We swapped out the old bearings on our moulder spindle and the outboard, pully end is running too hot. Causes? Cleaned everything, warmed bearings to install, chilled shaft to slip on bearings. Too tight?
6000 rpm 3 bearing spindle.

Are the bearings permanently lubed or are there grease fittings. If the latter you may have too much grease. Greasing until you see squeeze out is not good. The grease should be one third of full load.
Otherwise, were the races fully seated, I'm sure you swapped for the same spec bearings but some types of seals don't tolerate high spindle speeds. Too much preload if there is a preload nut?

Good point. Previous bearings were open, new ones were sealed, rz seals. The other 2 verical spindles run normal temp.
Shoot, maybe i have to take it apart again. Maybe too much preload. The manual is useless, cant even see the parts in it.

Belt tension too high?

No, i loosened and tightened belts and ran both ways. Same deal. Pulleys inline as well. Called local machine shop and he thinks preloading is too tight as well. Time to take it all out...again.

How warm did you get the bearings when you installed them? Enough to soften and cause the grease to run to one side? Cook the seals? Personally I would never heat sealed bearings.

Not that hot Rich, maybe 80c. Chilled the shaft outside to 0c. once at room temp you cannot slide the bearings onto the shaft, by doing this method they simply slide on perfectly.
We use a hot air gun to warm the bearing race.

I bought a brand new M-J dip bed gang rip with a monstrous 3 ph direct drive motor. It sat for a couple of months before the space was ready, but we had our best electrician on it. Started it up, and with 20 minutes, it started screaming. A motor bearing was over 600 degrees! Called the factory, they overnighted a new pair, gratis. Their explanation was that it was not unusual on high load, high speed spindles to cook a bearing every now and then. The new ones were fine, and the saw still runs great.

Hi Dave,
I the classes I took like 20 years ago we got told not to use sealed Bearings on Moulder Spindle's I did use some sealed once on our old Watkin as nothing else was available on short notice. I did not do this without calling one of the Instructors that explained to us on how to rebuild spindles. He recommended we should only start the spindle for a few sort bursts , so the grease had a chance to solely heat up and get a chance to spread out evenly in the bearings. Same instructor told us on open angular precision contact bearings after cleaning ( or installing new Bearings)we should only apply the grease ( Kluber) to the outsides of the bearings and the let the heat make the grease work itself in the bearings. Same thing again start them up in short bursts and give this some time.
I should also mention some of these bearings an molder spindles have
direction they need to be slipped on the spindle with the correct side facing each other.
Please understand I am a woodworker not a professional molder operator.
Just passing on things I learned from others. And had to do myself occasionally.

Thanks Fred. From your explanation i probably did not do any of those things correctly, hah, so its not surprising i am having issues. I better read the timken manual as well. Stupid me.
Much appreciate the knowledge and input!

On my Martin four sider planer moulder they instruct along the same lines Fred mentioned.
After greasing run for 1 minute - shut down for 1 minute- run 5 minutes - shut down 5 minutes - run 10 minutes and then shut down 10 minutes before running any material.

I had a look at RZ bearings and the seals are non contact on the inner race so they will be fine for the spindle. I doubt you have angular contact bearings which are hella expensive and have very tight tolerances for preload, Usually the spindle will have spacers that are designed to give precise preload when the nut is torqued.
I'm assuming you have redone the preload so this is just to say that your bearing shouldn't cause any issues due to the seals

It's possible that the bearings were put in too tightly or that the shaft wasn't greased well enough. It could also be because the spindle isn't getting enough air to cool it down. Check the fitting and lubrication, and think about adding a fan or a water-cooling system to help cool it down even more.