adjusting bolt 611 extends through the adjusting hole 610 and contacts the action end 513 the control arm 28 includes a contact end 282 at one end thereof and the other end of the control arm 28 has a pushing end 281 the contact end 282 is located close to the tension adjusting frame 30 and the pushing end 281 is engaged with the travel control portion 270 of the control wheel 27 as shown in fig4 to 6 when restoring the sewing machine 10 it is regardless to the positions of the restoring rods 421 of the micro adjusting sets 40 when the adjusting knob 23 is rotated the restoring arm 62 is driven by the rod 620 of the control set 60 which is activated by the restoring disk 241 the restoring arm 62 applies a force on the pressing board 61 the restoring arm 62 moves back to its initial position by the end piece 29 the restoring disk 241 is driven by the active member 24 and the passive member 25 and activates the driving member 65 on the other end of the control shaft 26 the driving member 65 drives the rod 641 the function end 640 and the pushing end 630 to apply a force to the connection boards.