Swapping bindings without inserts in skis with metal?

[Lindahl]

For metal skis, it's the metal that holds the binding screws, and not the wood core, right? Seems to me, you don't need inserts for those particular types of skis? I remember reading a while ago about how it doesn't matter for Volant Spatulas, due to the thick metal topsheet. Thinking the same holds true for metal skis like some Volkls and Heads, as well as others that tend to use a significant amount of metal?

Of course use waterproof wood glue to keep the moisture out.

[1000-oaks]

I only install inserts in skis I'm using with more than one binding, to keep out water. As long as you don't use epoxy (can stick to screw and tear out formed threads in ski when removed), don't cross-thread the screws and don't over-torque, I see no mechanical reason why mount #25 wouldn't be as strong as mount #1. Particularly in skis containing metal. On skis that will see annual swaps (spring or rock skis), I've been using silicone RTV instead of wood glue because it breaks loose easily but still keeps the water out. Also put a strip of packing tape over empty holes to keep out moisture when unmounted.

[XXX-er]

Are you saying that you think the metal in a ski will take the place of an insert for repeated swaps, sounds like a bad idea to me

[Lindahl]

I only install inserts in skis I'm using with more than one binding, to keep out water. As long as you don't use epoxy (can stick to screw and tear out formed threads in ski when removed), don't cross-thread the screws and don't over-torque, I see no mechanical reason why mount #25 wouldn't be as strong as mount #1. Particularly in skis containing metal. On skis that will see annual swaps (spring or rock skis), I've been using silicone RTV instead of wood glue because it breaks loose easily but still keeps the water out. Also put a strip of packing tape over empty holes to keep out moisture when unmounted.

Yeah, this would be for skis that get swapped annually. Moving bindings from rock skis to better condition skis. Good idea on the silicone RTV. I've been using wood glue. Are you saying that you're doing this for skis without metal, too?

Are you saying that you think the metal in a ski will take the place of an insert for repeated swaps, sounds like a bad idea to me

Yeah, that's the idea.

[adrenalated]

It would be fine for that purpose. It would be fine in a non-metal ski as well.

[Timberridge]

Are you saying that you think the metal in a ski will take the place of an insert for repeated swaps, sounds like a bad idea to me

^^^me too.

Most wood cores are made out of softwoods and the metal is Al based. Neither materials are known for their thread durability.

[XXX-er]

Metal in a ski is not the same as a steel insert using machine screws, so not a great idea for swapping every other week but for annual swaps you might be OK, I would use slowset epoxy for strength

hitting the screw heads with a soldering iron for 30sec will break epoxy loose, in fact anytime a screw won't budge I use heat before the screw gets fluffed cuz you don't always know how they were mounted

[shafty85]

For metal skis, it's the metal that holds the binding screws, and not the wood core, right? Seems to me, you don't need inserts for those particular types of skis?

I'm not sure that this is correct... It would mean you are relying on only a portion of 1 thread to hold the screw in...

sounds like a bad idea to me

+1.

[PNWbrit]

Seems a really dumb idea.

[1000-oaks]

If any mechanical engineers want to explain how this is a bad idea when done correctly (vs an old wives tale from folks who screwed it up), I'd like to hear it.

Don't think wear is an issue in real life, even if you erode 0.001" of load-bearing thread area with each swap (which isn't going to happen when the surfaces are coated with high viscosity glue), so what if you had to tighten the screw 1/100 of a degree more each swap? After 100 swaps you have to tighten the screw an extra degree? I can live with it.

[adrenalated]

If any mechanical engineers want to explain how this is a bad idea when done correctly (vs an old wives tale from folks who screwed it up), I'd like to hear it.

Don't think wear is an issue in real life, even if you erode 0.001" of load-bearing thread area with each swap (which isn't going to happen when the surfaces are coated with high viscosity glue), so what if you had to tighten the screw 1/100 of a degree more each swap? After 100 swaps you have to tighten the screw an extra degree? I can live with it.

This. As long as the threads are structurally sound (ie, be careful not to overtorque, or crossthread the screws when installing) the mount will be sound. In a metal ski, in a wood ski, in any ski.

BTW, I am a ME.

The purpose of an insert is A) to make it harder to fuck up the threads, B) to allow multiple mounts on a single ski without the need to plug/seal the unused holes and C) to allow more frequent and on-the-fly binding swaps without the need for glue and waiting for the glue to dry. Mainly C.

[1000-oaks]

The real problem with this is probably the plastic tabs in binding baseplate holes, which binding manufacturers provide to hold screws in correct position during shipment and make mounts faster for shop techs. Unless a person files out or drills out the plastic tabs with a 5.5mm drill, the tabs won't allow you to feel the threads in the ski, making it easy to cross-thread during remounts. Pull-outs after cross-threading screws is likely the reason for this popular myth, IHMO.

Solution is to drill out the tabs every time you get a new pair of bindings, which also helps align the screw threads with the tapped ski threads during the initial mount.

[Soups]

FWIW I got a spinner on a Spatula after reusing the toe holes a third(?) time. Bad idea IMHO. Not that I'm saying it couldn't work if you are perfect everytime, but how would you ever know that until its too late.

[1000-oaks]

Could have been overtorqued during any of the three mounts and on the verge of being a spinner. Kind of like rolling the dice playing craps; your chances of overtorquing & having a spinner are the same on every roll.

Not playing does prevent losing though, can't argure that. But also prevents winning (more skis, less investment in bindings).

[DropCliffsNotBombs]

If you plan on taking bindings off and on more than a few times, you really should go with inserts.
Metal laminates are no more reliable at retaining binding screws than other materials once you start reusing the holes. They'll give you spinners just as easily.

P.S.- Inserts have super strong pull out resistance (compared to standard binding screws) and are a viable option even if you never plan on swapping bindings.

[saxon]

You could probably summarize most of our opposition with, "why would you not want to use inserts?" To me, putting inserts in a ski is so trivial (in effort and cost) it's worth it to do with every mount. But I think it was Lindahl (the OP) who ranted last year about why so many skis were on gear swap with inserts and he felt like the inserts made the skis less valuable to him. Even if it wasn't him, there's obviously a group of people who actively don't want inserts in their skis, so the basis of my opposition is certainly irrelevant to them.

[XXX-er]

If you wana reuse binding holes in a ski carefuly rotate the screw backwards by hand with a PZ3 bit so you can feel the screw dropping into the original thread then go forward ... prevents crossthreading

IME it was often the engineer who fucked everything up

The fixit guy made it run

[GeezerSteve]

No thanks. Screw/Al alloy top sheet connection = sheet metal screw/sheet metal connection, i.e., <1 full thread of engagement, very small bearing surface. You really don't want to cycle that more than a few times, lest you risk a failure. The hole in the top sheet deforms a bit with each cycle, which can do two things: (a) work harden the edge of the hole, making it brittle and (b) pull the topsheet out a bit with each cycle slightly enlarging the hole.

A properly installed ski helicoil in a ski with a metal top sheet can withstand many on-off cycles. It exposes the core to weather when not in use, but that's not a problem if you are storing the skis in a dry place with duck tape over the holes when the bindings are off the ski.

BF/QK inserts if you are using >1 binding per ski (if that's your thing)

ETA: IME when mounting a metal top sheet ski it's a good idea to use plenty of epoxy and turn the ski upside down while the epoxy sets. This results in the screw being anchored in a resin/wood plug positioned up against the top plate. If done right, it's a bomber connection, but you need to redo it with each on/off cycle.

[Lindahl]

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. If that happens, I can always add inserts at that point.

I'm pretty smooth with binding installs, never had issues with spinners, ever. Sounds like a go-ahead.

[shafty85]

This. As long as the threads are structurally sound (ie, be careful not to overtorque, or crossthread the screws when installing) the mount will be sound. In a metal ski, in a wood ski, in any ski.

Theory and reality are very different things. You would have to have the threads in the exact same place every time with zero variance in thread location and torque. The odds of this being accomplished must be close to zero when doing something as inexact as installing ski bindings by hand. I would definitely feel comfortable taking bindings on and off a ski once or twice without inserts, but beyond that, sign me up for inserts or helicoils.

[Muggydude]

Personally I never understood why people disliked buying used skis with inserts. I'd rather have a set of inserts in my skis than plugged holes. Easier to reuse (never degrades the hole), seals better, and contribute to a stronger binding mount area than a plug. Only downside is you need a little extra space to drill new holes, but personally I think you can get as close as 11-12mm wothout issue.

[skimaxpower]

I've seen bindings pull out of metal skis plenty of times. Removing and re-using binding holes only adds to the risk of water rotting the wood and binding pull out.

If you want to swap bindings on a regular basis, install inserts. Remember, bindings are safety equipment. If you didn't care about safety, you'd just bolt your boot to the ski and save $200.

[Shorty_J]

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. If that happens, I can always add inserts at that point.

I'm pretty smooth with binding installs, never had issues with spinners, ever. Sounds like a go-ahead.

I agree with the "no" crowd but this is a reasonable compromise if you have the repair materials on hand and at the ready.

[1000-oaks]

The odds of this being accomplished must be close to zero when doing something as inexact as installing ski bindings by hand.

With the plastic tabs drilled out of the binding baseplates (so the screw can turn freely), and you turn the screw backwards by hand slowly until you feel the lead thread drop into the thread start in the ski, I'd put the odds of getting it right at about 98%. If you start turning clockwise and the screw doesn't turn into the existing threads easily, back up and try again. I've never cross-threaded a screw doing it this way. If the screw threads are following the threads already formed in the ski, it doesn't take much effort to spin the screw into place. If you crank the screw in hard, it's cross-threaded and time for an insert.

Someone uncomfortable with doing this should certainly install inserts and I'm all for whatever gives folks peace of mind. I use inserts regularly myself. But to say it "makes the mount weaker" even when done correctly is illogical and isn't based on material or mechanical properties, as confirmed by our in-house engineer.

[Vinman]

The metal layer in skis is maybe .4-.6mm thick of an aluminum alloy. It won't be a strong as a stainless steel insert. I think you could swap bindings a few times but it isn't something I'd do a whole lot of.

As for cores, they are supposed to be designed to hold a minimum of 5n-m of torque, and something like 300lbs of straight pullout force per screw. Most soft woods are not suitable for this. Binding screws should be torqued to
4n-m, which isn't really much if you've ever used a torqe limiting screw driver.