How to Base Grind Skis

I've covered ski tuning in the past, which is the process of sharpening edges, filling gouges and applying new wax to a pair of skis. But every once in a while you need to overhaul your skis, known as a base grind. There isn't much information online about DIY base grinding, but the principle is straightforward and with some basic woodworking tools, you may be able to do it yourself. This post is about how I did a base grind on my skis. Ski-techs may recoil at this, and use at your own risk (skis are expensive!), but this worked for me and saved a bunch of money at the ski shop.
First it is useful to understand how skis are constructed. Skis are built around a core, which is either made of foam or laminated strips of wood with specific flex properties. The core is sandwiched by two composite layers (fiberglass matting, kevlar) on the top and bottom and sidewalls on the sides. On top goes a top sheet (and graphics) and on the bottom goes a base with metal edges. Everything is held together with special fiberglass resin. Simple right? Over time the bases may get badly worn. They will have gouges, they may cup and the edges may be badly worn and beveled from tuning and hard skiing. Base grinding will remove these imperfections by grinding away at the base, just like sanding removed imperfections in wood. I started by adding ptex to fill in gouges that may be deeper than I want to grind. Ptex is a super hard composite material that you light on fire and drips into gouges. It bonds with the ski base and fills in the hole. Usually you scrape the ptex level with the ski and then wax the skis normally, but there's no need when doing a base grind. As I obviously don't own an expensive stone ski base grinding machine, I'm using a variable speed belt sander. Though that belt looks like a heavy grit belt, I actually used a fine 220 grit belt on the skis. I also ran the sander at the slowest speed I could, did light and fast passes and checked the ski frequently to ensure I wasn't removing too much material. If you sand off the base of the ski you've basically ruined the pair. My pock-ridden were quickly transformed into almost new looking skis. The gouges and scraps were gone. Scraps on the sidewalls disappeared. The bases looked clean and new. I went over the side of the edges again as well, as the sander only hit the bottom of the edges.

As I removed the wax on the skis along with the imperfections, I had to apply new wax. As I was not simply rewaxing previously waxed skis, I had to use a lot of wax to ensure good, even coverage. I believe ski shops may even wax, scrape and rewax skis to ensure a good base. Look at these pretty maids, all in a row.
I skied this pair following this project and wow. The base grind really gave them another lease on life. The skis hold an edge beautifully on hard pack and track through crud beautifully. I was used to getting bounced around and skidding through hard turns. I had forgotten what these skis were like when they were new. The turns were fast and precise. Did I mention fast? I was beginning to think that these skis would need to be replaced soon but now I'm thinking I'll at least get next year out of them. Taking a belt sander to your skis sounds intimidating (but so does taking a drill!) but if you are careful and take your time, you can breath new life into a tired old pair of skis, without shelling out a good portion of a new pair of skis to pay a shop to do a base grind.

PS- here's another great DIY ski tuning and repair website.