Be true to Babbitt or go with ball bearings?

I have an older 8" Porter woodworking jointer with a two blade head and two Babbitt bearings. The tables are rusted with disc sander marks. I am going to have them reground. I may replace the plain cutter head with a helical head. I am reworking this machine to be a shop tool not a museum piece. I am thinking of replacing the Babbitt with high quality pillow block bearings. My question is will a ball or roller bearing set up be better than nicely fitted Babbitt bearings? Before you blast me for destroying the antique value of this machine please be prepared to make me a nice offer on it.

Danny D said:

I have an older 8" Porter woodworking jointer with a two blade head and two Babbitt bearings. The tables are rusted with disc sander marks. I am going to have them reground. I may replace the plain cutter head with a helical head. I am reworking this machine to be a shop tool not a museum piece. I am thinking of replacing the Babbitt with high quality pillow block bearings. My question is will a ball or roller bearing set up be better than nicely fitted Babbitt bearings? Before you blast me for destroying the antique value of this machine please be prepared to make me a nice offer on it.

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I don't see what you gain by making the conversion. IF you are attentive to the lubrication Babbit works fine. Pillow blocks may be self aligning, and will work at higher speeds, but if you aren't speeding the thing up, the only 'benefit' is reduced attention need to lubrication. Babbit bearings aren't very happy if you run them dry.

Without knowing much about this specific application, I don't want to make a reccomendation, but it might be worthwhile to list some of the pros and cons of both bearing types.

1 - babbit (oil film) bearings: These work because the fluid gets dragged into a wedge shaped cavity by its tendency to stick to surfaces. The wedge shaped cavity is formed by the shaft being offset slightly from the exact center of the bearing shell(s). They are capable of supporting very large loads as long as the shaft is spinning fast enough to drag enough fluid into the space between the shaft and the bearing shell. Think about automotive connecting rod bearings. The fluid supports the load, no metal to metal contact occurs when running.
Pro: large load capability, high speed, don't need hardened shaft or bearing.
Con: needs constant fluid supply, can't support loads at slow speed, somewhat arcane rebuilding procedures, needs to be aligned.

2-The pillow blocks will have ball or roller bearings (sometimes called "anti friction"). These work by introducing a rolling element between the shaft and the outer bearing shell (race). All the load is carried on a very small area of metal rolling on metal. The balls or rollers rub against each other (in opposite directions) or else against a retaining cage that holds them in place.
Pro: can operate a low speeds, need only regular occasional grease or oil application, easy replacement of manufactured components, can tolerate misalignment if spherically mounted.
Con: depends completely on hardness of bearing materials & high degree of surface finish, fails rapidly if load levels exceeded.

So that ought to kick off the discussion.

If you know how to pour babbit bearing liners, I personally would go for that, since you basically have a high load / high speed bearing you can renew indefinately.

If you know your load and speed requirements, you can probably get off the shelf pillow blocks that will do what you need, but you might want to get some spares, and I would not scrimp on quality!

I don't know what sorts of loads are applied to a jointer shaft, but if you know the HP of the motor you are going to use, and the mass of everything that is spinning, you can probably work out what the max possible loading is, if say, you make some assumptions about the max feed rate, or if you stall the cutter suddenly.

Sounds like an interesting problem, might be difficult to actually calculate the specs needed, perhaps looking at a modern jointer of larger HP than what you plan to operate at and simply stealing the bearing part numbers?

Good Luck
- JC

JC- Where are you getting this high speed concept with babbit? Automotive engine bearings receive a constant flow of pressurized oil. Yes in this case, the parts never touch and everything is on a pressurized oil film.
Babbit bearings exist in boundary layer lubrication, where the oil is in a state of shear and this produces a lot of drag, and heat, and thus limits the speed. I don't believe no pressure lube babbit bearings ever get up on the oil, if only a little. And if they are warn at all, bets of proper lubrication go south rather quickly.
A lathe spindle with babbit bearings sucks.
A lathe spindle with pump pressurized bronze or iron shell insert bearings would be sweet.
That is what I have come to know about babbit bearings.
I would retro with ball or timken bearings.

--Doozer

Hokayyyy......I'll throw my two bits in. Are the present babbit bearings in removable shells of some sort? If so, replace with modern high speed bearings and carefully save the old shells wired up under the machine someplace.

Collector comes along in ten years and screams about destroying an antique.......you produce the original parts for restoration. You're a hero!

No one has yet mentioned dimensions.

In my experience there usually isn't room to replace a babbit/bushing bearing with any rolling element bearing, except needle bearings and they aren't worth a dang at high speeds, or the low clearances needed for woodworking machinery.

Most ball bearings are going to be substantially larger in section than a comparatively rated babbit equivalent.

Dave

The oil pressure in a babbit bearing has nothing to do with the supply pressure required to feed oil into the bearing. As an example oil pressure in an automotive engine is perhaps 75 psi but the bearing load pressure will be up to 7000 psi or greater. This pressure is developed by the velocity difference across the thickness of the oil film and the eccentricity of the center of the shaft relative to the center of the bearing. A flow of oil may be necessary to cool the bearing at high speed but is not required to support the load.

Johnhb

It's all about pragmatism. If you keep the old cutter head, retro fitting with BB would add expense and complication without substantial gain (other than that you could forget to lube more often). If you keep the old head , the shafts would probably have to be turned to fit a BB. If they are all scored, maybe this would be good. If only typical light Babbitt use scoring, then _lightly_ polishing the shafts, removing some shims, and retightening the bearing caps should make it good to go for another few decades.

If the bearings are sloppy and there are not enough shims left to remove and take up the clearance, then maybe turning the shafts and adding BB blocks would be more efficient. But you can always re-pour the existing bearings, too, without too much trouble.

If you get a new cutterhead, it might make sense to go with matching ball bearings at the same time. The alternative is to make the new shafts oversize for existing Babbitt, and then scrape in the shells, re-establishing alignments with the rest of the jointer. Properly set up & routinely lubed, it will be decades before much further work is required. But a Babbitt system does consume the shaft as well as the bearing over time. In a BB system, only the more or less easily replaceable bearing is consumed (and to some extent the housing, from fretting and cumulative effects of differential expansion forces). Of course a poor set of ball bearings, poorly fit, with substandard shaft attachment system can chew up the shaft, too. But let's assume a good set up.

Neither process is necessarily "better" and neither is particularly difficult. But one might be more efficient for you circumstances than the other.

smt

I'm no expert, but I recently completed a restoration of an old grinder with babbitt bearings which began with a question on this forum about correct lube for same. I ended up pouring new bearings and making a new shaft for the grinder. I recieved lots of assistance here and by someone who is into antique wood working machinery, in this case a planer. Here's a link to the thread, some of which will be irrelevant to your situation, but pay close attention to the links in some of the responses and you'll see the shaper and the bearing repair done by that gentleman on his planer: http://www.practicalmachinist.com/v...82843.html?t=182843&highlight=Babbit*Bearings
In his case he was able to rescrape his bearings and tighten clearance by removing shims. I have no shims in my bearings, so mine were repoured and scraped for clearance. I was also advised to use a particular oil called "PB&J" oil, for Pin, Bearing and Journal oil from a company called Green Velevet. This outfit makes oil specifically for steam locomotives and old "open bearing" machinery. The proprietor, Bill Petitjean, is a very helpful soul, very friendly and really knows his stuff. I believe if you stick with babitt and proper lubrication, the machine ought to last and last. Though I disagree that pouring babbitt can be done with minimal effort. I found it to be very labor intensive; not the pouring part, but the fixturing and scraping. I found everything to be readily available, though, from various sources. I'll be happy to share that stuff with you if you want.

We bought a 1907 Fay and Egan 24 inch planer about 6 years ago. Its a two blade square head running babbit bearings. Keep it running within its normal rpm range and well oiled and it should last another 100 years.
Babbit is not a high speed bearing.
If you change to a round, gib type cutter with more blades, you shouldnt need to change the rpm.

Babbitt not for high speeds and loads? That would be news to the power generation industry where rotors weighing hundreds of tons are routinely operated at 3600 rpm. With loads of this mass oil must be fed at a high volume ( maybe because a 30 inch journal 24 inches wide needs a lot) and pressure. I think your situation is a little less demanding. I'd go babbitt.

I would go with Babbitt.

"....rotors weighing hundreds of tons are routinely operated at 3600 rpm...."

You will have to prove that one to me. Are you sure its not 360 rpm?

--Doozer

I talked with an old guy who helped install the largest (at the time) rotors GE had built. Yes, it is 3600 rpm. The rotor/stator clearance was on the order of .030 at diameters up to about 13' IIRC. He said balancing took "awhile". I would've loved to be fetching tools or water for them.


Charlie

tdmidget said:

Babbitt not for high speeds and loads? That would be news to the power generation industry where rotors weighing hundreds of tons are routinely operated at 3600 rpm. With loads of this mass oil must be fed at a high volume ( maybe because a 30 inch journal 24 inches wide needs a lot) and pressure. I think your situation is a little less demanding. I'd go babbitt.

Click to expand...

I was thinking similaraly. the only babbit bearing I ever scraped was
on a 6 inch shaft and about a foot long on a rock crusher. We cooked up
20 lbs of babbit in a cast iron pot and were going to ladel it in to pour the bottom half. IT quickly became apparent that our ladel was way too small for the job, so we upended the pot and dumped it in.

It took me most of 1 day to scrape it enough that it would run without
heating.... the main issue was to take down the high spots so the weight of the crusher shaft/jaw and flywheel (several tons) was disbursed over
a wide enough area

Born2L8 you are rt on. Most generating plants operate at 3600 rpm. Early gas turbines ran at 4600 or so and were geared down to run the generator at 3600. The biggest of the big, nuke plants, are so big that the low pressure rotor tips are pushing supersonic at 1800 rpm. Of course they are over 18 feet in diameter. The last one i worked on(6 weeks ago) the total turbine weight(2 HP and 3 LP was about 500 tons on 9 bearings. The main generator rotor ( which we changed out) weighed 411,000 lbs and rode in 2 babbitt bearings.
Prove it to you? Took me a week to get clearance to get in there . If you are not there on biz and sponsored by a contractor, forget seeing it. I don't know if this info is available on the web anywhere( I couldn't find it), but I don't see why it should be secret.
At any rate almost all power plant equipment runs at 3600 rpm, unless diameter prohibits it. These machines usually have a lift oil system, basically a hydraulic pump to provide oil pressure to raise the rotor off the bearing. When up to speed the volume pump takes over and the journal runs on a wedge oil created by it's rotation. They typically last for years and years unless there is a failure in oil supply or there is contamination.

Wow, that is something. I would have thought the hoop stress would cause it to burst.
I guess I was thinking of a cast iron flywheel.
Steel is some amazing stuff.
I still can't fathom how big airplanes fly and how indy engines spin at 20,000 rpm.
--Doozer

I bought a Parks 4" X 12" Parks Wood Plane in Los Angeles in 1972 and cleaned it up and painted it for use in my then guitar shop. I replaced some worn bushing in the gearbox and had the three blades sharpened. Other than that it was in good running condition.

It has babbitt bearings for the rotor bearings. There is a grease fitting on the bearing on each side. They were in good condition when I got the machine so I merely cleaned the bearings and put them back in.

I used it very heavily when I was building and repairing guitars and doing other woodwork from 1972 through 1985 and the bearings were still good the last time I looked at or ran the machine a couple of years back.

It has a 2 hp 220 VAC 1750 rpm single-phase reverse induction Emerson motor that's the size of a small watermelon. It has a large pulley on it and the ratio to the rotor pulley provides something like 4,000 rpm on the rotor. With three blades that's approximately 12,000 cuts a minute.

To make a long story short, I always thought that Babbitt did pretty well at high speed if it was properly lubricated. I thought about having ball or roller bearings installed when I was originally working on the machine but it didn't seem like it would provide any benefit. Also, I was concerned about modifying a machine that I was told dated from 1940 or so and which was completely original, including the original metal stand.

My 2 cents and a vote for Babbitt!

high pressure lube to bearings is a completely different realm than the drip oil we normally associate with old machinery journals.
One spindle system i worked with at Ingersoll ran 25 000 rpm turning 65 hp - hsk 63 and
hsk 100 spindles. They were bronze bearings with 1100 psi velocite 3 oil. There was .0015/ .0018 gap between the bearing surfaces when there was no oil pressure and tons of slop. Turn on the oil and there was no end play side play.

tdmidget said:

Born2L8 you are rt on. Most generating plants operate at 3600 rpm.

.....

At any rate almost all power plant equipment runs at 3600 rpm, unless diameter prohibits it .

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There is a really good reason for this. they want 60 cycle power and that's the way you get it. they can run slower than that by double winding and the like but it has to be a speed that is can be evenly divided into 3600
such as 1800, 1200, 900 etc.

the modern exception to that is being used in windmills now where the
VFD technology is used in reverse to produce 60 cyle power from what ever
speed the wind turbine is turning.

Indeed the technology contemplated for ocean wave generation doesn't even spin. they plan on using linear fields which are exercised by anchoring
a bouy to the ocean bottom and letting the top part float.

the vision is to collect the spurts of power produced by the linear extension
of the bouy as a wave causes it to float up, and with the use of VFD technology assemble those spurts into usable electric power.