Which abrasive is used for soft ferrous and non-ferrous metals for lapping?

Explanation:

Lapping abrasives:

Abrasives of different types are used for lapping. The commonly used abrasives are:

Silicon Carbide

• This is an extremely hard abrasive.
• Its grit is sharp and brittle.
• While lapping, the sharp cutting edges continuously break down exposing new cutting edges.
• Due to this reason this is considered as very ideal for lapping hardened steel and cast iron, particularly where heavy stock removal is required.

Aluminium Oxide:

• Aluminium oxide is sharp and tougher than silicon carbide.
• Aluminium oxide is used in un-fused and fused forms.
• Un-fused alumina (aluminium oxide) removes stock effectively and can obtain high-quality finish.
• Fused alumina is used for lapping soft steels and ferrous metals.

Boron Carbide

• This is an expensive abrasive material which is next to diamond in hardness.
• It has excellent cutting properties. Because of the high cost, it is used only in specialised application like dies and gauges.

Diamond: 

• This being the hardest of all materials, it is used for lapping tungsten carbide.
• Rotary diamond laps are also prepared for accurately finishing very small holes which cannot be ground.