else using for their cooling fluid? This is a closed circuit. It's not a cutting fluid. Only a cooling fluid for the spindle of my cnc router.

Thanks for any input you can share.


11-29-2011, 06:00 PM
I just use radiator coolant , my clear tube will slightly discolor to white after 6 months.

Cheers. Michael

11-29-2011, 08:53 PM
We use dowtherm or dowfrost in all our water cooled spindles.

11-29-2011, 10:19 PM
I just looked into the Dowtherm and Dowfrost products. The information they have on all the tech sheets is great, but they don't say what the concentration is being mixed with. I assume it's water...? I also looked into where it may be sold, but am not finding much info on re-sellers. Where do you buy your Dow products from?

11-29-2011, 10:31 PM
Wow, I just looked further into that stuff, and it's pretty toxic. There are lots of warning about it's handling and disposing of. I was hoping to find something a little more bio friendly. And a bit less expensive too. It looks to be about 80 bucks for a gallon. Unless that would last me a few years. I don't want to flush so much chemical so often, producing something not easily disposed of...

11-29-2011, 11:52 PM
We mix at anywhere from 15 to 20 percent with water. When mixed correctly, we probably run it 5 years before changing. Even std antifreeze has all those warnings. Hell, even wd 40 does! The stuff does stay very stable with no growth, and I see it in plastic, brass, and stainless lines without issues. Most of the builders of our precision machines require one or the other. The other cooled spindles are generally velocite 6 light oil.

11-30-2011, 12:16 AM
Adding a small amount of iodine to water will quite effectively keep it from growing anything.

11-30-2011, 12:21 AM
Have you tried to buy iodine lately?

11-30-2011, 12:26 AM
Those restrictions are, I believe, in relation to crystal iodine. You should still be able to buy liquid iodine at your local drug store. Also, I'm in Canada so we don't have that crazy rule here :)

The linked restriction is terribly pointless as you can easily make crystal iodine. Make magazine did a video at Weekend Project: How to Make Iodine - YouTube covering the conversion.

Again though you just need the easy to get liquid version to keep water from going funky.

11-30-2011, 12:47 AM
That's the problem, even the guy that makes the liquid iodine for campers just got shut down. Damn meth heads!

11-30-2011, 01:00 AM
5 years? at only 20% of 3 gallons, that's not bad. I don't see a lot of retailers though. Do you buy it directly from Dow?

11-30-2011, 01:26 PM
I called Dow today. They were not interested in making suggestions. Seems like the chemicals they sell are so costic that they don't' mix well with lots of materials... The girl I spoke with refused to make any suggestions without knowing the precise 100% breakdown of materials in the circuit of tubes and pumps used in my system.

I was able to find the manufacturer's number for the submersible pump though. When I called them to ask about what kinds of chemicals are safe to run through their pump. He explained I could run the following Alcohols without harming the internal seals or parts that make up the pump works.


However others would slowly degrade parts and seals... The Tech at Frankllin suggested about a 20% mix to keep things from growing in the water. I'm using a Franklin Electric- Lil' Giant Pump.

12-15-2011, 07:56 PM
I am From Texas and there is too much Calcium in our water and I am thinking of using Prestone 50/50 mix. It good in my truck. What do you think of this?

12-15-2011, 10:28 PM
I am From Texas and there is too much Calcium in our water and I am thinking of using Prestone 50/50 mix. It good in my truck. What do you think of this?

I think its smart.


03-22-2014, 09:01 PM
I have a chinese 4.5kw water cooled spindle and I have used water from day one. In short, I always hated using just water but I could never get a straight answer on what was best to use. I have researched many threads in this forum and there are 100 different solutions. Here is what I'm looking for in a coolant:

- Non corrosive (#1 because I think there has been corrosion using water)
- Non conductive (if it does spill onto my spindle, I would prefer it not to short out)
- prevents alge growth (this was an issue too using just water)
- low viscosity (my pump is small, 50W fish tank pump (http://www.amazon.com/gp/product/B002JPIQ1Y/) but works very well)
- inexpensive

So, with this in mind, I found this product PrimoChill Pure Performance (http://www.amazon.com/PrimoChill-Performance-WaterCooling-Coolant--Clear/dp/B000XJOJC8/). Free shipping with Amazon Prime so total cost is about $48/gallon.

And I'm going to use this container Rubbermaid 7J72 14-cup (http://www.amazon.com/Rubbermaid-7J72-Square-Storage-Container/dp/B000WEMFOS/) which will just fit my pump and holds a little under a gallon of fluid.

This leads into another question I have which is how much cooling fluid should I use if I don't have it running through a radiator? How hot can the fluid get before I should be concerned. FYI, I cut 1/2in plywood with a 5/32 endmill that I think barely loads my 4.5kw spindle (12,000 rpm at 140ipm). In addition, the housing on the spindle is massive and the aluminum mount is massive so plenty of thermal mass for the heat to soak into. I have ran the cnc with no fluid running through it many times (because a fitting got clogged with alge and rust) and the motor is only slightly warm (maybe 110°F at most). I think the only concern would be the bearings getting too hot and shortening the life on them.

I will post again once I have this all setup.