Stuck binding screws? - Use a Hand Impact Driver

[Gunder]

Does your experience include controlled pullout tests?

Zeno's full test results were on the original TT. I believe he did a second batch of tests. He occasionally posts on TGR so maybe he'll see this and chime in. I can't find a link now that the original TT has been dead for awhile. Zeno had a pretty good sampling in this tests, numerous skis w/ different cores (including foam [Atomic], I recall), tapped vs. untapped, "waterproof" wood glue vs. epoxy. Of all the combos tested, tapped + epoxy required the highest pullout forces to achieve failure.

As I said above, my theory re tapping + epoxy = stronger is that cutting threads into the core with a tap enhances the opportunity for the epoxy to penetrate the core material, thus forming a female threaded core/resin plug. Tapping also allows the installer to use less torsional force to screw the binding down flat on the ski deck.

When I read Zeno's tests I was skeptical and performed my own, less formal, bench tests in a half dozen skis, some wood core, some foam core and even a hemlock 2x4. Although it my tests did not have the controls of Zeno's, my testing persuaded me that tapped holes resulted in a stronger connection in both wood and Atomic foam cores.

Re rust: I have seen a bit of rust on some epoxied screws, but nothing like the extent of rust I've seen on screws installed with alleged "waterproof" glue, e.g., Titebond II or III. Again, I'm talking about PNW touring skis, which are frequently exposed to moisture. Maybe this doesn't matter much for alpine mounts used only in cold weather when there's not much ambient moisture.

It did back in college when I was working on an all carbon ski, but that was over a decade ago, and I have no idea what I ever did with the data, since I havent done anything with it since.
I'd really like to know if his test also included different drill bit dia. As using the proper dia. bit has a pretty big effect. Also, binding screws (most wood screws for that matter) are self tapping for a reason...

[GeezerSteve]

I seem to recall that he used two different drill bit diameters.

Right, of course, wood screws and sheet metal screws (more similar to ABS) are designed to be self-tapping. That doesn't necessarily mean that tapping certain materials will not enhance purchase.

[XavierD]

I just mount skis using the correct drill bit, wood glue, and counter sinking. Never had a problem.

Over the last two years I started doing a partial tap on skis with metal and some higher strength top sheets to reduce creating volcanoes.

I think you all are making much adu about not much. I think not buying skis with shitty cores would be a better use of your energy.

[galibier_numero_un]

... I think you all are making much adu about not much. I think not buying skis with shitty cores would be a better use of your energy.

Of course, you're right, but without this obsession, we'd have to start thinking about climbing, mountain biking etc., this time of year

Cheers,
Thom

[GeezerSteve]

I think not buying skis with shitty cores would be a better use of your energy.

Evidence to support this sweeping accusation? If we accept your declaration that those tapping + epoxy buy skis with shitty cores, you prove my point. I've done hundreds of mounts, many of which are subject to high pullout forces (tech toes, tele) without any pullouts, so that's proof that my mounting methods are sound notwithstanding all of those shitty cores. Thanks for the unintended compliment.

[Rip'nStick]

Thanks Gunder. That kind of information is why I am still here. That and argueing with douchebags on the internets

[GeezerSteve]

Of course, you're right, but without this obsession, we'd have to start thinking about climbing, mountain biking etc., this time of year

Or skiing, which we plan to do this weekend and the next and the next. That, and I mounted two pairs of friends' touring skis yesterday, tapped + epoxy.

[gregL]

Way to get after it, Steve.

I'm not so sure about the fresh epoxy penetrating the core material - my theory is that tapping makes the female threaded surface fit the male surface more accurately, creating more surface contact. Plus it reduces outward stress on the hole. I also turn the ski upside down, having mounted a few Hexcels in my time.

[tuco]

I'm not so sure about the fresh epoxy penetrating the core material

Most ski cores being wood, it absolutely penetrates. Actually the front and back of the hole will be end grain and accept more than sides.

[XXX-er]

So wouldn't epoxy penetrate a shitty core > it would penetrate a good hard core and WTF is a good core vs a shitty core?

[Muggydude]

Well I can tell you the difference between the cores on the Rossi super 7s I drilled for inserts this season compared to the Praxis and ON3P cores I drilled was pretty surprising. Rossi core is practically crumbling/splintering away, not so with the others.

Though overall I don't think the Rossi is neccesarilly a "shitty core" but definitely not the same quality of materials. Including the topsheet layers as well

[galibier_numero_un]

Of course, you're right, but without this obsession, we'd have to start thinking about climbing, mountain biking etc., this time of year

Or skiing, which we plan to do this weekend and the next and the next. That, and I mounted two pairs of friends' touring skis yesterday, tapped + epoxy.

You are correct, sir! I was trying to be humble and not rub our brethren in California's noses in the dirt.

... Thom

[GeezerSteve]

Greg does not suggest that epoxy does not soak into the core material. He is merely saying that he thinks that it's not enhanced by tapping.

[gregL]

Greg does not suggest that epoxy does not soak into the core material.

Well, I doubt it. I think most epoxies are too viscous to be absorbed by most hardwoods used in ski cores. Less dense woods like Paulownia and balsa, who knows. I'm just saying I think you derive the most benefit in terms of pullout resistance from having more contact between screw threads and hole threads in the glass, carbon, titanal and resin laminate areas of the ski and less radial stress around the hole doesn't hurt either.

[Muggydude]

The epoxy most certainly soaks the core. When I was drilling my praxis skis for inserts I used 72 hour epoxy (forget the brand. It's in an orange pouch). The epoxy from one hole would ooze into other holes 15mm away when I'd install an insert. At first I thought I was dripping the epoxy in by accident before I figure it out. According to Praxis' website the binding area is hard maple.

And I was not using a lot of excess epoxy. Maybe a tad much but not overly

[Spyderjon]

The epoxy most certainly soaks the core. When I was drilling my praxis skis.... the epoxy from one hole would ooze into other holes 15mm away when I'd install an insert....

I've installed well over 1500 sets of inserts & in a decent core the epoxy won't migrate 1.5mm let alone 15mm! The only noticeable way epoxy will migrate is through gaps/cavities in the core. I've only installed a few sets on inserts in Praxis skis & the last thing I'd describe their cores as would be "hard maple".

[Muggydude]

Allow me to correct myself after thinking back a bit. It didn't happen on all the holes, I think mainly on some of them which were closer together, maybe 130mm (and that's center to center). So not actually 15mm, probably more like 6 or 7?
But it did indeed travel through the core that far, on more than one occasion and ski. The epoxy starts out pretty thin?


And no idea what exactly the type of wood is in the cores directly underfoot. Whatever it is, it makes a great ski

[RockinB]

Pretty sure Praxis finger joints maple stringers underfoot for solid binding rentention. I don't see any way that epoxy could migrate that far, maybe a mm but not 15. Epoxy does penetrate wood, some types more than others.

[tuco]

Less penetration from hardwood to softwood is kinda stating the obvious, but it will penetrate the hardwood. I wasn't suggesting complete saturation, that is why I believe the syringe to be overkill, only so much will be absorbed and the rest will come out the top of the hole. Under that same hardwood theory, I think you'll get less penetration into the tapped hole because when you ran the tap in there, you just compressed the fibers. Best thing to do for penetration would be to heat the ski(thus reducing viscosity when epoxy contacts the materials) before epoxying holes, the cooling ski will draw the epoxy deeper into the wood. The main reason for tapping metal skis is so the metal sheet doesn;t climb the threads of the screw and pull off the laminate(not saying tapping your wood skis is a bad idea).
Gotta do what you feel comfie with though.

Muggy, no way your getting that kinda penetration, something else going on there along the lines of what spidey suggested

Holy fuck, this thread needs Hugh, you guys are goobers

[neck beard]

The epoxy most certainly soaks the core. When I was drilling my praxis skis for inserts I used 72 hour epoxy (forget the brand. It's in an orange pouch). The epoxy from one hole would ooze into other holes 15mm away when I'd install an insert.

dood, c'mon. Ooze through the fibers of the wood in a few minutes? I'm guessing you had a big void in the wood, a tunnel linking the drill holes.

[Muggydude]

Maybe... I don't know. I'll see what happens with the next two pairs of skis I do.

It's possible there was something wrong with the core, but I doubt it? All the holes drilled solid, didn't seem like there was empty space. It was a while ago, who knows. Maybe I did drip epoxy in the holes by accident

[tuco]

It's possible there was something wrong with the core, but I doubt it?

I doubt it too.
Next time for super hyper focus powers, I suggest you don't stop after the first bowl is burned up.

[Muggydude]

Hey don't judge too hard. Mounting bindings is boring

[tuco]

it was more endorsement than criticism