Sewing machine tools
The most important tools for sewing machine repair starts with long screw drivers(12")are best, one narrow small blade, one medium size blade, and one large thick bladed. The medium blade will be used most the large not so much but never use them for anything but sewing machine repair. All screws on these machine require high torq and the trick with long drivers is that the screw driver shaft will twist part way before the screw will break from the seat to losen and the opposite is true when tightening the screw to it's seat. On all size screws your angle of attack must be exact or stripping the slot of the screw will happen every time(that then really sucks).
Other tools required :
Heavy duty twezers,,small bright flash light,,Allen wrench set(again not rounded tips)every size you ever imagined,,small narrow angled open ended wrenches(like distributor repair set),,flat basterd files(asually small and medium size),,pencil magnet(all screws grow legs and hide),,good quality crescent wrenches 1four inch,1ten or twelve inch,,and most important a couple sizes of rope files both round and flat(most sewing supple, repair places carry) there are some things that don't come to mind at the moment but a tool that is hard to describe is a sewing needle shaft adjustment tool that is a feeler gauge set(don't have it in front of me but it has 4 or 5 horse shoe shaped gauges)used to set needle timing to sewing hook, without it you can guess and be off by miles.
The rope files are also your best friend to debure parts such as the needle plate hole,,sewing hook,,etc. A lot of sewing problem stem from burrs that are responsible for thread breakage. But file carefully a too big needle hole is like,,,,use your imagination.
My experience repairing sewing machines was no walk in the park, there are timing and cams in sewing machines that make car motors look simple but time and patience always works wonders. Enjoy the challenge