Stone grinding: Refresh your memory, and maybe your P-Tex as well
By: Karl Saidla (2009/02/04)
As most readers probably recognize already, most regular ski racers frequently get their skis stone ground. Some of you probably wonder what stone grinding is, and some of you probably wonder if it is worth the investment. In this short article I will try to summarize what stone grinding is all about in such a way that you can be better equipped to make those decisions.
Briefly, stone grinding is a process by which ski bases can be refreshed, flattened and structured (changing the fine pattern in the base material) using a special stone grinding machine specifically made for cross-country skis. An elite skier would normally have all his/her skis stone ground immediately after receiving the skis, and at least once per season after that. This doesn't mean that everyone else should do exactly the same, but it does demonstrate that the people who care most about having skis which perform optimally do most definitely make use of stone grinding.
Craig wrote a very good article about stone grinding last spring, and it is available here: http://www.xcottawa.ca/articles.php?id=1038 It appeared on our website in March, however, when many of us were probably already contemplating things like gear ratios for our new titanium road bikes or something like that.
As Craig mentioned in his article, in terms of ski bases, there are these factors which ultimately affect the ability of a ski to glide on snow: flatness (how flat the base is), smoothness (is the base free of “hairs” scratches etc), structure (the fine “pattern” of the base material) and wax absorption (how well does the ski base absorb wax). There is also of course, the psychological influence of having a ski base that looks more slippery than a snake in a grease pit. All of these factors can be modified in good ways by stone grinding, hopefully resulting in a “blow your hair back” experience for you.
Typically, skis are available in stores having been stone ground at the factory where the ski was made. While the structure might be appropriate for some types of snow conditions, and the ski might also be reasonably flat, odds are (for various reasons) that the pattern in the ski will be too coarse for the normal winter conditions we encounter in eastern Canada. Lately, these conditions have all been varieties of mind-numbing cold. Another potential problem is that the skis have been left around for a long time without being protected, in which case the base material can become “hard” and not very accepting of new wax applications.
Other situations where one might consider stone grinding include:
Skis which are were stone ground some time ago but have been used regularly for a significant period of time ( say, one complete season of skiing, for example). Repeated waxing, including heating of the ski bases, tends to result in the base “moving” around a bit and becoming something less than flat, and also becoming less adept at accepting new wax applications because of heat related changes to the material itself.
Skis which for one reason or another, have a structure in them which does not match the snow conditions in which you are typically using the skis.
An added benefit of stone grinding is that it makes waxing easier (the bases are flat, meaning that wax goes on and comes off more easily) and might actually prolong the life of a ski ( a flat base allows heat from the iron to be distributed more evenly, for example, making “burning” of the base less likely).
Some people will of course, be very interested in the actual structures that stone grinding makes available, and perhaps the merits of adding structure by hand (for example, with a rilling tool) vs. doing it by stone grinding. A complete discussion of these topics is, as they say “beyond the scope” of this article. Any reputable stone grinder will be more than willing to discuss this with you in depth in order to make sure that you wind up with a structre that is most appropriate for your intended use. I will, however, point out that stone grinding does not rule out using hand structure. A very common and sensible approach for people who do not have many pairs of skis to is have skis stone ground with a very fine pattern suitable to cold and dry snow conditions. Hand structure may be added as appropriate when the skis are going to be used for warmer conditions. Normally, structure added by hand is not permanent, and comes out with normal waxing.
If you've been reading carefully and you have never had your skis stone ground, at this point you are probably wondering how much it costs and where you can get it done. Normally, good quality stone grinding costs between $60 and $100 per pair of of skis depending on the complexity of creating whatever specific structure you wind up choosing.
XC Ottawa has been very pleased to work with three excellent stone grinding businesses who will all be very happy to perform proven, race quality work:
Gatineau Nordique Sport: http://www.gatineaunordiquesport.com/
Racing Grind Service (RGS): www.racinggrindservice.com/ or 418-832-7971
Caldwell Sport Specialties: http://www.caldwellsport.com/