Stone Grinding vs. Belt Grinding Skis and Snowboards
Belt grinding takes place during the tuning process in which getting an acceptable gliding surface using grinding belts only involves many more steps, moving through many grits of belt. Ski repair shops equipped with a stone grinder should definitely run the skis and snowboards through a stone grinder for best results and maximum ease of glide on snow.
Advantages of stone grinding skis and snowboards
• Improved maneuverability
• Instant response to direction changes
• Better direction control
• Faster, smoother, gliding
• Optimum edge grip for all slopes and snow conditions
When performing a ski or snowboard tune up, Stick Doc’s ski repair technicians thoroughly check the edges and the base for thickness to make sure there is enough material left to tune. New edge material is generally between 2-3 mm; if there is less than 1.5 mm, we will tune the skis or snowboard with extreme caution.
Stone Grinding Skis and Snowboards
The machines we use at Stick Docs to tune up your skis and snowboards have two sides to them. The belt grinder which is used primarily in to tune the base edges is on one side. The stone grinder which is used to remove polyethylene from the base to make it flat and to structure the base for the appropriate snow conditions is on the other side of the tuning machine.
By using the stone instead of the belt to get the base flat, we can do several things. The stone cuts the material from the base so there are no trailing fibers as one might find using a belt grinder, and the base is left flat instead of concave as with a belt grind.
The stone grind is much more efficient at removing the polyethylene so fewer passes through the machine can be made. This prolongs the livelihood of the ski and snowboard base for many winter seasons.
Ski and snowboard base construction
Ski Base Types
Ski and snowboard bases are made from UHMW (Ultra-high molecular weight polyethylene) which is a dense, abrasion-resistant thermoplastic with low friction properties. Ski and snowboard base material can be categorized into two general types, Extruded and Sintered. It is important to understand the differences in base material when tuning because of how easily the material is removed by the stone and how readily is absorbs wax.
Extruded bases are made from polyethylene pallets that are heated until molten and then forced under pressure through a die into the dimensions of the finished material. Extruded polyethylene is less abrasion-resistant than sintered polyethylene so it wears quicker and is removed at a much higher rate during the tuning process. It can be easy to repair but has little ability to absorb wax.
Sintering involves slowly heating a polyethylene powder under high pressure until the particles are melted and fused together. The particles are formed into a round disk similar to a large cheese wheel and the material is then skived off into a continuous sheet. The results are a much improved abrasion resistance which also makes the material harder to remove during the tuning process.
Sintered UHMW will absorb wax better than extruded base material, but can be more difficult to repair. Some ski and snowboard manufacturers use graphite during the manufacturing process which will harden the plastic, decrease the friction coefficient, and conduct electricity which helps to keep the base clean and fast.
Different patterns for a variety of snow conditions.