Warm bearing

[cdhknives]

A couple of days ago I ran my Atlas for an hour or so at 685 RPM spindle speed while taking light cuts for the tailstock alignment bar. Since this lathe was stored for several decades without lube and periodic rotation, bearing damage has been something I have been watching for closely. This was the first time I had run at this speed (or higher) for more than a few seconds 'just to see what it did'.

I felt around during operation and after shutting down and the right spindle bearing was slightly warm. Not enough to be alarming, but there was a difference between the left and right, and that was unusual in and of itself.

I have noticeable oil draining from the seam where the bearing seats into the face of the headstock, so they are getting oil.

At what point do I need to get concerned and look hard at replacement bearings (yes it is a Timken bearing unit) as a preventive measure against spindle damage from an overheating bearing?

 

[iron man]

I wish there was a hard and fast rule to this mine has done what yours is doing for the past 15 years and it is still fine as long as I keep it lubed up. I quite using oil in the cups and used straight STP it sticks and stays better. Ray

 

[Ray C]

It's pretty unlikely you'll get spindle damage due to worn bearings. The bearing itself will get beat up but, for damage to happen to the spindle, that will take some extreme abuse for that to happen.

When you start noticing heat issues, you should be able to measure accuracy problems by reading directly off a smooth part of the spindle nose. If you tug on the spindle in different ways, you'll get quite a bit of deflection (as in >= 0.001").

BTW: I had a TH-42 which was a Timken bearing Atlas...


Ray

I wish there was a hard and fast rule to this mine has done what yours is doing for the past 15 years and it is still fine as long as I keep it lubed up. I quite using oil in the cups and used straight STP it sticks and stays better. Ray

 

[itsme_Bernie]

Bearings getting warm is totally normal, and many times preferred. Depending on the operation, one might prefer warm bearings before working!

I am sure you have enough oil, observing it coming from your bearings now- how does it sound? How does the spindle feel when you turn it with your hand?
What oil are you using now?
Before you would need to consider new bearings at all, there are instructions posted (someplace, or I have them at home) on checking and adjusting the spindle bearing "preload"- since the bearings are tapered.

 

[cdhknives]

There is zero grittiness or similar when turning the spindle by hand.

The idler bearings are too noisy for me to really hear significant noise form the spindle bearings.

I'm using non-detergent SAE 20W motor oil for lube, and I pour it in as it pours out.

There is a few seconds of run down with the mass of a 3-jaw universal chuck installed, from 685 RPM, so they are not dragging.

BUT, 685 is far from top speed, and I'd expect heat to be non-linear. If/when I try to turn faster...???

 

[itsme_Bernie]

Ok. First thing- you don't need to oil that much. It only needs a few drops at a time. If you can believe it, a lot of oil can make your bearings warmer! But again, you are not close to having your bearings be too warm, or even hot.

Second- especially since you want to run your lathe at somewhat higher speeds for longer periods of time- you should make the small investment in some actual light spindle oil. There are sellers on Ebay who sell small quantities for $15 (if memory serves me) for two bottles each of Mobil Light Spindle oil, and Mobil Vactra 2 for your lathe ways. DO this. Especially because you should be using much less anyway ... So no worry to use it up so fast. That 20W oil is just too thick, has no time to get out of the way of those Timken rollers after a certain speed, especially that much 20W oil.

It is good you were using non-detergent, as that is the most important issue with auto oils (the detergents keeping grit suspended, and no filter in the system). But a light spindle oil is really best for your machine.

Oils and oiling become somewhat fundamentalist, almost religious type of argument on machine forums, so I will qualify my statements here as "my humble opinion".

Also- be careful about turning a chuck at the top speed of your lathe, if you ever do. NOT all chucks are rated for 3000 RPM.

I have run my 618 at top speed for a little while at a time a while ago. My eyes were wide, and I was on my toes, but all was well.


Bernie

 

[cdhknives]

I bought a gallon each of Mobil Way Oil and Spindle Oil the first time I ordered from Enco...and my Dad promptly claimed the spindle oil for his babbit bearing Atlas 10D.:whistle:Whatcha gonna do!?!?!?)

Next order I'll get more but until then I do read some agreement that non-detergent 20W is about right for this lathe. I shoot a squirt into the oil cups before I start it and it runs down quickly. I give another shot every 15-30 minutes as I remember.

I just need to avoid a runaway heating/bearing trashing event. Right now my (limited) budget is going into tooling!

Oh, and no I don't normally run that fast, but I was trying to get a good cut on the alignment rod to check tailstock alignment (thread elsewhere) and spun it up a notch. I find the 266 RPM setting best all around and the 418 for finishing cuts...but I'm a rank amateur at this!

 

[8ntsane]

I have to wonder, were you using the tail stock while doing this machining operation? If so, it is possible to have to much pre-load on it. Many people forget the work piece expands, and when using a centre in the tailstock, it will push against the headstock bearing. The tailstock when in use should be re checked after warm up. Maybe not your problem, But thought Id mention it anyway.

As Bernie has already mentioned, you should expect some heat off the bearings. It would depend a lot on how the preload was setup, and what climate it was used in before you got the machine. Many machines have the bearing preload adjusted for a rise of 20 to 30 degree over room temp @ top speed after running for a 1/2 hour. Others would ajust the temp rise for the high speed mostly used. But, this gets into a whole different topic.

If you have a temp gun, you could check to see just how hot things are getting. Im not sure if over oiled bearings will generate excess heat like a bearing that is over packed with grease will, it maybe possible though. I have allways adjusted preload for a 30 degree rise above room temp at top speed. Have not had any bad effects doing so. I have seen many lathes run to little, or have never adjusted the spindle bearings, and have issues with poor surface finish though.

 

[cdhknives]

Interesting thought...yes I was working a rod between centers and I did have the tailstock cranked out pretty firmly as I was working right up to both ends and trying (successfully) to use the dead center friction to drive the (aluminum) rod for very light cuts. A 15 degree or so rise sounds about right. It was hot in the garage...South Texas in July...but it wasn't 120 degrees for sure.

IIRC on the Atlas 10F the right HS bearing is a cone/thrust bearing and the left bearing is parallel/axial load only? That might also explain the right bearing only warming up.

 

[8ntsane]

Ok, that's most likely where the extra heat you experienced came from. You might want to put a drive dog on your list as a project. Or buy one for jobs that require you to work between centres. Driving with friction such as you did can apply a lot of force to the bearing on the RH side of the HS. Not knowing you lathe, I wouldn't know what type of bearing arrangement it has. I think in most cases while in use, you will find the RH side does run hotter than the left. Most of us cut towards the chuck, and that alone loads the bearing more. You mentioned cutting aluminum, that stuff grows pretty good when it gets hot. Depending on how robust the headstock is built, you might want to be carefull on how much pressure you appy with the tailstock. I have buggered up a few live centres over the yrs, the rotating bearing type mounted in the tailstock.Though not very high quality live centres, from china. Doing jobs on aluminum shafting, but taking heavy cuts, and not re setting the pressure on the tailstock quill. The bearings on a cheap live centre didn't live through it. Just saying there is a lot of force going on there, even more if the work piece gets hot.