Your skis undergo a thorough grinding process.
The grinding process is complex, demanding a lot from both the person grinding and the grinding technology. The grinding is done by moving the skis over a grinding stone which sets the structure in the base. The pattern in the structure is set by the pattern on the stone, and it’s crucial to set the correct structure on the stone. In turn, the pattern on the stone is set by a diamond which cut the lines on the stone.
The grinder needs to know several parameters that can influence the grinding process. Every time we are changing the structure, the diamond gets more wear, and its properties slightly change. There are several different diamonds; some with different needles and are different sizes. Another variable to consider is that there are no grinding stones that are equal at the start. They are made from burnt sand and glass and will always vary a little in hardness, composition and density. We carefully choose specific stones for certain structures.
Put differently; we have to adapt our process to each batch of grinding to compat the differences in the stone and diamond. But there are some common steps in the process. Below is a description of these steps, including images and elevation profiles from the base structure as it changes from step to step. This is an example from a warm ski.
Step 0: Cleaning
Remove any glider from the ski by scraping and brushing so that the ski is very clean. It is important to prevent the grind machine from being contaminated since it can pick up dirt and wax from the ski.
We felt the ski below had a bit too course structure based on the ski’s properties. As you can see in the picture, the structure is both sharp and course. Therefore, we decided to go for a less warm grind, although still on the warm side.
Step 1: Planing
The first part of the grinding is called planing. This step makes the skis completely flat. This part of the process varies and a new pair may take 2-3 passes while an old pair might need up to 10-15 passes through the machine. Used skis often have some blemishes and can be uneven over time. This requires that we remove a larger part of the base.
It’s clear how much more even and cleaner the structure is after the planing.
Step 2: Polishing
Skis have a linear structure in the base after we are finished with the planing. The harshness of the structure is tempered by a polish grind. The polishing process requires the ski to be passed through the machine 2-3 times. After the polishing, the base will have a smooth and even surface with very little structure. The RA is usually around 1.4 - 1.9 after this step.
For cold grinds with RA around 2.0 - 2.5, it’s crucial to get the RA-value as low as possible after polishing. For the warmer grinds it’s not so important that the RA value is as low after polishing, because we are setting structures that are significantly coarser after the polishing.
Step 3: Structure
Two runs through the machine remains, to set the final structure. All our grinds are 2 different grinds put together. First run we set a base structure, which is coarser than the final product. The second time we are setting a structure with a lower Ra. The second run also breakes the lines set by the first run.
Step 4: Measure, Wax and Deliver
We measure the RA value after the skis have gone through the machine the last time. The RA value and the grind are noted on the sticker that’s put on the skis. Then the skis are cleaned, wax for transport and is delivered to the customer.