After running my NM200 at about 3100 RPM for one hour or so under light load, my infrared temp probe reads about 140 Degrees F or so. After about 2 hours, it gets to be about 155 or so. I shut it down when it hits 160 because I get nervous. The location where the highest temp is found is on milling head (have to take off the shroud), closest to the arbor.

I had one bearing already go out in the spindle, which I have since replaced. The first bearing was contaminated with metal shavings and fibers. I believe the contamination was most likely present at the factory when it was assembled. It also had almost no lubrication, but it's possible that the lube burned off under the high temp of the failing bearing.

SO it's the chicken and the egg dilema. Did the heat burn off the lube and cause the failure which caused the metal shavings?
OR
Was the metal contamination the initial culpret causing wear, heat, etc...

To make a long story short, I wanted to know what normal operating temperature is for a spindle (and bearings)? My new bearings are in place (replaced them all) and I am reading similar temps.

Thoughts anyone?

After running my NM200 at about 3100 RPM for one hour or so under light load, my infrared temp probe reads about 140 Degrees F or so. After about 2 hours, it gets to be about 155 or so. I shut it down when it hits 160 because I get nervous. The location where the highest temp is found is on milling head (have to take off the shroud), closest to the arbor.

I had one bearing already go out in the spindle, which I have since replaced. The first bearing was contaminated with metal shavings and fibers. I believe the contamination was most likely present at the factory when it was assembled. It also had almost no lubrication, but it's possible that the lube burned off under the high temp of the failing bearing.

SO it's the chicken and the egg dilema. Did the heat burn off the lube and cause the failure which caused the metal shavings?
OR
Was the metal contamination the initial culpret causing wear, heat, etc...

To make a long story short, I wanted to know what normal operating temperature is for a spindle (and bearings)? My new bearings are in place (replaced them all) and I am reading similar temps.

Thoughts anyone?

spindles get hot normally, but im not sure if 160 is normal. my nm070 spindle after an hour is hot to the touch, but not so much i cant keep my hand on it. a guess would be 140-160f.

part of this heat comes from the tool friction, part from bearing friction. i dont have any strong airflow in my enclosure though, so it could probably be alot cooler.

i dont think 160f is hot enough to harm the grease in the spindle bearings, but you should lube it regularly anyway methinks.

Chris,
I emailed Khai about this and this is what he told me

"There were the odd NM-200 machine that ran hotter than normal. We have since changed our procedure, running the machine for a few hours, making sure the temp is within normal spec which is around 65 degrees Celsius before it is shipped."

Which if I am correct 65 c is 150 degree F. So thats right in the range I would say. Give or take. And is the infrared one of the HF ones ? If so the temp reading could be off on the unit. I ll be interested to see how the fan setup you mentioned turns out.

Thanks for the info. My calc says 65C is 149F. I haven't had to run it for very long since I installed the cooling fans, so not long enough to test the temperature. Should have some heavier work coming up soon. I'll post the results of the cooling fan mods. The little 3" computer fans really move quite a bit of air. I want to install some splash guards too. When I have more results, I'll post the whole setup.

I'm not sure about the infrared temp probe. It was a $20 special at Harbor Freight. Seemed to be fairly accurate in some quick comparison tests with my regular thermometer, but I know that reflective surfaces DO screw up the reading.... Works best on dull flat surfaces.

I finally got around to checking the spindle temp on my Grizzly G3616 and found it also got quite warm at higher RPM. I was running it at 2900 RPM for about 30 minutes. The temp probe read 130 degrees F. That is about on par for the Novakon spindle after that amount of time. Did not have a reason to run the Grizzly mill for longer, not sure what the max temp would have been.

Running the Grizzly at 1000 RPM for about two hours only generated about 120 degrees F, but I don't have temps for the Novakon spindle under similar conditions. I think the Novakon spindle is maintaining a reasonable temp at high speeds, but as I have stated in other posts, I have not been able to run the spindle at the 4000 RPM stated in the specifications. The max speed appears to be about 3120. I could mess with the VFD, but I'm sure that would generate even more heat and send it into a dangerous temp range. Plus my motor does not have a max RPM rating and I don't want to toast it.

When new, my NM135 spindle would run "unbelieveably hot" (can't touch it), but after a dozen or two hours of operation or so, now only runs "hot" ("hot" = can only touch for a couple of seconds).

I don't have an IR tempprobe, but I do have a 120VAC Wattmeter, which gives an idea of the spindle power dissipation, which is directly related to temperature. The power drops substantially as the spindle warms up:

Mill idle: 57 Watts
@6krpm from cold, no load: @time=10seconds: 1000W
time=1m: 800W
time=4m: 660W
time=10m: 550W
time=15m: 530W

When the spindle was new, the time=15m would've been well over 700W - maybe 800. So my spindle seemed to get better with age. And the TIR still looks OK.