Cleaning the blade of a old square
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  1. #1
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    What would be the best (and least destructive) method for cleaning the dark oxidation (discoloration, patina?) from the blade of a combination square. I recently bought an old Tumico square and the blade while readable is dark. In addition the square and protractor heads also have some spots on the machined surfaces. How should I clean these up without ruining the machined surfaces? My machinest neighbor once showed me how hydrochloric brightened up to very old scales, but I hesitate to do this.

  2. #2
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    What would be the best (and least destructive) method for cleaning the dark oxidation (discoloration, patina?) from the blade of a combination square. I recently bought an old Tumico square and the blade while readable is dark. In addition the square and protractor heads also have some spots on the machined surfaces. How should I clean these up without ruining the machined surfaces? My machinest neighbor once showed me how hydrochloric brightened up to very old scales, but I hesitate to do this.

  3. #3
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    Scotch-Brite and WD-40. Done it numerous times. While it won't make it look brand new, it will surely be a great improvement.
    Greg B.

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    Scotch-Brite and WD-40. Done it numerous times. While it won't make it look brand new, it will surely be a great improvement.
    Greg B.

  5. #5
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    It's a little risky using harsh methods when cleaning a scale with graduations on it. It's easy to blur the crisp edges that make the graduations easy to read. for that reason I strongly reccommend against any conformal like abrasive paper, ScotchBrite, or even wet or dry applied to a flat block. I learned this the hard way trying to restore an heirloom combination set for one of my apprentices. It was readable but the edges were rounded over.

    Since then I've cleaned up rusty smutty scales and verniers using a slip stone held flat tot eh surface with a kitchen spray cleaner to keep the swarf in suspension. I went to bright metal taking off 0.002" in some cases and still had clear sharp graduations.

  6. #6
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    It's a little risky using harsh methods when cleaning a scale with graduations on it. It's easy to blur the crisp edges that make the graduations easy to read. for that reason I strongly reccommend against any conformal like abrasive paper, ScotchBrite, or even wet or dry applied to a flat block. I learned this the hard way trying to restore an heirloom combination set for one of my apprentices. It was readable but the edges were rounded over.

    Since then I've cleaned up rusty smutty scales and verniers using a slip stone held flat tot eh surface with a kitchen spray cleaner to keep the swarf in suspension. I went to bright metal taking off 0.002" in some cases and still had clear sharp graduations.

  7. #7
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    might try a mild phosphoric acid bath. coke/pepsi/rc/drpepper
    overnight would be a start, longer if needed.

  8. #8
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    might try a mild phosphoric acid bath. coke/pepsi/rc/drpepper
    overnight would be a start, longer if needed.

  9. #9
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    Oil and fine steel wool. Will not bring it up as broght as Forrest Addy's method but will inprove readibility.

    Jim C.

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    Oil and fine steel wool. Will not bring it up as broght as Forrest Addy's method but will inprove readibility.

    Jim C.

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    I lik a product called sand-flex- it's an abrasive suspended in a rubber block available from klingspor- literally a rust eraser. Because the abrasive goes all the way through you can profile it to get into tight spots. I think it available elsewhere- I haven't looked- here's the link I know.

    Sand flex

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    I lik a product called sand-flex- it's an abrasive suspended in a rubber block available from klingspor- literally a rust eraser. Because the abrasive goes all the way through you can profile it to get into tight spots. I think it available elsewhere- I haven't looked- here's the link I know.

    Sand flex

  13. #13
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    Forest, I am a little confused by all the conflicting replies to my question. You are saying any type of chemical method might make the graduations less readable. Correct? So skip the HCL dip and no Coke or Pepsi. Don't use Scotchbrite or steel wool, because I will loose flatness and round the edge of the rule. You advocate gently stoning the surface. Would a very fine grit Japanese waterstone be okay?

  14. #14
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    Forest, I am a little confused by all the conflicting replies to my question. You are saying any type of chemical method might make the graduations less readable. Correct? So skip the HCL dip and no Coke or Pepsi. Don't use Scotchbrite or steel wool, because I will loose flatness and round the edge of the rule. You advocate gently stoning the surface. Would a very fine grit Japanese waterstone be okay?

  15. #15
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    Reggie, I'll concur with Forrest on this one......I've polished our a few old scales, one time and another, and found, exactly as did Forrest, that anything other than a very fine oilstone will radius the sharp edges, and create minor irregularities in the flat surfaces.

    A fine Japanese waterstone is probably still too coarse for this purpose. A "Lily White Washita", or equivalent, used with a very light oil, such as "Break-Free" or equivalent, or mil-spec gun oil, or even "WD-40", or kerosene, if you've nothing better, will give you the best chance to clean up your scale nicely.

    cheers

    Carla

  16. #16
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    Reggie, I'll concur with Forrest on this one......I've polished our a few old scales, one time and another, and found, exactly as did Forrest, that anything other than a very fine oilstone will radius the sharp edges, and create minor irregularities in the flat surfaces.

    A fine Japanese waterstone is probably still too coarse for this purpose. A "Lily White Washita", or equivalent, used with a very light oil, such as "Break-Free" or equivalent, or mil-spec gun oil, or even "WD-40", or kerosene, if you've nothing better, will give you the best chance to clean up your scale nicely.

    cheers

    Carla


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