Boride Mixed Series 4-Stone Boxed Set 6" x 1" PPA

Boride Mixed Series 4-Stone Set for WorkSharp PPA combines four aluminum oxide sharpening stones with an emphasis on tool steels: AM-8 F220, Orange EDM F400, T2 F800, and AS-9 F1200. The progression covers initial sharpening through fine edge refinement with the Work Sharp Professional Precision Adjust knife sharpener.

The set alternates harder and softer bonds through the progression: harder AM-8, softer Orange EDM, harder T2, and softer AS-9. This selection combines the shape retention of the harder stones with the more readily renewing abrasive surfaces of the softer stones.

AM-8 F220 starts the progression with a hard structure, slow breakdown, and good shape retention. Orange EDM F400 follows with extra-sharp aluminum oxide grain for fast, consistent cutting and further bevel refinement.

T2 F800 continues edge refinement with a hard bond and slow breakdown. AS-9 F1200 completes the progression with a softer structure and smooth cutting action for the final fine-abrasive stage.

The stones are mounted on ferromagnetic steel blanks in the PPA form factor, attaching directly to the magnets in the original PPA stone holder. Alignment holes engage the holder's locating tabs to position each stone and keep it stable during use, allowing quick changes through the progression.

Use the stones with a suitable sharpening lubricant.

When changing between stones or switching to the original PPA abrasives, check the sharpening angle and adjust it as needed to account for any difference in thickness.

How to Choose Boride PPA Sets

Boride PPA sets offer two four-stone progressions for the Work Sharp Professional Precision Adjust knife sharpener. Choose T2 for an all-around set with an emphasis on stainless steels, or Mixed Series for a selection focused on tool steels.

Oil Behavior

Oil Behavior describes how a sharpening stone interacts with oil during use. The property is especially important for vitrified and resin-bonded stones because oil can either remain on the working surface or be absorbed into the stone body. Oil behavior affects sharpening feel, swarf evacuation, loading tendency, maintenance, and long-term stone cleanliness.

Oil-retentive stones keep a stable lubricating film on the surface during sharpening. This improves swarf mobility, reduces surface drying, and creates a smoother, more consistent sharpening feel. Oil-retentive stones are suitable for long-term use with honing oil.

Oil-wicking stones rapidly absorb oil into the internal structure through capillary action. The working surface dries quickly, swarf removal becomes less efficient, and oil contamination may become difficult or impossible to remove completely. Oil-wicking stones are generally better suited for water-based sharpening.