Headstock bearings

[nitris223]

I was turning down a stress proof steel last night at 1400 rpm . I was set up using the livecenter and the dead center. After I finished a pass I shut off the lathe to take a measurement and I noticed that it had stopped very quick. Alot quicker then normal. The headstock area felt very warm , could this be a sign of the bearings going out. I did have the centers snugged up pretty good and was cutting towards the headstock so all the force was going towards the bearings. It has seemed to be a bit louder then normal but I have heard that the gear head drives are louder then belt drives.

It calls for 68wt oil in the head stock what would happen if a guy ran 100 wt. Would it be harder on the bearings. I was thinking about trying this 100wt the next time I change the oil.

[Fasttrack]

What type of lathe do you have? Are we talking about roller bearings or sleeves? Sounds like they must be roller bearings.

The spindle stopping quickly with roller bearings is not neccessarily a sign of failing bearings - more likely it stopped quickly because you had a high thrust load on it (even once you shut it off).

[BadDog]

Did you have it really tight, and then get it hot? That effectively increases the preload and will make it stop quick, and heat up the bearings/headstock. If this is it, I'll be the live center was also suffering. Have you tried it again with the piece out?

[Boucher]

Why change

Use the oil the Manufacturer recommended.

In basic lubrication principles the thinner oil is going to work better.

[nitris223]

come to think of it the live center was a little warm to the touch. I did try a few more passes and at one time I did notice about half way through the pass that the piece was starting to slow down and could actually hear it slowing down. Sometimes it would freewheel and other times it would stop in about 6 revolutions.

Fasttrack the lathe is a chinese lathe. Bascially the same as Grizzly , HF, BusyBee, King tools. They all look the same in pictures but I am sure there is a quality difference between them. It is a 12x36 Force brand name. I bought it local to me just for piece of mind if service or parts were needed and I wasn't making phone calls across the country trying to describe parts and such and loose alot of downtime. Turns out 5 months after owning the lathe the company goes under and closes all the stores in three provinces. So now if I ever need parts it should be a real treat. Murphy's Law in effect.

[lakeside53]

Put the headstock in neutral (or between gears) and turn it by hand. Is it "tight" or can you feel tight spots? If so, definitely investigate further. As for warm - not unusual even for a correctly preloaded spindle. If it seem o.k., run the lathe at high rpm for 20 minutes while monitoring the temperature increase near the front spindle and rear bearings.

Lube - Does it call for SAE68 or ISO68.. and "non-detergent motor oil" or "gear oil"? ISO 68 hydraulic oil (common in many lathes) is roughly equivalent to 30 wt SAE. If the lathe in fact calls for ISO 68 and the prior guy didn't know the difference, and put in a much heavier engine oil, it wouldn't be the best for higher rpm.

[nitris223]

It calls for ISO 68. I was thinking ISO 100 would make it a little quieter but I don't want to cause any problems .

[MTNGUN]

It calls for ISO 68. I was thinking ISO 100 would make it a little quieter but I don't want to cause any problems .

I've got a couple of 12x36's. I run whatever oil is on sale, don't remember what I put in last time, don't care. Bearings will run on oil or grease, they are not picky at moderate speeds as long as they do have clean lube.

However, the important thing is to keep enough oil in the gearbox. Instead of the middle of the sight glass I keep it near the top of the sight glass with the lathe idle (the level drops when the lathe is running because lots of oil is slung onto the walls of the tank, etc).

I used to run with the oil in the middle of the sight glass because that is how sight glasses normally work. Worked fine at normal speeds. However one day I had been running at high speed and, like you, noticed the spindle was hot. It also turned a little rough. I noticed that when the lathe was running, there was no oil in the sight glass.

I've never taken the gearbox completely apart, so I don't know this for a fact, but when you peer into the box from above, you only see one gravity fed oil hole ABOVE the spindle bearing. Perhaps there is another oil passage below, I don't know. However, it looks like it wants and needs splash lubrication from above to drip down into that oil hole. That means the oil level needs to be high enough to ensure a continuous splash.

I suspect that because the oil level drops when the lathe runs, the bearings may not be getting enough splash lubrication. The solution is to raise the oil level to near the top of the sight glass. Worst case, you'll waste power churning gears through the oil, but at least there will be plenty of lube.

By the way, I'm still running those bearings, though I avoid high speeds. Runout seems OK. One of these days I'll have to replace the spindle bearings, but for now they are chugging along.

[MTNGUN]

I'm in the shop now and I looked at the oil level and how the spindle sits relative to the oil level.

The spindle bore is approximately 3" above the oil level.

That means the spindle bearings DO NOT HAVE AN OIL BATH. They must be totally dependent on splash lubrication. If the level drops too low, there will be little or no splash.

Just keep the level near the top of the sight glass. Better too much oil than too little.

Sounds like you are up for new bearings. I feel your pain.

[nitris223]

Just got back into the house from checking out the oil in the lathe. I figured I would drain the oil and put new stuff in just to be sure. Second oil change since new last year. Maybe 60 hrs on the lathe. I did notice that the oil was a little down . Sight glass sucks big time, it was showing oil in the middle and it was actually below. The gaskets and seals kind of suck also, they leak a little bit of oil . I have removed the gear change covers twice and made new gaskets and also put on gasket maker as some extra protection and they still leak a bit. I will live with it for now. When I filled up the gear case I noticed that the oil level when set to the site glass level was just touching the bottom of the gear next to the spindle bearing . Knowing that this is a splash type system it is not going to get much oil. I filled it above the top of the sight glass about 1/4" which puts the gear about 1/2" into the oil. Sight glass still shows in the middle. I made up a dip stick to check the oil level from now on.

Picked 1200 rpm gearing and fired up the lathe with no load just the chuck mounted. Did a 20 minute run and took temperature readings on the front and back spindle bearing covers. Front and back started at 70 degrees and climbed to 94degrees slowly and settled out around 15 minutes. Back bearing was 96 degrees , I could get a better reading on the back one so I would think the front would be about the same temp. I will try it later tonight amd make some chips and see what the temps do under load.

[EVguru]

On my Harrison L5 there is a groove on top of the front wall of the headstock. Oil flung up from the gears is collected in this groove and then dribbles through a hole positioned between the spindle taper bearings (passing a magnet on the way).

[Machtool]

I was turning down a stress proof steel last night at 1400 rpm . I was set up using the livecenter and the dead center.---- I did have the centers snugged up pretty good

Just guessing here, but it sounds like that shaft had some length to it. You are aware that as the shaft gets hotter it grows in length? 1,400 rpm, if you weren’t flooding it with coolant when you where turning it, a snug centre, will go very tight as the shaft heats up, increasing the thrust on the spindle and the centre. Kind of a common problem if you lock the tailstock barrel.

Regards Phil.

[lakeside53]

Picked 1200 rpm gearing and fired up the lathe with no load just the chuck mounted. Did a 20 minute run and took temperature readings on the front and back spindle bearing covers. Front and back started at 70 degrees and climbed to 94degrees slowly and settled out around 15 minutes. Back bearing was 96 degrees , I could get a better reading on the back one so I would think the front would be about the same temp. I will try it later tonight amd make some chips and see what the temps do under load.

I'm betting you'll be o.k... my lathes get a lot warmer than that ( I run them at 2000 for the test). it would be a good idea to put your oil back to IS068. My big lathe runs IS032; the smaller - ISO22.... both max out at 2500 rpm.

[MTNGUN]

When I filled up the gear case I noticed that the oil level when set to the site glass level was just touching the bottom of the gear next to the spindle bearing . Knowing that this is a splash type system it is not going to get much oil. I filled it above the top of the sight glass about 1/4" which puts the gear about 1/2" into the oil. Sight glass still shows in the middle.

Sounds like you got if figured out.

No oil pump, no oil bath, just splash into what I remember as a rather small hole.

At the time I had my "incident," I think the oil level may have been below the center of the glass. Either a little had leaked out, or I was short the last time I had changed the oil, something like that. I wasn't concerned because normally mid-glass means "perfect" and low-glass means "add a quart".

But not on the 12x36. Mid-glass means "barely adequate" and low-glass means "fried bearing."

Getting back to your original question about oil viscosity, this is my take. The 12x36 has sloppy straight cut gears. They are noisy and the slop can contribute to a poor finish on the workpiece. I like a thicker oil because it cushions the gears and reduces the noise a little. Don't remember what I put in last time but it was probably a light gear oil.

The bearings aren't picky about oil as long as they have it. If you put seals on the bearings and packed them with grease that would work fine and I imagine the belt drive version of the 12x36 did use grease. The point is, they are not picky about the viscosity of the lube. The gears, on the other hand, benefit from a sticky, viscous lube.

[ldbent]

Self tightening

I have to agree w/machtool, i.e. the heat generated by metal removal caused the work piece to grow in length and bind a bearing. Oil is oil. I use 46 weight hydraulic oil that I buy in 5 gallon pails from Tractor Supply Company or from my local lubricant dealer. I use it for everything. I wouldn't use a heavier oil as the rolling elements of the bearing may force the lubricant from the bearing. Pressure lubrication is often considered better than splash because oil foaming is nearly eliminated. Enco has some Vactra II on sale now with free shipping.