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Casting (Babbitt) putty question

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  • challenger
    replied
    As I said, my plan to coat the lead screw with Babbitt was based on the recommendation from another member. I don't know enough about the process or application to make judgements about the feasibility. Obviously most feel it's a bad idea. I feel like I won't be able to add Babbitt to the inside of the nut evenly. For these two reasons I'm abandoning the Babbitt idea.
    I have modified lead screw nuts before by slitting and spreading or compressing them. I will do the same on this mill I suspect. Both the screw and the nut are worn so fixing one won't fix the backlash problem but should improve it. I have no problem dealing with backlash however I have the mill apart and figured I'd try to address the backlash.
    Fwiw the screw is .875" RH and about 3' long with the usual ends having larger diameter features. I may look around for a replacement screw and nut to explore the option of replacing both with new.
    Thanks

    Sent from my Pixel 2 using Tapatalk

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  • elf
    replied
    Originally posted by Illinoyance View Post
    Geez. The guy was asking about what type of putty to use for a dam. He did not ask for a course in Babbitting bearings or did not ask to have his method attacked.

    Years ago I used plumbers putty as a dam when pouring a new bearing for my Little Giant hammer. It worked.

    Hmmm. When is a bearing the same as a leadscrew?

    Leave a comment:


  • CreakyOne
    replied
    Originally posted by CreakyOne View Post
    I don't picture the exact setup, but it sounds to me as if you want to anchor the nut in the babbit and use the putty to contain the metal on the sides. Does the nut fit into a casting pocket?

    Most babbit alloys have a relatively low melting/pouring point so you may be able to use a number of tricks. First, you can make your own putty using dry, finely ground ceramics clay (which is cheap and probably available near you) mixed with an oil. Window glass-setting putty used linseed oil; silicone oils might be best, but even vegetable (e.g. soy) or motor oil would work in a pinch. All but the silicone might cause some smoking.

    Another material which can be used, if supported by wire, rods or if plugging holes, is waded aluminum foil. Sometimes foil is good to use as a boundary layer (multiple slightly-crumpled layers can provide insulation) over homemade oil putty or Plaster of Paris, the last material. Plaster works well where large areas need to be covered and the section can be removed, dried somewhat, then reinserted. If it shrinks too much during the drying, shimming with aluminum wadding can make it fit well.

    As with any procedure, care needs to be used. Water or oils can create pressure when heated and the putty or plaster have them, so consider those factors when designing your 'system'.
    Originally posted by Illinoyance View Post
    Geez. The guy was asking about what type of putty to use for a dam. He did not ask for a course in Babbitting bearings or did not ask to have his method attacked.

    Years ago I used plumbers putty as a dam when pouring a new bearing for my Little Giant hammer. It worked.
    I didn't read Challenger's first post very well (no excuse, either!), or I wouldn't have given the response I did. I would have realized what he was trying to do was both difficult and a poor substitute for better and easier methods. If I were in his position and didn't know the problems with my idea, I would appreciate being told. Yes, on occasion I have chosen to do things the dumb, difficult or even supposedly impossible way, either out of curiosity, stubbornness, or to prove a point...but I knew what I was getting into. Now he does too.

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  • Illinoyance
    replied
    Geez. The guy was asking about what type of putty to use for a dam. He did not ask for a course in Babbitting bearings or did not ask to have his method attacked.

    Years ago I used plumbers putty as a dam when pouring a new bearing for my Little Giant hammer. It worked.

    Leave a comment:


  • 754
    replied
    It not that hard to make a tool and cut Acme thread in bronze..
    Unless it's under 9/16 screw size, then the homemade tools are tougher to make ridgid enough.

    Leave a comment:


  • elf
    replied
    http://bbs.homeshopmachinist.net/thr...s-the-easy-way

    Leave a comment:


  • Mark Rand
    replied
    Measure the feedscrew and nut, then turn a new nut out of phosphor bronze or cast iron. It isn't rocket surgery.

    Leave a comment:


  • 754
    replied
    How many weeks of use do you expect out of a Babbitt nut ?

    Leave a comment:


  • CCWKen
    replied
    Can you post a picture of the feed nut bracket and nuts? If your machine doesn't have backlash adjustments, perhaps they could be added. It would entail cutting the nuts in half then adding a screw that would either push the nuts apart or pull them together to remove backlash. You could probably accomplish this with a drill press since the mill is apart.

    Leave a comment:


  • challenger
    replied
    This is for a 1" lead screw and a brass nut from an early 40s index mill table. Screw and nut are out of the machine. I have it apart and I'm cleaning it for paint. My thought, as suggested by a member here, was to drill a hole in the nut and pour Babbitt into the hole so that it fills in the worn areas of the nut. Now, after thinking about it I'm inclined to think this won't work because the screw and nut will be touching on one side. Never mind. I'll try to find another way to remove some of the backlash.

    Sent from my Pixel 2 using Tapatalk

    Leave a comment:


  • CreakyOne
    replied
    I don't picture the exact setup, but it sounds to me as if you want to anchor the nut in the babbit and use the putty to contain the metal on the sides. Does the nut fit into a casting pocket?

    Most babbit alloys have a relatively low melting/pouring point so you may be able to use a number of tricks. First, you can make your own putty using dry, finely ground ceramics clay (which is cheap and probably available near you) mixed with an oil. Window glass-setting putty used linseed oil; silicone oils might be best, but even vegetable (e.g. soy) or motor oil would work in a pinch. All but the silicone might cause some smoking.

    Another material which can be used, if supported by wire, rods or if plugging holes, is waded aluminum foil. Sometimes foil is good to use as a boundary layer (multiple slightly-crumpled layers can provide insulation) over homemade oil putty or Plaster of Paris, the last material. Plaster works well where large areas need to be covered and the section can be removed, dried somewhat, then reinserted. If it shrinks too much during the drying, shimming with aluminum wadding can make it fit well.

    As with any procedure, care needs to be used. Water or oils can create pressure when heated and the putty or plaster have them, so consider those factors when designing your 'system'.

    Leave a comment:


  • JRouche
    replied
    Originally posted by CCWKen View Post
    There's many types of babbitt. Some contain no lead or only a trace amount. I've got about 30 pounds of "no-lead" babbitt
    Hell yes! I want that. Thats a pretty penny right there.

    And yes, I no nuthing about babbit bearings. I have heard that some old engines use a cast babbit bush. I want 30lbs!! JR

    Leave a comment:


  • CCWKen
    replied
    There's many types of babbitt. Some contain no lead or only a trace amount. I've got about 30 pounds of "no-lead" babbitt that I used in old engines.

    But, getting it to stick to a greasy, oily nut is a different story. The nut must be free of any oil or oxidation. Get some tinning fluid and a can of high temp mold release. This is usually a boron powder with a fast drying carrier. Spray a portion the clean lead screw and run it into the tinned bushing. The babbitt will need to be about 900*F for pouring. Some types vary on pour temp and it wouldn't hurt to preheat the nut. You'll need to make a dam from something that can handle the temp. Don't use anything containing water!

    An important setup to consider is alignment of the nut and screw if they are out of the machine. Not sure how you'd pour it in-place unless it's through an oil hole. That's where preheating would help to insure flow around the screw.

    Doesn't your mill have adjustable bushings?

    Added:
    Just thought of something. You could mix up a small portion of "green sand". Pack it around the joints and wrap with foil to hold in place. Or just use a few layers of foil.
    Last edited by CCWKen; 05-27-2018, 12:19 AM. Reason: Addition

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  • JRouche
    replied
    When I think of babbit I think of lead.

    I dont think you can coat the surface of a screw or nut and expect it to last, it might shear right off.

    Am I wrong to understand you want to use babbit on the screw mechanism? JR

    Leave a comment:


  • Gary Paine
    replied
    Why do you think the Babbitt would stick to the nut and not the screw?

    Leave a comment:

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