Quote Originally Posted by wdrzal View Post
turn the bottle upside down when taping, you can get away without using oil on soft metals like copper,brass aluminium,even mild steel as long as the tap size is small enough . Plus take its slow and keep reversing the tap to cut off the shavings. when to reverse depends on number of flutes on tap.

oil is always prefered,but tapping can be done without it. some metals used in aircraft that are cnc milled with no oil or solvent as in would dammage the metal.
You can also fill the flutes with a bearing grease to catch the shavings.