Swapping bindings without inserts in skis with metal?

[LC]

I took some FKS heelpieces on and off a pair of jib skis 4 times one winter for repairs (old Dynastars, no metal but a tough binding mat and 4.1mm drill bit recommendation). I put them through a lot of abuse that year and had no issues. Do it carefully, feel it out and you should be fine.

Or just buy a spare pair of bindings for $50.

[GeezerSteve]

Sounds like the conclusion is that, yeah, it works (regardless of metal or not), but you run the risk of a spinner if you crossthread or overtorque.

The better conclusion: Unless you form the epoxy plug via the upside-down method (see my prior post), it's merely a sheet metal screw connection in a quite thin Al alloy top sheet. (See vinman's post). Sheet metal screw connections are seldom designed to withstand on/off cycles. So, the answer is that you might get away with it for a few on/off cycles. Also, the possibility of cross-threading a screw in a tapped top sheet is zero unless you are a spastic knucklehead.

[bodywhomper]

A friend did this all the time. Used epoxy and i believe he coated screws with wd40. Pre insert days.

[altis]

What you need is Avdel Nutserts:

[1000-oaks]

^ Doesn't look like they're stainless steel, don't have threads on the OD, don't have full length threads in the ID, and are open bottom. Binding Freedom or Quiver Killer inserts would be preferable in every way IMHO.

[splat]

I've skied with guys who swapped bindings on metal skis, using the threads only and skied the shit out of those skis on very high dins. Without even a dab of glue. Taking three pair of skis and one set of bindings becomes feasible for trips. I create threads by drilling a smaller hole, coating the hole in epoxy and hand cranking in the screws. Makes a tough thread. If you're clumsy, I guess your could fuck up the threads taking the bindings off and putting the screws back in those threads. But if you're mindful of wtf you're doing, shouldn't be an issue on any ski, wood or metal. It's hard to bank on the epoxy totally sealing the hole if swapping out different bindings to other hole patterns in the ski. That's got to be a concern.

[1000-oaks]

The better conclusion: Unless you form the epoxy plug via the upside-down method (see my prior post), it's merely a sheet metal screw connection in a quite thin Al alloy top sheet. (See vinman's post). Sheet metal screw connections are seldom designed to withstand on/off cycles. So, the answer is that you might get away with it for a few on/off cycles. Also, the possibility of cross-threading a screw in a tapped top sheet is zero unless you are a spastic knucklehead.

I'm a fan of letting the epoxy cure with the ski base-up to theoretically keep the pool of epoxy in the thread area, but realistically an epoxy plug at the bottom of the screw is going to have a 4.1mm OD (assuming the ski was drilled 4.1mm) while the screw threads are 5.5mm OD. So the plug helps some (by making the screw "longer"), but doesn't really transfer much load to an alloy topsheet. Maybe you're calling the epoxy-soaked wood around the screw the "plug"? If enough soaks into the wood core, that could definitely enhance strength around the screw beneath the topsheet.

Splat would know better, but sure seems like epoxy soaks into wood. When installing inserts, I swab epoxy around the hole and let it sit for a few minutes, and much of it seems to disappear. I give each hole another dripping swab before threading in the insert, and thread them in a bit at a time in a round-robin pattern to prevent hydraulic injection of air or epoxy into the core. If you thread them in all the way in one shot, you definitely feel hydrolocking under the insert. It takes a little time for the pressure to be relieved by the slow flow of epoxy (or air) up through the threads.

[GeezerSteve]

right side up = epoxy might percolate into core away from screw

upside down = epoxy forms resin-soaked core plug around screw on backside of topsheet, like a nut on the backside of a plate

allowing epoxy to set upside-down was standard procedure in the shops where I mounted skis in the 1970s and 1980s, recommended by ski manufacturer reps

We confirmed the theory by sawing and looking at cross sections of several skis

Propensity of core to percolate varies, thus results may vary

Do whatever the hell you want to do, but IMV no thanks merely relying on a sheet metal screw connection, i.e., less than one full thread engagement in a material prone to become brittle via work hardening, when repeatedly cycling bindings off and on

[tuco]

I don't know about the 70's, but when I worked in the shop(late80's-late 90's) only 1 manufacturer called for epoxy for mounts--Hexcell. We used to mount a shitload of skis a day and constantly mixing epoxy for mounts wasn't happening, unless otherwise specified
Most regular screw holes are only going to accept about a drip or 2 of epoxy, certainly not enough to form a 'plug' under the top sheet, unless your mounting Hexcel, which required an epoxy kit and quite a bit more epoxy than a couple drips per hole. FWIW I think curing upside down is a good idea too, but it's effects are being overstated a little

[GeezerSteve]

Maybe I should have said "epoxy or glue." Some XC ski manufacturers were also recommending epoxy back then.

When I use syringes to apply epoxy the holes are accepting way more than a drip or 2 of epoxy.

[tuco]

Even with absorbtion I can't see getting anymore than a couple to a few drips in a 4.1X9.5 hole. If you're able to get that much in there, your screw is going to displace most of your epoxy/glue. I suspect you've got a shit load of epoxy stuck on your topsheet/ bottom of binding interface.You're using a syringe on a regular type mount?

[XXX-er]

30 yrs ago maybe a squirt of wood glue was good enough for mounting alpine bindings but now days there are more than a few super light skis some with carbon and we are now talking about mounting an AT or Tech bindings where slow set epoxy might be a better idea ?

[GeezerSteve]

I suspect you've got a shit load of epoxy stuck on your topsheet/ bottom of binding interface.

Well, I don't consider 4 or 6 drops (more for a helicoil, of course) of epoxy a "shitload." And if you're talking about epoxy between the top sheet and the binding, no, I avoid that.

You're using a syringe on a regular type mount?

I started using a syringe for HHs years ago -- Rainey supplied a syringe and epoxy with each HH binding -- and recently started again using syringes. Use of a syringe has been quite instructional. If I try to drip in epoxy with a toothpick, etc., I can only get in a couple drops because a bubble often forms under the dripped-in epoxy. With a syringe I can apply the epoxy down into the bottom of the hole, thus avoiding the formation of a bubble. I've never measured, but it seems that the hole will typically accept roughly 2X-3X more epoxy with a syringe, i.e., the air bubble is 1X-2X the volume of the epoxy that the hole will accept via dripping. It makes sense to me to avoid the bubble. Indeed, I'm pretty certain that the bubble results in epoxy getting between the top sheet and the binding.

I'm not telling anyone how do to their mounts. Nor am I overstating anything. I'm just offering how I do my mounts and offering my view that a sheet metal/top plate connection is not designed to be frequently cycled. I really don't give a shit what other people do, unless then are touring with me cuz I'm the guy who always ends up doing the field repair (of other people's mounts).

[tuco]

Ain't tryin' to challenge your mounting prowess, bro. At some point there is too much epoxy in the hole and your driving a screw in isn't gonna pressure inject all that epoxy into the wood and it's gotta go somewhere. Not that difficult to wet out the hole without a syringe. I was just asking a question out of curiosity.
Only time I ever had a problem was 1st year Terminators w/ 3 hole Riva cable mounted on TNC's(titanal layer). The Rivas didn't stand a chance.

XXXr- I use epoxy on all my mounts- pretty sure DPS and PMGear specify epoxy for mounts.

Lindahl- go with inserts as your going to have a hard time keeping moisture out of unoccupied holes

[GeezerSteve]

I'm a belt-and-suspenders binding mount guy cuz most of the hundreds of mounts I've done have been tele, 3-pin or tech, where pullout forces are greater than non-tech alpine bindings. We'll agree to disagree about the efficacy of syringe use. Russ Rainey had a reason for supplying them with all HH bindings.

[tuco]

Same.
Agree to disagree is fine with me.
He supplied it cause he realized that a certain percentage of the population was too retarded to be able to get glue into a hole.

[Lindahl]

Lindahl- go with inserts as your going to have a hard time keeping moisture out of unoccupied holes

Tape won't do it? (... in the garage. There won't be unoccupied holes while skiing, just one mount in them).

[daviski]

I've wondered about a good solution for the unused holes too -- Is there anything that could be melted in and then melted out that would not screw up a subsequent mount , wax for example would compromise future hold I'm sure. If the holes are clear of the other binding you could but screws in -or if there was a screw with no head and an allen wrench interface, like a trim screw (sorry all my comparisons are to carpentry) but finding one with the same thread- difficult

BTW I tried p-tex to permanently fill old screw holes and had surprisingly poor results


Lindahl, putting screws in the unused holes would certainly work for skis being stored w/out the bindings

[tuco]

Guess I failed at reading.
5200 as glue.
unused holes in garage should be fine the way they are. I recently fixed and remounted my iM103's and they were stored 7 or 8 years with open holes, but it's dry as fuck here

[AlpiNord]

It doesn't take that long to install ss inserts. The process provides the seal, easy to swap and you don't have to worry about the problems stated.

If that's not appealing, I'd think filling holes with machinable epoxy while installing screws would provide a reusable, sealed and threaded hole. Drilling deeper than the screw length provides room for epoxy in the bottom to protect the core. I haven't tried this, but maybe adding Vibratite during future mounts may work with alpine screws like machine screws in ss inserts.

[bodywhomper]

If i remember right, when rod johnson worked at marmot in the late 90's and early 00's, he had a few pairs of personal skis where he had multiple mount locations, using epoxy (i can't remember what kind of epoxy and i can't remember if he did the upside down thing) as threaded inserts, basically, he was another one doing what we're talking about now. this was in the days before inserts and for a reason that i can't remember, he didn't want to use helicoils - possibly because of the closeness between some mount holes. if i remember right, he never had issues with stripping the epoxy threads (though he was always careful), water logging a ski, etc. this was a technique that he used at rotte for testing and possibly at BD and chouinard. i know at rotte, his design team and testers used to play around a lot with mount location and moving around mount locations while in the field.

i always liked the syringe idea and rainey's use of it was an affirmation of a technique already in use.