Water Cooled CNC Router Spindle

Hi everyone! We’ve been putting our OmioCNC x8 to good use this season and wanted to share a water cooling solution for our 2.2kW router spindle that doesn’t involve a bucket of dirty water. During some of our off-season testing, we discovered that the bucket of water quickly became “heat soaked,” causing the spindle to heat up significantly during long jobs. I picked up some PC water cooling hardware for cheap online and put together a simple cooling loop that lives on the CNC gantry. The entire system is self-contained, so there’s no need for a bucket or AC pump. Even after long jobs at max RPM, the spindle is kept warm to the touch.

Below is a list of all the components I used to set up the cooling system, minus some electrical connectors and a DC power supply to run the fans and pump. This list is by no means perfect. Other than the radiator, most of the list can be substituted for comparable components. I chose this radiator specifically because it has the reservoir built in, eliminating the overhead of adding another element to the loop. Note that air is blowing through the radiator toward the gantry. We chose this airflow direction since it forces all swarf that would’ve otherwise been stuck on the back side of the radiator (if the airflow was reversed) to pass through the filter. This airflow direction also has the side-effect of keeping swarf away from the space between the gantry and the radiator.

  • Metric M8 M8X1 Male to Barb Hose ID 1/4” 6mm Brass (Qty 2) (link)
  • 120mm Fan Filters (link)
  • Mayhems XT-1 Nuke Clear Concentrate Coolant 100ml - This was the coolant with the longest “lifetime” I could find. Any coolant will likely work, honestly. (link)
  • Tygon 2475 Ultra Chemical Resistant Plasticizer Free Tubing - 1/4" ID (3/8" OD) (12ft) (link)
  • Swiftech MCR220 “Quiet Power” 2 x 120mm Radiator w/ Reservoir (link)
  • Phobya DC12-260 PWM 12V Water Cooling Pump (link)
  • Koolance G1/4 Thread 1/4" x 3/8" (6mm x 10mm) Compression Fitting (Qty 2) (link)
  • Koolance 1/4" (6mm) ID G1/4 Threaded Angled Nozzles Pair (Qty 2) (link)
  • Scythe Ultra Kaze 120mm x 38mm Fan - 3,000RPM (Qty 2) (link)

Total cost was about $200 shipped. The price may seem kind of high for a something that already works “good enough,” but we feel the cost outweighs the benefits. We no longer have to empty the bucket of nasty water every week, clean the water cooling loop that runs through the spindle, worry about mold, algae, or rust, or risk overheating the spindle. The coolant is designed to kill bacteria, mold, etc. that may begin to flourish in the lines and keep rust from forming inside of the spindle, so now if I want to cut something, I just turn on the DC supply and start cutting. No mess, no fuss.

Hope this helps!

Here are a few more pictures of our setup (also, don’t hate on my zip tie hose clamps, they work well enough):


Awesome thanks for sharing! I’m currently building up a CNC router using a similar 2.2kW spindle and I’m working on the cooling loop, so this is great info.

What size bucket were you using as the reservoir before? A normal 5 gallon one? I’m surprised that got heat soaked so soon. I suppose if it was a sealed plastic container it makes sense that it wasn’t being cooled by ambient air fast enough though.

You mentioned that the bucket of water was dirty. Was this picking up particulate from within the spindle, or was debris from the cutting job getting into the bucket? Did you have any additives in the bucket?

lastly, how are you liking that Omio? Has Y axis flex in the gantry posed an issue at all? I know on some of the cheaper Omio clones, you can press on the spindle in the Y direction and see noticeable flex in the gantry, because the X liner rails weren’t supported along the full length. Is this an issue at all on the Omio as well?

Thanks again

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Thank you for this awesome information! We’re looking at upgrading our spindle after this year and I will certainly come back to reference this!

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No problem! I’m glad people are finding it useful. We were using a standard (5-gallon) bucket.

Because of its location, the bucket did have a lid on it. Before putting the PC radiator system on our CNC, the water temperature reached ~100F during a 4-hour cut. I’m not sure whether those temperatures were anything to be concerned about, but I’d rather err on the side of caution.

If the bucket wasn’t changed out weekly, mold and algae would start to form. While this shouldn’t be a problem in the near-term, during periods of little use (during the summer), the bucket and pump would need a deep cleaning before operating. Our build space is not temperature controlled, so the wide temperature and humidity swings probably contributed to the problem. The pump that shipped with the Omio was also of poor quality and liked to retain mold/algae, so instead of replacing it, I decided to fix it permanently.

The Omio has treated us well so far. The X and Y axes are on heavy duty rails pushed along by large lead screws, so backlash hasn’t been a problem. I can’t speak to the smaller x4 or x6 versions, but the x8 is built like a tank.

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How loud would you estimate this setup is?

About as loud as a gaming PC. It’s definitely quieter than the spindle cutting through aluminum!

Has the added weight to the gantry caused any issues with gantry deflection?

Use the smart relay on your vfd to turn on the pump (pass the dc negative to the pump and run positive to pump from ps), and set a dwell in your post to allow for the pump to start and for the spindle to come up to full speed. You can set a delay on the relay/pump to to stay running for a period of time between cuts so you dont have it starting and stopping on short durations between jobs. Also they make in-line flow indicators to make it easier to see the coolant pumping too. I’ve been doing this since about 2010. Its great. McMaster Carr also has self sealing fittings so you can disconnect the setup too and not make a mess.

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The CNC doesn’t even know the extra ~2lbs are even there.

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I hadn’t looked into automating the power on/off process, but thanks for the tip! I’m reluctant to mess with anything during build season, but I’ll add it to my list of to-do’s for May!

is the added complexity worth it over just making some heatsinks? i think our spindle is in the same area, but even cutting at high rpms i doubt im approaching the the power limits of the spindle, it gets hot, but not too hot to touch. the limiting factor in our situation is that i think the machine just isnt rigid enough to put more load on the spindle. i think the highest load i’ve run are my 60% stepover adaptive paths in 1/8th aluminum with a 3/16 cutter. i think i was at 24500rpm and just over 100ipm. sure the rpms are still up during finishing, but the the load is really light on the cutter, usually .010 stepover on a slower feed. i have more concern with the heat in the stepper motors than the spindle.