What is the purpose of polishing stone?

View Catalogue Here

For nearly 30 years CMP Stone has worked with talented Australian stonemasons, sculptors, restoration professionals, and other stone enthusiasts to manufacture world-class stone working tools in Australia.

Which Polishing Stone is Best for Which Application?

Which polishing stone you should use depends on the material of the mold you’re polishing, the shape of the mold surface, how you are polishing (wet or dry), and the desired final finish. See below for a detailed guide. Also check out our polishing stone application chart.

Breakdown is based on a scale of 0 to 5, where 0 is slow and 5 is fast.

Hardness is based on a scale of 0 to 5, where 0 is soft and 5 is hard. 

EDM Polishing Stones

AM-8 Polishing Stone

Aluminum oxide stone designed for removing EDM (electrical discharge machining) scale on all types of mold and die steel. AM-8 is the hardest stone that we manufacture. It holds its shape well and breaks down slowly. Particularly great for use on heat treated steels.  

• Available Grits: 100-1200

• Methods: Hand Polishing, Air Profiler, or Ultrasonic Polishing

• Materials: EDM surfaces and all types of mold and die steel, especially heat-treated steels

• Use: Wet only

• Breakdown: 2

• Hardness: 4

AS-9 Polishing Stone

AS-9 is our most popular EDM stone. It is an aluminum oxide stone engineered for hand stoning EDM scale surfaces as well as cutting and machining marks on all types of mold and die steels. It is a bit softer than the AM-8 offering faster breakdown and the ability to conform to the shape of the tool being polished. Provides a fast, smooth cutting action during hand stoning and flat lapping. Best used for hand polishing but can also be used in reciprocating profilers.

• Available Grits: 100-1200

• Methods: Hand Polishing or Air Profiler

• Materials: EDM surfaces and all types of mold and die steel

• Use: Wet or Dry

• Breakdown: 3

• Hardness: 3

AS-9 PLUS Polishing Stone

The AS-9 PLUS is an enhanced version of our popular AS-9 stone. It was engineered to produce the same fast, smooth cutting action you can expect from the AS-9, but with superior finishing capabilities. Manufactured using premium aluminum oxide grain, the special formulation of the AS-9 PLUS produces wider scratches on the mold surface which results in an overall smoother and more brilliant finish. Use the AS-9 PLUS on all types of tool steels and EDM (electrical discharge machining) scale surfaces. Best used for hand polishing but can also be used in reciprocating profilers.

• Available Grits: 320-800

• Methods: Hand Polishing or Air Profiler

• Materials: EDM surfaces and all types of tool steel

• Use: Wet or Dry

• Breakdown: 3

• Hardness: 3

Orange EDM Polishing Stone

Excellent for fast EDM scale removal. Breaks down faster than AS-9 making it great for molds with contours. Provides fast and consistent cutting action. Best used in a reciprocating profiler but also works well by hand.

• Available Grits: 120-600

• Methods: Air Profiler or Hand Polishing

• Materials: EDM surfaces and all types of tool steel

• Use: Wet or Dry

• Breakdown: 3

• Hardness: 3

Golden Star Polishing Stone

Offers superior breakdown characteristics, and a smooth, silky finish on EDM surfaces, and milling and machining marks. Contours quickly to the shape of the mold surface.

• Available Grits: 150-1000

• Methods: Hand Polishing or Air Profiler

• Materials: EDM surfaces and all types of tool steel

• Use: Wet only

• Breakdown: 4

• Hardness: 3

General Purpose Polishing Stones – Aluminum Oxide

AM-2 Polishing Stone

An excellent all-around finishing stone and the most popular of our general purpose line. Fast cutting and versatile polishing stone for general polishing on nearly any material. Quick breakdown allows the stones to conform to the shape of the mold.

• Available Grits: 100-1200

• Methods: Hand Polishing or Air Profiler

• Materials: All types of mold and die steel including P20, H13, S7, T-420, and SAE 1030 pre-heat treated, as well as aluminum and other non-ferrous metals such as beryllium, kirksite, and high chrome/nickel stainless steel

• Use: Wet or Dry

• Breakdown: 4

• Hardness: 2

Die Stone

Similar to the AM-2 but slightly harder with a slower breakdown. Engineered for use on both hard and soft tool steels. Provides consistent breakdown and fast cutting action.

• Available Grits: 150-600

• Methods: Hand Polishing or Air Profiler

• Materials: All types of tool steel and stainless steel

• Use: Wet or Dry

• Breakdown: 3

• Hardness: 3

AM-K Polishing Stone

White aluminum oxide stone with a medium-hard structure. Performs well on all types of mold steel. Primarily used dry for rough forming and removal of machining marks. Lubricant is typically used with the finer grits. Many polishers use the 400 and 600 grit AM-K for finishing plastic molds and blow molds.

• Available Grits: 100-600

• Methods: Hand Polishing or Air Profiler

• Materials: All types of mold steel including A2, A6, D2, DC53, O6, S7, and P20.

• Use: Wet or Dry

• Breakdown: 3

• Hardness: 3

AS-H Polishing Stone

Similar to AM-K but slightly softer and works well on tool steels as well as non-ferrous materials. It conforms quickly to varied pre-shaped surfaces. We suggest always using a lubricant with AS-H. More suitable for hand stoning but can also be used in reciprocating profilers.