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Thread: babbit removal
08-18-2003, 06:27 PM #1
I've got this old 'blacksmith' style belt driven Silver Manufacturing drill press, probably from the 20's. The motor turns a pulley and shaft at the bottom rear of the machine before transfering the rotation up to the top shaft of the drill press. The pulley and shaft arrangement bolted to the tail of the machine's bottom plate, has a short shaft suspended on babbet bearings. They are heavily worn and I want to replace them with probably bronze bushings, I'm totally unfamiliar with pouring babbit. I'm hoping after I get the babbit out, the insides of the bearing bosses will be machined smooth - maybe not, but my question is what is the best way to get the babbit out? Melt it with a torch or some other way???
08-18-2003, 09:58 PM #2
Assuming your machine is cast iron otherwise, a torch should melt out the babbitt, but be careful of it spattering. Handling it when it melts out is the trick, and that can be dangerous if you're not careful and know something about what you're trying to do.
Water and hot babbitt metal don't mix! Don't cool any parts in water if there's the least bit of babbitt present.
Read up on it before doing anything potentially dangerous. Babbitt was probably one of the most interesting inventions of early mechanical days, but I can understand wanting to replace it with something more modern.
08-18-2003, 11:28 PM #3
Ditto on the babbitt precautions above.
Unless you know someone that has a few ounces to give you, buying the minimum amount from venders will last you 1,000 years for that machine.
Go ahead and melt it out. There's probably holes or dimples where the babbitt meets the case. These keep the babbitt in place. If the case is cast iron, you might be able to chip it out. If it's steel, you'll HAVE to melt it out and clean the area of remaining zinc and babbitt.
Use a 660 bronze for the new bushing.
08-19-2003, 09:05 AM #4
Thanks guys, appreciate the info. After I wrote the questions, I found something on pouring babbit on metalwebnews that was also helpful. Yeah, this machine is cast iron. I hope after I melt this stuff out, the inside bores are smooth enough for a bushing, I hope if it has dimples they don't stick out in the way of a bushing. If it is dimpled, looks like I'll learn something about pouring babbit, doesn't it !. The shaft O.D. is about 1.186, what do you think for a running clearance ?
08-19-2003, 06:31 PM #5
Not that long ago we had a number of woodworking machines that needed new babbit once in a while and we had a local guy who did nothing but rebabbiting come in and do it. You may look for someone like that. maybe ask at a local wood shop with older equipment or if there are any Amish around, they like stuff like that. I never paid much attention to it back then but remembered it over heating and running out on the floor! Also we would replace with bushings when ever possible.
08-19-2003, 09:33 PM #6
Larry, those old timer manufacturers most likely cast the babbit in as-cast cored bores. The babbit was cast on a mandrel jigged from a reference and after cooling the babbittedpart was sent on to reaming or boring operation.
One of the best kept secrets for strongly bonded babbitt is to thoroughly tin the cavity to be babbitted with pure tin scrubbing it in with a wire brush and plenty of killed HCl/ZnCl flux. The right preheat of the housing is important too. You don't want the babbitt to chill before it bonds with the tin.
A favorite clearance/release agent is to soot up the mandrel from an acetylene flame. The babbitt will shrink around the mandrel and hold it tightly but the soot will prevent it from bonding and add a little clearance.
Babbitting can be tricky. Don't be embarassed if things go wrong and you have to babbitt the part all over again.
Naturally, I NEVER screwed up any of the babbitt bearings I poured. Nope. Not me.
Ever see how far 80 lb of molten babbitt flies when centrifugally casting a 22" dia line shaft bearing in an engine lathe and a fire clay plug blows out?
08-19-2003, 11:07 PM #7
Larry,the babbit in your drill probabably lasted longer than bushings would of. The old babbit can be reused. I made a shaft for an old8ft.dia.windmill then melted the old babbit out.Used one wrap of light weight brown paper around the shaft,centered it in the casting,used asbestos rope around each end to plug the opening and poured the molten babbit through the oiler hole,very carefully!! When everything was cool,the shaft pressed out easily.There were some voids,but my old neighbor said they would hold lube,forget them. It is still in operation as of last year.Poured the babbit in 1965.
08-19-2003, 11:28 PM #8Millwrong Guest
Larry, if there is a Ford Model A club in your area they might have everything you need including advise. Our local Model A club recently bought babit pouring and boring equipment. There's a national Model A club also, I think it's called MAFTA or something like that.
08-19-2003, 11:43 PM #9
Thanks guys, yeah, I've read the article on pouring babbet on metalwebnew, I'm sure there's more reading to research. I have not quite figured out what babbitrite is yet, but it'll come to me. Evidently they use collars to hold a given diameter shaft in place along the centerline of the shaft, seal the ends of the bearing bosses, pour the molten babbit in thru the oil hole. Now that's a mighty small hole, maybe 1/4 or 5/16's inch. They soot up the shaft for a release agent. Evidently the collars are lipped to locate themselves in the bosses, otherwise I don't know how they would find the centerline.Seems that kit is rentable.I don't know, if a bushing would work, thats the way to go. Might be fun to try the babbiting process.
08-21-2003, 12:16 AM #10
I just did a lower babbit bearing replacement on my Silver drill press. It came from a 100 year old shop and looked as if it had not been oiled in at least 30 years, the shaft was so worn that it had to be replaced also. I held the new shaft in place in the cast iron bearing support in a vertical direction with a temporary wooden fixture with a pair of wood blocks clamped around the shaft at the bottom of each support to keep the babbit from running out, and put a turn of typing paper held onto the shaft with sticky ball bearing grease to provide running clearance. You will need to seal around the edges of the bearing supports where the blocks are clamped to keep the babbit from running out, there are compounds made for this but I made my own by mixing 1 part Western bentonite clay with 3 parts fire clay and just enough glycerin to form a bread dough-like putty. Be sure to seal the oil holes too. I melted out the old babbit with a torch into a ladle for re-use, it's melting temperature is not much higher than soft lead based solder. The bearing supports on mine are fairly rough on the inside, but each has a retaining lip at each end to lock the babbit in place.
08-21-2003, 01:49 AM #11
Thank you Mike, especially the info about the finish inside the bearing supports or what I call the bearing bosses. It's good to hear from someone who has one of the old Silver drill presses as well. I'm taking a couple days off starting tomorrow, so I hope sometime in the next 4 days of 'honey do's', I can melt out the babbit on mine and check the bores out for myself. Looks more and more I'm re-babbiting this thing instead of bushings. That's cool, I'll learn something new. I have to buy a latle (sp) and figure out how to melt the babbit. I've got an old Japanese iron pot I betcha I could get hot enough with charcoal to melt new stuff. I'll have to do some more reading and asking.
08-21-2003, 02:54 AM #12
It's not wise to reuse babbitt. (Although I have heard you can add 50% new and get by). Every time it's melted (overheated to melt out), it burns up (oxydizes) some of the tin and antimony. This can make the babbitt too brittle. If it's a lead based babbitt ("Genuine" - but not the best), it can make it too soft.
I have about 3-4ozs. of ASTM-B23-3 leftover from a job. If that's enough to do your bearing, your welcome to it.
Forgot to mention-- Running clearance on a shaft that size should be about .002". That means .001 on each side of the shaft. (.002 total). Also, there should be some provision for OIL. Either a cup or a flip-top with a wick. Don't use anything heavier than 30w. In fact, a 20w would be better. Oil before each use.
[This message has been edited by CCWKen (edited 08-21-2003).]
08-22-2003, 05:33 PM #13
Hmm, I just miked the typing paper I used and it's .004" thick, so if the clearance is supposed to be .002" I may have a problem. This is the first time I have poured a babbit bearing and the paper idea came from an article in a back issue of Fine Woodworking about restoring old machines. Oh well, I guess I will just have to wait and see how it holds up. Using some kind of covered oil cup is a good idea and I added a set on both the top & bottom shafts on mine, they just drilled an open hole over each bearing at the factory and the holes were almost completely blocked with dirt when I got the machine.
08-22-2003, 05:43 PM #14
You guy thinking to use typingpaper to keep clearance for a babbitt bearing better think again. Tin babbitt is poured about 900 degrees. Ordinary paper will scorch and curl at that temperature. Besides it's too thick as was pointed out earlier.
Better to soot up the chaft (or mandrel) and scrape the bearing for fit and clearance. There's inevitably a bit of surface dross to be removed anyway.
08-22-2003, 06:21 PM #15
is that "Schmorange" soot or regular?
08-24-2003, 04:11 PM #16
Larry and the Rest of You --
The current (Spring, 2003) issue of the on-line magazine Vintage Windmills (www.vintagewindmills.com) contains an article titled "602 Babbitt Pour" that is well worth a look-see.
The author doesn't claim to be a babbiting expert -- in fact, he specifically warns that he is only describing how he actually performed one particular job, not describing any generally-recognized-as-proper technique -- but I'd say that in combination with the information on this "thread" of postings it's possible to develop a good mental image of the babbiting process.
An old "rule of thumb" for journal-bearing running clearance is to allow a diametric clearance of 0.001 inch per inch of shaft diameter for an oil-lubed bearing or 0.002 inch per inch of shaft diameter for a grease-lubed bearing.
As Forrest indicates, it's fairly standard practice to "soot" the shaft with acetylene smoke to keep the babbit from bonding to the shaft, but lack of an acetylene flame doesn't stop the parade. Similar results can be had by smoking the shaft with a candle flame or the flame from a kerosene lamp, and I remember watching an old-time oilfied mechanic coat a shaft with daubed-on silt from the bottom of a mud puddle.
Finally, the fluid babbit must be captured between the shaft and the body of the journal long enough for the babbit itself to freeze. This requires filling the spaces through which the fluid babbit could flow, and is often termed "damming". Babbit dams are often solid, but don't often fit the shaft and journal housing well enough to be fluid tight, so a gasket of some sort is necessary. The gasket may be a literal gasket, made of a refractory sheet material, or may take the form of a rope seal or a putty. Babbit Rite is a commercial babbit-damming compound, and Duxseal has often been used for this same purpose. KyMike mentions using a homemade clay-and-glycerine putty, others have used clay-and-oil putties, and the same old guy who used silt as a release agent used what he called "cookie dough", a putty mixed from flour and molasses.
08-24-2003, 05:27 PM #17genekeller Guest
If you don't want to try it yourself, try an electric motor rewinder. I recently visited a large commercial motor rewind shop and they had a complete rebabbiting service available, as a lot of elctric motors use babbit bearings. They told me they could renew babbit bearings for me. I have no idea as to cost, as each job would be priced according to the time and material needs.
08-24-2003, 05:30 PM #18
Thank you very much for that information John, and all the rest of you all as well. Looks like I'm gonna have a chance to learn "all about" pouring babbit in the near future. I'm going to round up the babbit material and babbitrite, got to buy me a ladle. I'm thinking I can melt the stock on a charcoal fire in an iron pot. Thinking I'm gonna mount the new shaft vertically in the casting, center the shaft probably with something I make on the lathe clamped to the bottom side of each boss, complete with countersunks to hold the babbitrite surrounding the centered shaft and around the outer edges, then just fill up both bosses fron the top with poured babbit. That seems to be the best way, ought to work. It says so right here in the script.
08-24-2003, 11:07 PM #19Fred P Guest
My Dad was a foundry worker most of his life. I watch and helped him pore several babbet bearing. He would rap the shaft with wax paper. Remember the babbet will shrink when it cools. Soot will give you near 0 clearance for oil. It will work, but it is not wrong to have a little room for lub. I have mested up more things by having to little clearance than I have by having to much clearance.
08-24-2003, 11:23 PM #20
Yeah well the soot acts as a parting agent but it doen't give you any clearance. If you use the shaft for the mandrel you still have to add clearance. This is why you blue up the shaft so you can scrape in the bearing. By the time you've scraped the parting dross and the soot out of the babbitt you'll be on the way to fitting the shaft to the bearing. After you get to clean sound babbitt you shim the caps to secure the proper clearance.
For bushing style (non-separable) babbitt bearings you have to scrape it the hard way. This can be tricky work but it's do-able - in fact it was purgatory for the apprentices who ccommitted the petty crimes of sitting down when doing anything at all onthe shop floor, being late with your log book, failure to keep your machine and work area clean and organized, et-effing-cetra way back when.
Casting the bearing is only the first part of a re-babbitting job. Fitting it to the shaft, detailing the oil pockets, clearing drain back grooves, and thorough cleaning is the other 65%.
[This message has been edited by Forrest Addy (edited 08-25-2003).]