Despite their remarkable cutting speed, Sigma stones are little known outside of Japan. Significantly faster than any other stones we have tested; the 1000x stone cut O1, A2, and M2 steel 10-15% faster than 1000x Bester/Imanishi stones, and between two and five times faster than 1000x water stones with less durable abrasive or stronger bonds.
Sintered under heat and pressure, the resulting stone readily releases new, aggressive particles during use. While these stones wear at a more rapid rate than those with stronger bonds, this is offset by the extremely fast cutting action, resulting in reduced stone wear, since you can achieve comparable material removal in far fewer strokes.
The 240x is for rapid steel removal, the 1000x produces a primary bevel and the 3000x quickly establishes a micro-bevel. The 10000x and 13000x stones provide a fine finish. All require only a few minutes of soaking before use.
To read a comparison of our water stones, click the "Tech" link below.