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Polishing Stones By Application

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.

  • Available Grits: 100-1200
  • Methods: Hand Polishing or Air Profiler
  • Materials: All types of tool steel as well as stainless steel and non-ferrous materials
  • Use: Wet only
  • Breakdown: 4
  • Hardness: 2

General Purpose Polishing Stones – Silicon Carbide

CS Polishing Stone

Black silicon carbide stone designed to breakdown rapidly and conform to details. Mostly used for hand polishing, we do not recommend using CS is reciprocating profilers. Used on all tool steels as well as for roughing out some non-ferrous materials such as kirksite, copper and beryllium.

  • Available Grits: 150-1200
  • Method: Hand Polishing only
  • Materials: All types of tool steel as well as non-ferrous materials such as kirksite, copper and beryllium
  • Use: Wet or Dry
  • Breakdown: 5
  • Hardness: 2

CS-M Polishing Stone

Green silicon carbide stone with superb cutting capabilities. Non-loading with a medium-soft hardness for excellent polishing. Produces a silky matte finish on all pre-hardened tool steels from 28Rc SAE 4130 through 60Rc A2 and M2. The most popular stone used on H-13 and can be used to roughout beryllium, copper and kirksite. A good choice for stoning contours and radii as it contours nicely to the tool. 

  • Available Grits: 120-1200
  • Methods: Hand Polishing or Air Profilers
  • Materials: All pre-hardened tool steels and non-ferrous materials, works particularly well on H-13
  • Use: Wet or Dry
  • Breakdown: 4
  • Hardness: 2

CS-HD Polishing Stone

Harder structure and slower breakdown than CS or CS-M. Can be used to polish even the hardest die and mold steels. Particularly great for finishing dies ranging in hardness from 47Rc to 63Rc. Often used for the removal of EDM scale as well.

  • Available Grits: 120-1200
  • Methods: Hand Polishing or Air Profilers
  • Materials: All mold and die steels, as well as H-13, cast iron, heat treated nitrite P20, tungsten, chromium, and titanium
  • Use: Wet or Dry
  • Breakdown: 3
  • Hardness: 3

Specialty Polishing Stones

RASP Polishing Stone

Our most versatile all-around finishing stone. Offers outstanding cut and finish on all tool steels, aluminum and even EDM surfaces. Excellent for flat lapping and contours quickly with a moderate to fast breakdown.

  • Available Grits: 80-1200
  • Methods: Hand Polishing or Air Profiler
  • Materials: All mold and die steels, stainless steel, aluminum, non-ferrous materials and EDM scale
  • Use: Wet or Dry (use lubricated with softer metals)
  • Breakdown: 4
  • Hardness: 2

PC Polishing Stone

PC (polisher’s choice) is a quick contouring stone designed for rapid stock removal on tool steel, stainless steel and non-ferrous materials. Engineered to be used as a final finishing stone on molds requiring a near mirror finish. Must be used by hand with a lubricant to be effective.

  • Available Grits: 150-1200
  • Methods: Hand Polishing only
  • Materials: All mold and die steels, stainless steel, aluminum, and other non-ferrous materials
  • Use: Wet only
  • Breakdown: 4
  • Hardness: 2

T2 Polishing Stone

Fast cutting stone that provides a silky, smooth finish. Great for polishing high quality mold steel such as P20 (most popular), H-13 and 420 stainless. Use wet either by hand or reciprocating profilers.

  • Available Grits: 150-1200
  • Methods: Hand Polishing or Air Profiler
  • Materials: High quality mold steel including P20, H-13, 420 stainless
  • Use: Wet only
  • Breakdown: 2
  • Hardness: 4

T4 Polishing Stone

Specially treated soft aluminum oxide finishing stone engineered for finishing aluminum and soft metals. Cuts fast and breaks down quickly while leaving an excellent finish.

  • Available Grits: 150-1200
  • Methods: Hand Polishing or Air Profiler
  • Materials: Aluminum and soft metals, also works on stainless and other tool steels
  • Use: Wet only
  • Breakdown: 4
  • Hardness: 3

TH Polishing Stone

Hard structured aluminum oxide polishing stone for polishing slots, ribs, letters, and hard-to-reach spots. Holds its shape making it ideal for polishing sharp corners and details. Excellent for EDM surfaces and performs well on all types of tool steel. Provides a load resistant, smooth cutting action.

  • Available Grits: 150-1200
  • Methods: Hand Polishing or Air Profiler
  • Materials: EDM surfaces, all types of tool steel
  • Use: Wet only
  • Breakdown: 3
  • Hardness: 3

AO Polishing Stone

Medium-hard aluminum oxide finishing stones pre-filled with lubricant. Offers excellent breakdown characteristics and retains their shape, making them ideal for polishing mold cavity details.

  • Available Grits: 120-1200
  • Methods: Hand Polishing or Air Profiler
  • Materials: A2, A6, D2, DC53, O6, S7, and P20, as well as EDM surfaces (grits 220 and 320)
  • Use: Wet only
  • Breakdown: 3
  • Hardness: 3

900-F Polishing Stone

Super-fine stone with excellent breakdown properties for final finishing prior to mirror finishing. Works especially well on P20 mold steel with a hardness ranging from 29Rc to 32Rc as well as 420 stainless steel. Used for hand finishing operations only.

  • Available Grits: 900
  • Methods: Hand Polishing only
  • Materials: All types of mold steel, works particularly well on P20 and 420 stainless steel
  • Use: Wet only
  • Breakdown: 5
  • Hardness: 0