K&T vertical mill, spindle runs hot

[projectnut]

160 F is a typical operating temperature for rolling element bearings, it is 60 Deg. higher then human body temps. SKF gives some guidance here.
http://evolution.skf.com/us/whats-normalthe-role-of-temperature-in-bearing-applications-3/

While it may be wise to inspect the bearings to be sure they are properly lubricated I do agree that bearings of that era do run HOT to the touch. Here's a warning note from the operators manual concerning the heat generated by the motor bearings in my Sanford MG surface grinder:

 

[Bob Korves]

160 F is a typical operating temperature for rolling element bearings, it is 60 Deg. higher then human body temps. SKF gives some guidance here.
http://evolution.skf.com/us/whats-normalthe-role-of-temperature-in-bearing-applications-3/

Agreed that 160 F. is a normal temperature for bearing elements. However, the OP was not likely measuring the actual bearing elements' temperature, he was likely measuring the hefty cast iron housing they are mounted in, which will be at a much lower temperature than the bearings themselves are. Carbon steels typically start to lose their hardness above about 400 F., alloy steels somewhat higher depending on the alloy, so by the time the housing gets to 160 F., the bearings themselves may already be ruined. It is certainly worth a look if the OP was not measuring the temp. of the bearings themselves. The mill was also only doing light work for 30 minutes, which usually should not show that much bearing heat, though I must admit to not knowing specifically about K&T vertical mill operating instructions and limitations, and do not even know the exact model, the OP never told us...

 

[Janderso]

Or perhaps petrified grease in the bearings after decades without being serviced...

Watching H&W machine’s video on spindle bearing replacement/packing, the tech., Used a very small amount of grease. He said, too much grease will cause overheating.
Just my 2 cents.
I have run my Bridgeport enough to verify it runs very cool at the spindle.
Something is going on with your mill. Imho

 

[P. Waller]

Agreed that 160 F. is a normal temperature for bearing elements. However, the OP was not likely measuring the actual bearing elements' temperature, he was likely measuring the hefty cast iron housing they are mounted in, which will be at a much lower temperature than the bearings themselves are. Carbon steels typically start to lose their hardness above about 400 F., alloy steels somewhat higher depending on the alloy, so by the time the housing gets to 160 F., the bearings themselves may already be ruined. It is certainly worth a look if the OP was not measuring the temp. of the bearings themselves. The mill was also only doing light work for 30 minutes, which usually should not show that much bearing heat, though I must admit to not knowing specifically about K&T vertical mill operating instructions and limitations, and do not even know the exact model, the OP never told us...

Any temperature above 169.3216 Deg. F is out of spec, this is why most machines are supplied with spindle bearing temperature monitoring equipment.
Your machines do not have this feature? Shame shame, you probably use them up to 170.0000 Deg. F. A prolonged period of more then 171.0032 Deg. F will result in catastrophic failure.

 

[amesgang]

I changed the oil, backed off the pre load on the bearings, was set very tight. retested, still gets hot on high speed (1000 rpm), does not heat up on low speed. K&T 2H vertical mill.