The term "stone grinding" evolved, as a rotating stone in the Tazzari machine puts a pattern or grind into the base of the ski. To initiate the process, the specific pattern is entered into the computer screen. The machine has an extremely small sintered diamond that comes down onto the surface of the stone and puts a pattern into the face of the stone. The lines in the stone that remain in the surface of the stone press the lines into the base of the ski. The stone and the diamond used are for cross country skis specifically.
To start the process, the ski is pre-work with a medium-coarse pattern, or even by hand sometimes, and then polished to create an even flat-fine linear pattern. The ski is polished so that it is better able to accept the finishing structures. Most of the grinds consist of a compound structure with one pattern layered over another. A few structures for classic skiing consist of a single structure. All the skating ski structures that I use are compound structures.
The entire process of flattening, polishing and structuring the ski can take up to 1 hour for one pair of skis with the Tazzari RP-23 machine. The stone grinding process with the Tazzari machine of flattening, polishing and then structuring the ski is lengthy, but it has been determined by world class skiers that it creates a more effective grind and a lot faster ski.
Benefits of Stone Grinding
There are numerous benefits of stone grinding cross country skis, which is why it has become standard practice for the majority of skiers in the Scandinavian and European countries to have their skis ground at least once a year. Listed below, are the main advantages of stone grinding cross country skis.
- After skis are stone ground the bases are flat, most likely about 99% flat. A flat ski is faster, more stable, easier to wax when using an iron and easier to scrape. The majority of people find that it is more enjoyable and satisfying to work on flat, freshly ground skis.
- Stone grinding, in particular on skis that have been used a lot, removes the outer layer of the base which over time has hardened (not oxidized). It is generally accepted that the substance polyethylene does not oxidize. Most scratches are removed by grinding and the freshly exposed, softer layer of the ski base is better able to absorb wax.
- After proper stone grinding, not only is the base of the ski smooth, but equally important, the stone has made clean, sharp cuts into the base of the ski. Skis are fastest when the texture of the base is fresh and clean and the base structure matches the snow conditions. This explains why skis were stone ground on a daily basis by a lot of the countries at the Whistler Olympic venue.
- Commonly, particularly with skis with worn out bases, the skis are noticeably faster after they have been stone ground. Fast skis are more enjoyable to ski on and for a lot of young athletes they gain confidence when their skis are fast and stable.
- If skis are well maintained and kept flat, conservatively stated, they can be ground 5 to 10 times and in some cases 10 to 20 times. By having skis ground on a regular, possibly yearly basis, a skier can get 5 to 10 good years out of a pair of skis. Stone grinding in conjunction with good ski maintenance increases the longevity of skis.
- The bases of new skis are increasing flatter and smoother than they were in the past. But even then , these skis will be faster if you have them ground with an appropriate grind to your local snow conditions. In the Coast Mountain area, commonly, skiers want their skis to be fast in warmer, wet snow. In this situation, a skier may well benefit from having the skis ground with an appropriate -4C ° to +5C ° grind.