Mill Spindle Overheating (Rockwell 21-100)

[alcro1998]

So I have recently acquired a Rockwell 21-100 milling machine. I originally purchased the machine to use the head since the seller told me the machine was missing the table but turned out everything was there. The machine looks nice and is smooth with little wear.

As the title states, the spindle gets very very hot when at the higher speeds. I ran the machine for a little bit to test it out and immediately noticed that it was toasty. Toasty enough to think that the spindle would weld itself together if left alone for too long. It is fine in the 370-1170rpm 3 slow speeds since it is slow but when at the 2440-6300rpm range it gets hot fast. Like a few seconds fast at the highest rpm.

Obviously? this is a spindle bearing issue but the spindle runout on the r8 taper is .0003-.0004 and the face of the spindle is about .0005. This runout seems pretty good to me. I feel like if the bearings were trashed then the runout would be worse. There also seems to be a little noise coming from the spindle and the noise lessens when the quill is all the way down.

I am wondering if anyone has encountered this issue with this machine and what the cause could be. I have not pulled the spindle yet.

My guesses are that -

1. Bearings are shot - Maybe just 1 since the runout is good? Maybe just the bearing at the top of the spindle is bad and this causes the noise change and heat? Dunno

2. The grease in the bearings has dried up - I think this mill sat a bit after the shop closed that it was in.

3. The bearings are too tight in the spindle - Not sure if this is possible but maybe someone has been in the spindle and forgot a shim or something.

Any suggestions are greatly appreciated! Thank you!

 

[wood2steel]

Your heat build up is definitely be a lack of lubrication issue. You will need to get inside that spindle cartridge before you run it anymore. There could be as many as 5 bearings supporting that design . Some allowed for gravity oil to get to the bearings but on many of those their would have been a Kluber type grease packed and sealed in place so no further lube could get to bearings. PM if you need to talk through some scenarios that you could face with service. Good luck
Johnny

 

[alcro1998]

Your heat build up is definitely be a lack of lubrication issue. You will need to get inside that spindle cartridge before you run it anymore. There could be as many as 5 bearings supporting that design . Some allowed for gravity oil to get to the bearings but on many of those their would have been a Kluber type grease packed and sealed in place so no further lube could get to bearings. PM if you need to talk through some scenarios that you could face with service. Good luck
Johnny

Thanks for the reply. My best guess was lack of lubrication because I guess even bad bearings shouldn't run this hot if they are lubricated. I think that these bearings are sealed in place. I will take the spindle apart tomorrow and see what is up. For sure won't be running it anymore.

 

[wood2steel]

I am actually facing a similar situation on on an Adcock shipley horizontal mill. The machine came with zerk fittings to lube the spindle but there's no concrete info out there regarding oil or grease usage and nobody has a clue what has even been used in recent years. Would hate to torch those bearings on a gamble. I have to believe the era those machines were built in; it was a common practice to service those type spindle cartridges periodically. Also had a Burke Millrite some 20 years ago that had to be pulled out for your same concerns. Keep me posted how things turn out!

 

[ps123]

The original spindle bearings on these were deep groove ball bearings with inner races ground to provide some preload. You should consider upgrading to angular contact bearings. See my notes on my rebuild:

Rockwell 21-100 Spindle Rebuild

Re-posting after server crash issue... I recently acquired one of these vertical mills, and will be rebuilding and refinishing it as time permits. Most of it is still in pieces, but I managed to just complete the spindle rebuild. I leveraged some ideas posted on the Yahoo Rockwell Milling...

www.hobby-machinist.com

 

[eKretz]

You should probably measure the temperature and get a quantitative idea of how hot they're actually getting. I just recently replaced the angular contact spindle bearings in my Wells Index 847 and did the new bearing run-in procedure. At the end of the job, the temp stabilized at 116° F at 4,200 RPM. The bearings are grease lubricated. Ball bearings should not generally be run at any hotter than 130°ish absolute max in a machine tool.

 

[mottrhed]

Excessive heat can be caused by many things in a spindle. A few off the to off my head

Lack of preload -worn bearings or something loosened up
Excessive preload - something overtightened or shifted
Lack of lubrication
Excessive lubrication
Misalignments
Belt slip (if belt driven)
Motor heat due to excessive load (if motorized)

If the history is unknown all bets are off-maybe the wrong bearing are installed.. who knows.

There also could be a contact seal that is generating the heat.

Disassembly is in order to get to the bottom of it.

Let me know if you run into any questions or challenges along the way.

 

[alcro1998]

I might consider the angular contact bearings and I saw your thread on the bearing replacement before posting here.

The spindle gets hot fast! I can’t find my thermometer but I’m scared to run it too long and this is not a common thing with this mill.

I pulled the quill today and there’s a noticeable crunch when turning the spindle very slow so that’s not good.

I’ll update everyone more when the spindle is out.

Thanks for all the replys!

 

[eKretz]

Yeah, crunchy is not a good symptom. Definitely time to strip her down.

 

[alcro1998]

Yeah, crunchy is not a good symptom. Definitely time to strip her down.

Spindle is out and more crunchy feeling than ever. Looks like oil may have leaked into the spindle and washed the grease out.

I’m looking at possibly installing NSK matched angular contact bearings.