Locking sewing machine

Locking sewing machine lost it's function last night, so I was a service man for repairing it taking time 30 minutes costing free of charge, because I did by myself. Closed tight string guide, one of three, was the reason of disorder, in order to under stand the fundamental function of the guiding way of a string, disassembling some parts was required. Air pressure by manual function to activate equipped air pump was supplied into guiding pipe, but any clogged material in the way prevented to go into the pipe way. After some consideration, connecting silicon tube at the exit nozzle and human respiratory negative pressure and the positive one with pomp could made it possible to flow through some chronic material, small piece of string inside of the pipe on the way. The use has been made it a rule to connect by binding old and new string being afraid to miss the tip of the string. This kind of bad habit was the reason for dysfunction. As an additional maintenance, lubrication on moving parts was done before assembling.