6 M12 are cloth, I can understand, but that attack 23 drill 24 what mean, according to reason, should be attack 23 drill 21, right?
This should be M12 thread depth, drilling depth of 24mm, tapping depth of 23mm.
The 23 attack drill 24 means with drill out the light hole cylindrical surface depth of 24mm, and then use the screw thread tapping into the effective depth of 23mm, which uses standard gauge M12 can be screwed into the 23mm, however, it should be marked drawings of consultations, the final hole should have 1.5 to 2 times the pitch pitch (M12 is 1.75), is about 3mm of the margin, or even the best teacher is also very difficult to achieve. This is my old fashioned experience for reference.
The 6 holes of M12 are evenly distributed on one flange, the drilling depth of the screw hole is 24mm, and the depth of the wire tapping is 23mm.
