[PROJECT] New to me "Ferro" Bridgeport clone mill.

[johnnyc14]

The Y axis lead screw and bronze nuts were completely worn out. I found out later that many Taiwanese mills use this same weird size threaded shaft for the screw. It is 32mm diameter but has 5 TPI acme threads, not the metric trapezoidal thread you would expect on metric sized shaft. The nuts are available for a reasonable price but not the screw. I wound up buying a 3 foot length of 1.25” acme threaded shaft locally and ordering 2 left hand thread nuts from Roton Industries, who were, by the way, great to deal with. The nuts were not the correct dimensions on the OD but were the correct 1.25” left hand acme thread to fit the shaft I bought. Since 32mm = 1.259” this seemed a good way to convert the shaft to a standard size. When the new nuts came I machined them to fit the mill’s feed nut bracket. I then machined the new screw shaft to match the original shaft’s dimensions and milled the keyway slots. I bought new RH thread 32mm nuts for the X axis from Supra Machine Tools on eBay. They were nearly a straight drop in part with only the bolt hole spacing needing to be modified.
 

 

 
This picture shows the newly machined Roton nut, then the nut as it arrived from Roton and the original nut.
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
 

 

 
I polished the threads with 600 grit paper after all the machine work was done.
 







 

 

 

 

 



The cross slide and table move super smoothly with very little backlash and I'm very pleased with how well it turned out.

 
To be continued.
 
John