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Finishing Babbitt Bearings

jeff10049

Aluminum
Joined
Oct 24, 2009
Location
Central Oregon U.S.A.
This is another automotive question but should be relevant as many old machines use Babbitt.

Is it acceptable to sand or hone a babbitt bearing? I assume NOT as I would be concerned about it doing its job and embedding the grit. Then it could act like a lap on the new crankshaft or, can it be cleaned well enough to remove the grit and be ok?
This is not a two-piece bearing so scraping is not really feasible as far as I know. It's a sleeve bearing 1.260 Dia 3.5" long. I line bored them and hit my numbers dead on except for one I got my numbers mixed up and need to remove about .0003. I did not catch this until I broke down the line bore setup. I don't think that I can reset the line bore without some alignment difficulty and this is such a small amount it would be tough to pull such a fuzz of material on a re-setup. There must be a safe way to shave off a few 10th's.

I have heard some interesting things like steel wool it seems as bad as abrasive little strands of steel embedded maybe they don't? Fine mesh screen sounds intriguing and might work. And plain ole paper it does polish a babbitt bearing nicely but I wonder about actually removing a measurable amount of material in a timely and consistent manner. I suppose a reamer could work but sounds scary we're talking a few 10ths in soft material. I have heard of Timesaver I guess it's not supposed to embed in the bearing I could get some make a mandral and lap it with that if there are no better ways. But I also question the timesaver claims what makes it safe?
 
Hand scraping would be the simplest ......the tiny amount to be removed shouldny take long .......you can scrape lengthwise with a part circle blade on a long handle ..
 
I have heard some interesting things like steel wool it seems as bad as abrasive little strands of steel embedded maybe they don't
I have a engine rebuilds in my complex who rebuilds high end vintage engines. He uses really fine steel wool. I know because he nicked mine. :D
 
I would not worry about .0003" and would just go with it, it will wear in very quickly. If you just have to remove it, buy a cheap brake hone that you won't care that it gets Babbitt imbedded in it and hone it for a few seconds.
 
I think the reason cylinder hones are typically not used is they follow whatever shape is there. If the bearing is egg-shaped, they will just make it a larger egg. printing and scraping allows you to take just the high spots out. You can bore it or ream it too and get satisfactory results, but where the bearings often are (big or weird shaped castings) means that by the time you get it on a machine with your cutter lined up or make a piloted hand reamer for a one time use, you could have scraped it by hand and been done. The scraped cut also provides better lubrication retention between the surfaces then if they were honed or reamed, but I think that might only make a difference in higher speed plain bearings using thinner lubricants.
 
I would not worry about .0003" and would just go with it, it will wear in very quickly. If you just have to remove it, buy a cheap brake hone that you won't care that it gets Babbitt imbedded in it and hone it for a few seconds.
I Should have been more specific it's tight about ,0002 so it won't go on the shaft you could maybe gently tap it on but being 3.5 long if it hung up or stuck that could end badly. This engine is set up with initial clearance of slight drag after run in most guys end up with about ,0007 - ,001. Right in spec.. when I was line boring my bore gauge was indenting the soft babbitt about a .0001 so was shooting for a ,0001 or so over. For some reason I stopped .0001 under add the indent of .0001 and it's just a little tighter than I want to force. I am aware that sleeve bearings can be scraped length wise but my skill level and the tiny amount I was looking for other options. It sounds like honing may be more of an issue with the hone embedding babbitt than the other way around.. I have a junk bearing on the bench I'll play around with that some today.
 
To my knowledge, the only abrasive used to 'bed in' or fine-finish babbitted bearings is "Timesaver". I believe this is a very fine powdered pumice. The pumice polishes off any very small high spots on the babbitt, but as an abrasive, breaks down quickly. As a boy in the 50's and 60's, I can recall older men talking about speeding up the 'breaking in' of a new car engine by pouring some household scouring powder into the crankcase. At the time, this idea sounded nuts to me. Years later, Mike Korol, an erecting and field service engineer for Skinner Engine (unaflow steam engines) told me about "Timesaver". Mike said when he'd get done erecting or overhauling a steam engine (marine or stationary), he did two things to help break in the bearings:
-with the bearing clearances set up on the tight side & no oil in the bearings, the engine was jacked over for 2 full revolutions. The idea was the journals would burnish the babbitt, a cold working process. This would improve the surface finish on scraped bearings and get rid of any miniscule burrs or small high spots left from the scraping.

-after the 'burnishing', a container of "Timesaver" was dumped into the engine's lubricating oil sump tank. The engine was started under steam at low speed, and the Timesaver was mixed and circulated with the lube oil. The engine was worked up to its operating speed and 'put on the governor" and let run for awhile. Bearing temperatures were scientifically monitored by using the back of one's hand. A 'heat run' was done with the Timesaver circulating with the lube oil. The bearings would 'bed in' to the journals and bearing temperatures might drop off slightly. The oil with the Timesaver was disposed of, another charge of lube oil was run for a short time with the engine under load, and this oil was also disposed of. That flushed the engine of any remaining "Timesaver".

When I was working at a large pumped storage hydroelectric powerplant, I was involved in having numerous bearings rebabbitted and scraped in. These were segmented shoe type bearings and large flat 'pie shaped" thrust bearing 'shoes'. We sent these bearing shoes out to various babbitting shops. Afgter machining the new babbitt to correct geometry and scraping oil 'leads', we'd get the shoes back to our powerplant from the rebabbitting shops. We'd do some final 'scraping in' with our own plant mechanics. One trick we learned from several of the rebabbitting shops was the use of fine "Scotchbrite" pads to polish freshly scraped surfaces. We did a lot of hand scraping and did some power scraping with the "Biax" power scrapers. Scraping leaves tiny burrs. Prior to the use of Scotchbrite, we'd take the edge of a lathe parting (cutoff) tool blank and use it as a draw scraper. Same idea as a woodworker's cabinet scraper. This type of scraping did what we called "giving the babbitt a close shave, taking off the fine whiskers". After this 'fine shave" (and later, the use of Scotchbrite), the babbitted surfaces were cleaned with solvent and white wiping cloths. The white cloths often came away with silver-gray staining from the babbitt dust on the bearing surface. Steam engine and Hydro electric turbine and generator bearings are a totally different proposition than automotive babbitted bearings, but that's where my own experience is based. Much looser clearances and tolerances than auto engine bearings. However, if we consider a steam engine main journal at 14" diameter by maybe 18" long, or the hydro turbine journals as big as 60 inch diameter, those seemingly 'loose" tolerances and clearances against the larger journal diameters are closer and tighter than what they first appear to be. In the days when auto engines had babbitted bearings, I know loose shims were used to set clearances on the crankshaft main and con rod big end bearings. While I have n o experience with these type auto engines, I know the auto industry made the move to insert type bearings and that 'tightened up' bearing clearances and manufacturing tolerances. Seems to me that an auto engine built with poured babbitted bearings relying on 'scraping in' the bearings and using loose shims is likely built with clearances and tolerances measured in thousandths of an inch. With the move to insert type bearings, closer bearing clearances, tighter manufacturing tolerances, working to 'tenths' being the new norm.
 
Thanks for all the suggestions. I have also heard of using scotchbrite on bearings it's probably fine but I decided to avoid abrasives. I did something similar to what Joe Michales described above with the parting blade. I had not thought of draw scraping the full length at once I clamped an olfa break-off style knife blade between two parallels blued up the bearing and scraped off the blueing it worked well two rounds of that and it fits the shaft and has very good contact. It's nice to have the crankshaft fitted I'm back to where I was a year ago when I discovered my stock crank was junk and began the long process of having a small batch of them made.
 

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I Should have been more specific it's tight about ,0002 so it won't go on the shaft you could maybe gently tap it on but being 3.5 long if it hung up or stuck that could end badly. This engine is set up with initial clearance of slight drag after run in most guys end up with about ,0007 - ,001. Right in spec.. when I was line boring my bore gauge was indenting the soft babbitt about a .0001 so was shooting for a ,0001 or so over. For some reason I stopped .0001 under add the indent of .0001 and it's just a little tighter than I want to force. I am aware that sleeve bearings can be scraped length wise but my skill level and the tiny amount I was looking for other options. It sounds like honing may be more of an issue with the hone embedding babbitt than the other way around.. I have a junk bearing on the bench I'll play around with that some today.
Whoa!!!!!!!!!! That bearing should have .001 to .0015 clearance! You are way off. At least you have too much material rather than not enough. Hone or lap that rascal to the proper clearance.
 
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My immediate question is if the boring job is up to snuff, finish good and bore straight and round, and you were .0003” tight , why not just polish the crank.
That crank is likely soft and ground to just clean up ( no specific size)
So why not just polish it. No issues with Babbitt grit embedding, or on making the bore less than true by uneven scraping. Correct the shaft. You’re not looking to make a big change.
Cheers Ross
 
Factory spec on 1.9 liter vw tdi alh engines and several others was 5 tenths to 25 tenths for the connecting rod clearance. This is about 2 inch diameter bearing. Red line around 5500 rpm.

They tend to fail 30 minutes after they run out of oil.

Surface grinder spindles running oil thinner than diesel would need tolerances on the order of 3 tenths.
 
My immediate question is if the boring job is up to snuff, finish good and bore straight and round, and you were .0003” tight , why not just polish the crank.
That crank is likely soft and ground to just clean up ( no specific size)
So why not just polish it. No issues with Babbitt grit embedding, or on making the bore less than true by uneven scraping. Correct the shaft. You’re not looking to make a big change.
Cheers Ross
It is ground to size but of course it doesn't need to be. It is also relatively soft. The draw scraping seemed to work well.
 
Whoa!!!!!!!!!! That bearing should have .001 to .0015 clearance! You are way off. At least you have too much material rather than not enough. Hone or lap that rascal to the proper clearance.
Hi tdmidget, I have learned through experience on this type of thicker non non-adjustable babbitt to shoot for near-zero clearance. The max clearance called out is .0012 There is a certain amount of break-in that occurs even a mirror finish line bore job has some peaks and valleys as we all know. There is also a certain amount of compressibility that occurs with the babbitt. I try and limit that by swedging the bearing into the bore it helps but you still get a little deformation/compression of material on running in. A tenth here and there adds up fast and with no choice but a repour and line bore if you end up on the big side. I sneak up on these very carefully this was the first time I undershot one on the line bore wasn't sure what to do but scraping despite my first thoughts worked well. I don't set them up as tight as the factory as they were a die-cast bearing that did not get a line bore, swedged, or scraped so they were put on tight and burnished in.

Early Chevy rods were set up tight if you could move it with anything less than a hammer tap it was too loose modern shops will set them up with plastic gauge at .0015 and 50 miles down the road you'll have a rod knock and need to set them properly then they run thousands of miles. A later chevy with the thin babbitt needs to have the clearance from the start or you'll ruin the bearing. A Ford block main bearing where you can pour and then peen it in while warm line bore and scrape to fit also should have clearance from the start. It depends on a few factors with these early cars I don't think too many shops or people can even get a babbitt bearing to last anymore. It's a shame when done right they offer great service mine were over 100 years old not the best design and still performing albeit worn out. I know from history that this car had a lot of miles.
 
Hi tdmidget, I have learned through experience on this type of thicker non non-adjustable babbitt to shoot for near-zero clearance. The max clearance called out is .0012 There is a certain amount of break-in that occurs even a mirror finish line bore job has some peaks and valleys as we all know. There is also a certain amount of compressibility that occurs with the babbitt. I try and limit that by swedging the bearing into the bore it helps but you still get a little deformation/compression of material on running in. A tenth here and there adds up fast and with no choice but a repour and line bore if you end up on the big side. I sneak up on these very carefully this was the first time I undershot one on the line bore wasn't sure what to do but scraping despite my first thoughts worked well. I don't set them up as tight as the factory as they were a die-cast bearing that did not get a line bore, swedged, or scraped so they were put on tight and burnished in.

Early Chevy rods were set up tight if you could move it with anything less than a hammer tap it was too loose modern shops will set them up with plastic gauge at .0015 and 50 miles down the road you'll have a rod knock and need to set them properly then they run thousands of miles. A later chevy with the thin babbitt needs to have the clearance from the start or you'll ruin the bearing. A Ford block main bearing where you can pour and then peen it in while warm line bore and scrape to fit also should have clearance from the start. It depends on a few factors with these early cars I don't think too many shops or people can even get a babbitt bearing to last anymore. It's a shame when done right they offer great service mine were over 100 years old not the best design and still performing albeit worn out. I know from history that this car had a lot of miles.
Every power plant has babbitt bearings in the turbines and generators. Plenty of shops make them last. Those shops are not worried about competion from you, i'm sure.
 
Every power plant has babbitt bearings in the turbines and generators. Plenty of shops make them last. Those shops are not worried about competion from you, i'm sure.

What do power plant bearings have to do with it? I am not very familiar with them, except that they are very different from die-cast, pre-war car bearings which is what I was referring to not lasting.
When you mention that plenty of shops make them last, I am assuming you are referring to automotive bearings. Can you provide the data and name these shops? how were the cars used? A poorly made bearing job that lasts 10,000 miles might outlast the owner of most babbit-bearing cars. However, the next owner might suffer the consequences. At any AACA meet, the consensus is that you have to convert to inserts if you want to drive your car because not many shops can make babbit bearings last. It is unfortunate because a proper babbit job can last. There are some good shops, but they are in the minority. Automotive babbit, in general, is the minority, and there are only a few good shops. There are a few more hole-in-the-wall shops that do a good job as well if you can find them.

Your comment about those shops not being worried about competition from me sounds like a jab at me. WHY? I am not even in the business; I do this for myself and the occasional customer, usually redoing a so-called babbit shop's crap job that failed in a few hundred miles. Nonetheless, the competition thing makes no sense. Why would anyone be worried about competition? The good shops are buried with work, and the bad shops will keep finding a new sucker or go broke. When I was in my teens, an old guy said, "Son, there is always room for somebody good." He was right.

You mentioned honing or lapping my bearing to what you think is the proper starting clearance. That was my original question. What do I hone it with? How do I clean it afterward? Can you cite examples of honed babbit by a certain method and prove that grit was not embedded, and no damage or accelerated wear occurred on the shaft post-honing? Just because Joe Six Pack did it and it worked for him, that does not work for me. It would be convenient to hone babbit occasionally, especially these small sleeve bearings. However, until I have proof of a safe way, I am not going to. I do not have time to experiment and test this out. My question was in the hope that this was already an accepted practice, but it does not seem so, and that is fine.

Since you are aware that plenty of shops do this and make it last, maybe you could ask one of these shops how they would babbit this engine, how soon they can do it, and if they provide a warranty? I am tired of redoing bad babbit jobs. My questions are:

How do they ensure the babbit is tight in the engine line bore front and rear?
How do they address the third main alignment?
How do they get a crush on the center main and still assemble the engine?
How do they handle the clutch thrust?
Can they assure me that if they set the front main clearance bigger than the factory spec of .0007, the 65# 14" flywheel hanging way off the front of the crank on an unbalanced engine will not cause any compression/burnishing/break-in wear of the babbit and increase in clearance resulting in excess clearance and a redo?

Next, how do they pour the babbited in-place cam?
What do they do to keep it from shrinking away from the housing?
How do they control cam warpage?
I have redone a few for broken cams all from different shops I guess they couldn't make it last.But what do I know?
How do they set the cam bearing clearance?
Do they do it the same on the front journal? If not, why?
What about the cam end play?
How do they cool their babbit after pouring?
What grade of babbit are they using and why?
Is all babbit poured new?
What pouring temp?

Lastly, I would like references not for parade cars and ice cream getters but from customers who tour their cars.
What do the bearings look like after the first 10k did they need to be adjusted?
I drive my cars so do my customers we don't have the time and money for crap-bearing jobs.


The engine I am referring to is a 1910 Golden Belknap and Schwartz 4-cylinder engine. It is common enough that the shops should know. Maybe one of those power plant guys could put little tilting pad bearings in it. Wouldn't that be cool?"
 
Jeff10049:

Here are a few generalized answers to some of your babbitting questions:

-to minimize shrinkage and get a good bond with the bearing shell, the bearing shell is preheated.
-older designs of babbitted bearings often included dovetailed keyways or blind holes in the bearing shells. This was to mechanically lock the babbitt in place.
-an alternative means of getting a mechanical 'interlock' between the babbitt and the bearing shell (or cast block) is to machine the surfaces to receive babbitt with
a coarse surface finish. In addition, an abrasive blasting with something aggressive (like "Black Beauty") to create a 'white frosted surface' also goes some ways to
creating a mechanical 'interlocking'.
-Prior to ultrasonic testing (to check integrity of the bond of the babbitt to the bearing shell), a common practice was to pour the bearings with a bore a good bit smaller
than finished diameter. If the bearing were a split bearing, the babbitt was then peened (cold worked) to make sure it filled the keyways or locking features on the
bearing shell. Boring to finished diameter was then done.
-For one-piece babbitted bearings, such as poured-in-place bushings, burnishing with a tool similar to a condenser or boiler tube roller was done. This cold-worked
the babbitt and made a harder surface for the journals to run on. Finish boring was then done.
-We experienced some cracking of babbitt on large powerplant bearings after years of service. This cracking seemed to follow the dovetailed keyways in the bearing
shells. This led us to some research as to why some babbitted bearings lasted for many years and others exhibited this cracking after much shorter times. The answer
lay in part in the alloying elements in the babbitt. The older babbitts for heavy service, aside from being "high tin" babbitts, contained small amounts of cadmium. With
cadmium being outlawed (or at least avoided) due to toxicity, the replacement babbits were formulated without it. We worked with one well known bearing manufacturer and repair shop to come up with a substitute for the cadmium. They made their own babbitt in house and used antimony as a substitute. I retired from the
powerplant, and it's been too short a time to have had things apart for inspection of bearing shoes or pads.
-cooling babbit after pouring on heavy bearings was what seemed a counterintuitive process. The idea was to get the babbitt and the bearing shell (heavy castings in
the work I was involved with) cooled down quickly. As soon as the babbitt had 'skinned' (begun to solidify on the exposed surfaces), nozzles blasted water at ambient
temperature against the bearing shell. During the pouring, gas burners were setup to keep flames against the bearing shells and keep the bearing thoroughly preheated. For that reason, the first time I saw the cooling water setup, I was somewhat in disbelief. There must be something to it as the turbine and generator
builder in Japan used this procedure, and some industry leading bearing shops in the USA also use this same procedure. The rapid cooling using water at
ambient temperature (the babbitt shops have large steel water tanks inside the shop buildings where water sits and comes to ambient temperature over
days if not weeks prior to use) seemed to be key.

-I am unfamiliar with the type engine and bearings you are working on. Are the crankshaft main bearings 'poured in place', or do they have removeable shells ? I've
seen some large main bearings on medium speed diesel engines which had removeable shells. These shells were made of bronze, split along the centerline of
the crankshaft. The babbitt layer in these shells was fairly thick. The shells were assembled in a fixture and babbitting was done using centrifugal casting. Shims at
split joint allowed the shells to be separated. The babbitted shells were then setup on a vertical turret lathe and bored to finished diameter. Oil grooves and oil
leads were put in after boring, and a final cleanup done using hand scraping and 'shaving'.

-a 'game changer' in babbitting work was the use of ultrasonic testing. This allows the bond between the babbitting and the bearing shell to be checked. When we'd accept a babbiting job, we'd always require U/T as well as a dye penetrant test at the edges of the bearing (along the interface where the babbitt met the shell).
A good babbitting job would show 100% bonding or very nearly so by U/T.

-tinning of the shells is another subject. Some of the bigger babbitting shops have 'tin tanks'. These are steel vats of molten tin. Shells to be babbitted are preparted by machining off old babbitt to expose virgin metal. This is then abrasive blasted, acid pickled, hot water rinsed, and dried using heat guns or similar. When the
shell is dried off, areas not to be babbitted are coated with a chalk wash. This effectively masks off areas where babbitt is not to be bonded. The shells are then submerged in the tin tank and spend a good while there. This gets a uniform temperature thru the entire shell. After this soaking time, the shells are lifted out
of the tin tank using stainless steel hooks or other devices or rigging fixtures. As soon as the shells are hanging over the molten tin tank surface, stainless steel
brushes and spatulas are used to level off and thin out the molten tin coating and make sure it fills all odd nooks and crannies (if the shells have dovetailed
keyways or blind drillings).

-Once the tinning is done, the shell is immediately moved to the babbitting table. Pre-made dams (sheet steel end closures), fixtures to hold a mandrel on centerline,
and damming compound are quickly put onto the shell. Gas burners are aimed at the shell and lit. This maintains the preheat from the tin tank. Babbitt is then
poured. Stainless steel rods are often used to work the molten babbitt if there are keyways in the bearing shells, to work up any possible trapped air.

-Centrifugally cast bearings are tinned, then setup in the centrifugal casting machine. Gas burners are lit and aimed at the bearing shells as they spin. This
maintains preheat temperature. Cooling is a matter of what the bearing size is and what the shells are made of. I've seen water nozzles used and I've seen
bearings cooled by simply leaving them spinning in the centrifugal casting machine until they reached ambient temperature. I've seen some diesel engine
main bearings centrifugally rebabbitted. These were somewhere around 10" diameter journals, heavy bronze split shells, maybe 3/8-1/2" of babbitt
centrifugally cast onto the shells. Obviously a different animal than the automobile engine bearings you are dealing with. Bronze shells made for an excellent
bond with the babbitt, and centrifugal casting gives a really good dense babbitting. Obviously, also, a medium speed diesel engine's bearings are not made to
the tight tolerances your auto engine main bearings require.

I believe I see your objective: your restoration/rebuild of the car's engine is being done to closer tolerances than originally used. This will enable the car to be
driven over longer distances and give a much longer service life than the original bearings provided. Given the age of the car and its engine, as well as design
(from what I see in your pictures), the machine work of that time likely produced an engine with looser fits and clearances. At that time, people expected short service life on auto engines. Pulling down the pan and reshimming bearings was likely a fairly regular occurance that car owners expected and dealt with. Your aim, unless I am off base here, is to rebuild/restore the engine so the car can be driven on tours, to meets, and similar without worrying about bearings starting to knock. I have marvelled at insert bearings, coming from my type of work. How so thin a layer of bearing metal, as well as so narrow a bearing width can do the job it does is something I think about when I see an insert bearing in an engine that's being worked on. I recall stories of mechanics who 'came up' with engines having babbitted and shimmed bearings seeing insert bearings and being in some disbelief about them. I know full well that my own experience with powerplant, steam, and diesel engine babbitted bearings is well beyond an 'apples and oranges' comparison to what you are working on. I do find it interesting that an old engine design's bearings could be 'tightened up' to give a longer service life.
 








 
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