When choosing a stone to begin polishing a mold or die there are many factors that must be considered. A few of the most common are listed below:
a. Mold Material
- Steel (P20, Stainless Steel, H13, D2)
- Non Ferrous (Aluminum, Bronze)
b. Material Hardness
c. Finish quality left by the machining process
d. Shape of mold surface
- Rib or Slot
- Detail area
e. Desired final finish
In general, it is always better to start with a finer stone. If a coarser stone is needed, you can always go coarser to achieve the best result.
In most cases, you can start with a 220 grit stone for conventional machined surfaces. EDM surfaces may require a coarser grit stone to remove the hard re-cast layer.
For ground surfaces, a finer stone can be used to start the polishing process.
For radius surfaces, it is good to use a softer stone that will take the shape of the mold.
For detail areas that require a mold feature to be maintained, it is better to use a harder stone that will keep its shape.
Always use a lubricant with harder stones to prevent stone loading.