Probably an in/mm conversion problem. STL files don't have any units embedded within them so it's us to the user to specify. If MeshCAM is telling you 76x101 then Solidworks is exporting in mm one way or another. MeshCAM doesn't do any multiplication on import- what you see is what the cad software gave you. As a backup you can import as in then scale the model by 1/25.4 .