The sides and bottom of the keyway should be surfaced true with the file. If a keyway is to be cut by hand through a bore, as in a pulley or gear-wheel bore, its width should be marked with a T-square. This head is also driven by a key which engages a keyway in the boring-bar. The rod end should be planed to thickness for the brasses and of equal thickness on each side of the keyway. The flat key is used where it is necessary to secure the wheel more firmly without weakening the shaft by cutting a keyway in it. A much more usual method, however, is to employ slotting or keyway drills.
 Igneous, metamorphic, and sedimentary are descriptive terms used to  classify types of rocks, not minerals su â¦ ch as diamond.     Diamond is accepted as a valid mineral by the International  Mineralogy Association.
Metamorphic rocks can form from either sedimentary or igneous rocks. The sedimentary particles from which a sedimentary rock is formed can be derived from a metamorphic, an igneous, or another sedimentary rock. All three rock types can be melted to form a magma. Thus, the cycle has continued over the ages, constantly forming new rocks, breaking those down in various ways, and forming still younger rocks. Rocks at the surface of the earth range in age from over three billion years old to a few hundred years old.