A blind hole is better tapped with a tap having

Find the speed range ratio for the drilling machine spindle if the minimum and maximum diameters of drills used are $$5$$ $$mm$$ and $$25$$ $$mm$$ respectively and if the machinability indices for the work materials are $$120$$ (brass) and $$40$$ (alloy steel)

If the index crank of a dividing head is turned through one complete revoluation and $$10$$ holes in a $$30$$ hole circle plate, the work piece turns through (in degrees)

In a grinding wheel marked with $$AA-48-L-7-V-25, L$$ refers to