Smoothing and finishing stainless to a "mirror shine"

Discussion in 'Metal Boat Building' started by westsail42, Mar 8, 2008.

  1. westsail42
    Joined: Mar 2005
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    westsail42 Junior Member

    For you metal workers out there...

    When you are done shaping and fabricating stainless parts, how to you sand/grind out scratches and polish the surface to a "mirror shine"?

    Is it like varnishing wood where you use progressively finer grits? Then finish off with a polish?

    I need to do this with a stainless part and have never done it before.

    thanks!
     
  2. pescaloco
    Joined: Feb 2006
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    pescaloco Senior Member

    stainless

    depends on the shape of the parts, but in general 80 grit paper mabee on a D/A sander if it is flat / then 150 paper / scotch bright pads (fine) on hand held or bench grinder / green rousche and a cotton buffing wheel.

    that shoud give you a nice polished finish, they also electro polish stainless.

    Not an expert but it works for me

    mark
     
  3. alan white
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    alan white Senior Member

    I have used 3M (scotchbrite) pads on a hand-held grinder. They require a special rubber disc with a 5/8" threaded arbor, available where the discs are sold. The system has several disc grits, which take over where sanding discs leave off (maybe 180 grit). They have a plastic threaded stud on the back that screws into a threaded hole on the face of the disc. They're very fast to change, requiring a quick twist counterclockwise.
    After reaching the highest polish you can get with the 3M discs, you can machine buff using progressive compounds that go up into the thousands.
    Using these progressive methods will ensure no deep scratches appear later.
    Small parts can be done on a bench machine.

    Alan
     
  4. SaltOntheBrain
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    SaltOntheBrain Senior Member

    I agree fully with what Alan White said.

    Sometimes scotchbrite discs can be hard to find, though. I made my own out of scotchbrite pads. Cut discs out of a pad (the black one made for stainless) and use a piece of sharpened 7/8" S/S tubing to punch your arbor hole.

    They work best on a Challenger disc nut and backer. Sait/United Abrasives makes the Challenger discs and they use a special nut and flexible cupped backer. They work well because they cup the pad enough that it can be used flat and the nut won't touch.(You mught need to double-stack the pads, though)

    They also make cotton buffing wheels that work on small angle grinders, so you don't need a bunch of different tools. You'll be surprised how fast you can get the finish you're looking for with just a grinder and a handful of stuff for it.

    Lance.
     
  5. westsail42
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    westsail42 Junior Member

    Thanks for the tips guys. My vendor supplies Scotchbrite conditioning pad from coarse to very fine, in 2 inch diameters (this is a small part). Price is pretty reasonable (86 cents per pad). It uses the Roloc system that I think Alan was describing. They also sell adaptors to a power drill and are pretty inexpensive to (the part in question is already installed).


    I will give that a try.

    Thanks again.
     

  6. alan white
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    alan white Senior Member

    That's right, it's Roloc. I use the 3" size. The speed at which you can change grits is amazing.
     
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