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  I use different tunings very often and this construction did not work properly. I remembered to have an easy-tuning classic guitar with Rubner machines and they are equipped with ball bearings!! |  
  These ball bearings are surprisingly cheap and very effective. |  
  It takes some courage to work with this drill on the guitar if you have to work free-hand. |  
  The inside 6 and outside 10 mm ball bearings fit exactly the axles of the Schaller machines. | 
 
  The first attempt for a slide bushing. I made at least 4 different ones but they all did not work well. I must build a better one before I go to work on my 12strings.. |  
  Yoe need a slide bushing because the dril will "dance" in the hole without it. I later used another one which was much longer. |  
  The first drilling hole gave me the courage to try the rest. |  
  On the first attempt I forgot to fill the drilling hole in order to give the drill a center but fortunaltely it worked well. | 
 
  Looks nice, nearly invisible. |  
  Completed. Works perfectly. |   |   | 
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