How Many Holes can you Drill in a Ski?

We got the following as an email, figure a response was in order. Steve, sure, we re-mount skis all the time. Our comments below yours…

Lou- Sure have enjoyed your blog for the past year or so, in fact, it’s the only blog I make a point of reading nearly every day. You motivated me to take up randonee skiing humping up & down A-basin every weekend while my wife was learning how to snowboard at an enthusiastic 54; get up to Jackson for closing week, (yes I was there in the award tent scamming free beer after the race thinking, “man with this kind of swag, I’m definitely entering next year”), and regret tossing that lime green pair of 175cm TUA skis with the old Ramer bindings I bought new back in ’85 or so. Which leads me to the point of this email. I picked up a pair of Havocs at the end of the season that were mounted with tele bindings. I love the ski but want to take off the tele bindings and put on a pair of Dynafits. Have you done this type of retrofit before? My guess is lots & lots. I have some basic questions like what should I fill the old holes with and what if the new layout partially overlaps the old holes? Fill then drill? I thought this might be a good subject for a blog, what with the current ski sales frenzy, other folks might be in the same situation. Any advice would be appreciated and thanks. Saw new snow high up in the Mosquito range this weekend. It won’t be long now! Still as crazy about skiing as 30 years ago– Steve

Steve, thanks for throwing away those lime green Tuas with Ramers — I found them in the dumpster and they’re now for sale on Ebay as valuable antiques.

As for re-drilling skis, there is a traditional view in ski culture that drilling extra binding holes devalues a ski and weakens it to the point where one should be cautious about using it hard. This might still be true for large aggressive skiers using non-release telemark bindings or DIN 16 touring binders set to max. Otherwise, read on — you can drill a bunch of holes in most skis (though some ski models are known to be weak and indeed should only have one set of holes).

Thanks to the needs of telemarkers, many if not most of today’s backcountry touring skis have an incredibly beefy reinforcement in the binding mount area. (Though a recent trend has been to back off from this to save weight, so be sure to research what you’ve got). More, nearly all modern skis are overall super strong. I’ve skied for years on planks Swiss-cheesed with up to four sets of binding holes and never broken a ski under the foot or had a binding rip out in normal use. (Bear in mind I’m not an aggressive skier, don’t fall that much, use release bindings set to release, and mount bindings using the methods detailed below.)

So, how to do the deed? Lay out your new binding holes on your backcountry skis. If using a mechanical jig you can look down through the drill bushings and check how close to the old holes you are. Once you decide on a position, drill at will if you’re far enough from existing holes. If you’ve got an overlap situation, read on. If using a paper template, punch out the screw locations with a paper punch so you can slide the paper around and see how your new holes relate to existing.

If the new bores don’t overlap the old holes, re-mark with your centerpunch and drill away. If you overlap by only a few millimeters, simply move your binding location accordingly, usually rearward for recreational and backcountry skiing. Most touring bindings have enough heel unit adjustment to tweak so they’ll always miss existing holes, it’s the binding toe you might have to move back a hair. A small change in boot fore/aft location is totally within spec for ski performance, and as long as the edges of your new holes are a few millimeters from the old, you’ll be fine drilling and using the new ones. (You’ll still want to fill the old holes, but a quick job with plastic plugs or 5-minute hardware store epoxy will suffice.)

If your new holes must overlap the old, then you need some careful fill work. I usually fill the old holes with something like JB Weld or epoxy steel, and poke steel wool in the hole as well. It’s important to fill the holes completely with some sort of hard filler, do so by poking the epoxy and wool in with a small probe such as a tiny drill bit. Use the slower curing epoxy as it’s stronger than the 5-minute versions and makes less heat. Wait 48 hours at room temperature for a full cure before the next step.

After the epoxy hardens in the holes (48 hours at room temperature), I smooth it off with a sanding disk in a grinder. Whatever works for smoothing is fine, just avoid anything but cosmetic damage. If the holes don’t overlap but are super close to your new ones, still fill the old holes with epoxy steel and steel wool, otherwise fill the holes with regular 5-minute epoxy, or even use the plastic plugs available from ski shops.

Drilling overlapping holes is the tricky part. If the ski doesn’t have a metal layer, start the drilling with a small bit, then step up through successively larger bits to your final size. The idea is to prevent the edge of the existing hole from forcing the bit to the side and only drilling the epoxy out of the old hole.

Dealing with a metal layer is tougher. If your drilling begins in the metal, stepping the bit sizes will usually work. If you start in the epoxy fill, do the step-up routine till your bit encounters the metal edge. Then, instead of going to the next size bit, pull the drill most of the way out then hold the spinning bit against the metal edge so it eats sideways a small amount in the direction the hole needs to grow, thus “egging out” the hole. We’re talking a millimeter or less of this, so no big deal. If you’re a craftsman and have a rotary grinder (e.g., Dremel), you can “egg” out the holes using a small rotary cutting bit, which works much better. Take care not to “egg” too far. Keep it tight.

Finish the hole with the correct size bit. Don’t fret if one or two of your holes end up slightly off layout, as rando bindings have a small amount of tolerance for this (place screws in on-layout holes first, then place others.)

If you mess up and end up drilling the epoxy out of an old hole, just re-fill and try again with a little side pressure while drilling. Tap the holes if you’ve got a ski mounting tap, place all binding screws with the same long-cure epoxy you used to fill the existing holes, don’t over torque, let cure for 48 hours, and you’re good to go backcountry skiing!

(Note, it’s possible that the epoxy you use for your final screw placement can soften the epoxy fill in the original holes. I recommend saving a blotter with the cured fill epoxy on it, and smearing some of the screw placement epoxy on the original. You can thus observe any problems. One reason for using slow cure epoxy is the lack of heat which can soften existing epoxy or ski resin layers.)

Another method of filling old holes for re-drilling is to epoxy hardwood plugs. This method has its advantages as the plugs can be more structural than the epoxy and steel wool method. Problem is the wood is super sensitive to moisture, so personally I always use the all-epoxy method. If you use hardwood plugs, cover them with epoxy when you do the final binding mount, for 100% defense against water. Yet another technique is to carefully bore holes for inserts such as Quiver Killer. Whatever the case, if you have access to a milling machine or high quality drill press, drilling overlapping holes can be done much more easily by clamping the ski to the machine and boring holes that are forced into perfect position by the rigidity of the machinery.

(Note about taping holes and bit sizes: Ski shops use special drill bits for drilling skis, usually 4.1 mm for skis with metal layers, and 3.9 mm for skis without metal. If you mount a lot of backcountry skis, it’s a good idea to buy some special drill bits from an outfit such as Slidewright, along with such bits, buy a threading tool (tap) to thread the holes. In my experience, it can be okay to use a slightly larger 5/32 inch drill bit for the final size hole, without a tap. But when you don’t use a tap you run the risk of the binding screw augering the JBWeld out of the hole and reversing all your hard work. If you do choose to not use a tap, especially with non-metal skis, use plenty of pressure as twist the screws in so they start to thread right away, don’t over-tighten and strip the holes, and indeed use epoxy in the holes when you place the screws (to remove epoxied screws, lightly heat with soldering iron before twisting out.)