Spindle, how hot?

Hey all, wondering if anyone has an idea as to what temperature a spindle should be operating at, and when is too hot/warm?

I am using a 2.2kw HY water-cooled spindle. It has about 10ft of tube x2 for feed and return. It runs to a sealed 5gal bucket, filled with a gallon of 50/50 antifreeze, and an additional gallon of distilled water. The line is somewhat restricted because I put a flow indicator at the top of the spindle, which has a smaller ID than the tubing. It was unavoidable, I like knowing my pump is working seen as I kept the cheap pump that came with the HY spindle kit. As far as the pump goes, once I realized it was 220V LOL its been humming along just fine. Maybe put a fan in the lid of the bucket?

Anyways. For those of you with spindles how hot do they get? Mine wasn’t too hot to touch, it was just hotter than I was used to. I’ll have to remember to get a reading next time.

I had been doing shorter, <30min jobs. Recently I did a longer 4.5-5 hour job plus a couple of breaks to change tools and re-Z. It was a tile job, so 3 tools x3 tiles =9 quick breaks.(it turned out pretty decent 72"x8" sign on the woodworker.)

Hey Tim,

I have a german 2.2 kW water-cooled 24,000 rpm spindle. In the spindle manual it says the coolant temperature must not exceed 40 °C at the output of spindle.

On a related note, my manufacturer recommends a flow rate of 0.5L/Kw/min and not less than 1.5L/min.

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Hey Tom,

on mine it says not below 1 L/min

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Hey Tim,

I think you should always monitor temperature. I know there exist thermometers for the tube for this. Or, if you can afford it, use a spindle cooling station that monitors flow rate and overtemperature (example, specs) and that is able to stop the spindle via the VFD in case the values reach the limits.

Note: Recategorizing to from “Onefinity CNC Machines > Upgrades” to “Spindle/VFD (Aftermarket)”

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I ran my spindle for like 3.5 hours straight this weekend. Water temps started at 27.6 and got up to 30.4 and stabilized. Running at 14000RPM for most of the cut… Spindle was warm to the touch… It was 28-29 C in my garage in Texas at the time.

Thanks for the info. I have always intended to upgrade my cooling, not really been comfortable with the bucket. I’ll have to run it for a while later today and get some temp readings, as well as flow rate.

@Dustoff00 My water temps definitely rose more than 3ish degrees, running mostly at 18k.

I am running a VEVOR Water Chiller CW-3000 that was procured from amazon. It is not a true professional chiller, but pulls air across the cheap radiator looking device to help dissipate heat. I know many just use the bucket and pump and are fine, but I had to swap to a 110volt pump and this has a flow alarm and temp alarm if the water gets too hot or the pump stops flowing, so I got several benefits from the one device, vs. having to buy a bunch of individual parts along with the new pump.


I have my MY 2.2kw spindle being fed from a bucket with plain water in it. There’s about 2 gallons in it and maybe another in the line. I’ve run for hours and the spindle has gotten warm to the touch but no where near the point where I couldn’t leave my hand on it comfortably. I checked the temp once and it was around 75f.

The flow with the supplied pump was too low IMO and was a very cheap Chinese pump. So I replaced it with a better US made pump. I have a flow meter on it with an alarm set at .1g/m. It runs at about .21g/m. The bottleneck is the fittings on the spindle. If I bypass the spindle I get over .5g/m. I could upgrade to a higher pressure pump or a chiller but I don’t see the need. II have numerous tools like drills and sanders that get much hotter that don’t have issues.

But heat is a function of work. If you push the spindle to it’s limits it’s going to heat up. The only things that I use that will push it are raised panel bits and a 2 3/8" surfacing bit. But those only run for a short period of time. The bits I use that run for hours are things like 1/4" endmill.

My advice is to stick with a bucket and and keep an eye on the temperature. If it gets more than just normal warm then look to add some sort of cooling. A chiller would work but my plan was to add a simple transmission radiator and fan. I like to keep things simple if possible.

i bought a fish tank temp gauge a couple of months ago and it works great as a visual guide incase the temp starts creeping up


Well I ran it for 1.5 hours with no load, just spinning in the air at 18k with a bit in it. It got to around 100°-110°F(38°-43°C). Pump Is only putting out about .2g/m (800ml). I’ll try upgrading the pump, but I wonder if that will improve the temp; the water is consistently around 5°F less than the exterior of the spindle. Will increasing flow improve temp if the spindle and water temp rise evenly together? I should mention I was checking temp with a probably not very accurate contactless temperature probe.

I’m going to do some experimenting hopefully this week, maybe check out that

and see what I come up with.