Machinery maintenance

The locking sewing machine previously repaired lost it's function again yesterday, a failure in the mechanism of daring thread. Three needles play together well as a basic function, one of needles lost stability. The machinery user was about to calling a professional machinery engineer to repair it or to replace into a new model after 18 years use. But found I it possible to fix the needle holder just by tightening 3mm small locking screw with Allen wrench. After doing that the old machine required an original performance better than before, because it has been used spreading dangers with loosened needle condition. We have saved about 20,000 yen expenses in total.
I myself have Old Singer sewing machines made in England to be maintained, so must I a true service engineer of sewing machine very soon. Full overhaul of mechanical movements in addition to driving motor maintenance would be performed. I need a desperate decision before entering the different field as usual.
Also, the working chair from my intimate friend must be done, because it had be untouched for tens of years and the air way and water way must be clogged requiring full overhauling including cutting and grinding equipments. Basic lifting and lay down oil pressurized mechanism had been maintained already. DIY maintenance works are waiting for my ultimate efforts endlessly.