US Patent: 255,725 
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| Hardening metals
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	        Patentee:
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 | Charles M. Daboll (exact or similar names) - New London, CT |  
 
 
 
 
 
| Manufacturer: |  
| Not known to have been produced |  
 
 
 
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        Patent Dates:
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| Applied: | 
Aug. 25, 1881 | 
 
| Granted: | 
Mar. 28, 1882 | 
 
 
 
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                        Jeff Joslin Vintage Machinery entry for Wilson Mfg. Co. (CT) 
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        Description: |  
| The inventor is known to have worked for I. Wilson of New London, which became Wilson Mfg. Co.This patent is a companion to patent 255,724 for a roller-bearing pulley for use on ships. This patent provides a recipe for hardening the cast iron components: a bath of 40 gallons water, 50 lb salt, 2 lb saltpeter, 5 lbs potassium cyanide, 5 lb sulphuric acid. The parts are heated first but no hints are provided as to how hot. |  
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