Are you sure your M10 tap has 1mm pitch? Normal (coarse) M10 has 1.5mm pitch (about 17tpi ) and normal M5 has 0.8mm pitch (about 32tpi). M10x1 is possible - but considered "fine pitch". M5x1 will be some sort "special - extra coarse" (or "we did'it to make sure you cannot buy third party spares" )
See Threads - Metric ISO 724 for reference