Using machines to tan klaf
All stages of the processing from the lime bath onward must be done lishma. Some poskim hold that if the initial stages were performed lishma, all subsequent stages are considered lishma. Accordingly, if one stage was done lishma, whatever stages come after it can be performed by machine if the machine is started lishma. Other poskim permit machines if all the significant parts of the process are performed lishma. It is best for the entire process to be performed by Jews operating lishma.
(ס"ק ל, וביה"ל ד"ה להרמב"ם; ביאורים ומוספים דרשו, 50)