Ski inserts, the same ones used by the snowboarding industry, are for attaching
a binding to a ski. Compared to the traditional method of mounting
bindings with wood screws, inserts have greater pull-out strength reducing the
likelihood of screws ripping out of a ski. Aside from making a ski safer,
inserts allow the swapping of bindings from ski to ski on the hill without the
need for extra drilling. By installing a "pack" of inserts, they also
allow the skier to change mounting locations on the same ski with ease.
Inserts are usually manufactured from stainless steel to resist corrosion.
To prevent epoxy during layup from ruining the threads, they also come with caps
(shown in black below) which are drilled out during the finishing process.
These caps often come magnetized to aid in drilling process. Keep in mind
that the inserts are covered up by the ski's topsheet during layup making the
inserts difficult to locate. By using iron fillings, the magnetized caps
are easily detected for a fool proof method of locating the inserts.
The dimensions of inserts can range anywhere in height with any type of threads.
The most common thread type is M6, the standard in the snowboard industry, with
a height range of 7mm-10mm.
Step 1: Mark Center Lines Begin by first marking the center
lines on the top-side of the wood core. The center lines should align the
desired mounting location (chord center, boot center, etc.) and along with the
vertical axis of the ski.
Step 2: Set Up Binding Template Still working
on the top-side of the core, align your binding template of choice carefully
with the center lines and secure with tape. Next, use a nail and hammer to
center punch all the screw locations. These center punches will help guide
the screw bits to allow for accurate drilling.
Step 3: Drill Pilot Holes Now drill small
pilot holes (about 3/32" diameter) into each of the screw locations marked in
the previous step. It's best to use a drill press if available, however, a
steady hand and a power drill should work fine. Just try to keep the holes
as perpendicular to the core's surface as possible. Remember that we are
still working on the top-side of the core.
Step 4: Counterbore After all the pilot holes
have been drilled, flip the core over so that the bottom-side (base-side) is
exposed. Use an appropriate sized forstner (shown in the middle
below) or a spade bit (shown on the right below) to counterbore the holes.
The size of the bits should just be large enough so that the flange of the
insert can sit inside the bore. In this example, we used 5/8" diameter
Slowly counterbore the holes until you have reached the desired
depth. This depth can be determined by first measuring the core's
thickness (y) and the insert's height not including
the flange (x).
The difference of the two measurements is the depth that you
will need to counterbore the holes.
Step 5: Drill Final Holes Complete the
drilling process by drilling out the pilot holes so that inserts can fit
through. The diameter of the holes should measure as close as to the
diameter of the insert shafts as possible. Push the inserts into the holes
and check the fit. The inserts should sit snugly into each hole while
being as flush as possible with the top of the wood core. It's not
extremely important to be flush but just make sure that the flanges do not
protrude beyond the base-side of the core. Otherwise, there will be
impressions of these protruding flanges in the ski's base during the pressing
which could make for an uneven base.
Step 6: Secure with Epoxy After all the
inserts have been tested for fit, secure the inserts with epoxy. Begin by
using some tape to cover the top-side of the insert holes. The tape helps
prevent epoxy from leaking out when the core is flipped over.
Flip the core over to expose the base-side and add just a small
amount of epoxy into each hole. Make sure that you have most of the hole
along with the counterbores wetted out with epoxy.
Finally, place the inserts into each hole using a hammer to set
them into place. Fill up any visible gaps with epoxy and make sure to wipe
up any excess adhesive.
After the epoxy cures proceed to the next step of cutting the