Stoning Basics

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

· Soft

· Hard

· Heat Treated

c. Finish quality left by the machining process

· EDM

· Milling

· Grinding

d. Shape of mold surface

· Flat

· Radius

· 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.

By Allan Diaz
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