Binding mounting myths:

[Jethro]

Attachment 93487


Here's an Italian Forum with a member that tested the QuiverKillers versus screws.
I think it reads: Screws, 280 kg and QuiverKiller, 395 kg

Anyone have a heli-coil test link?

Thanks for posting that. I was regretting using Quiverkillers in my pricey new skis all day long before I read that. I knew I had seen similar numbers somewhere, which is why I went with inserts. Does anyone have any numbers for the smaller machine thread screws which go into the insert?

I do not know if this is pertinent, but whenever I pull a binding which I have somewhat liberally used epoxy on, there is alway a "mould" of the binding hole and sometimes the shape of the binding base in some epoxy overflow. Is there any chance this adds any shear resistance to the mount. It seems that if you had only a little screw looseness, the binding could wiggle back and forth on a micro level, kind of like the motion you would use to pull a large stake out of the ground. With a little side to side movement, that stake pulls straight out a lot easier. Just throwing that out there as an unproven hypothesis.

[GeezerSteve]

Okay, so to take things back to the beginning, why does it really matter? Seriously, how many people on here are actually ripping bindings out of skis on a regular basis. . . .

"Regular basis" is a bit lax for a standard. Dynafit toes rip out with enough frequency to concern me. A ripout on Day 3 of a 5 day trip can be a real bummer.

Thanks for posting that, Alpinord. Zeno and the Italian guys got ostensibly conflicting results. Core constituency and top sheet strength are big variables so a bigger sampling would be nice. And I'll second Terry's call for a helicoil pullout test. My money is on the helicoil.

[Mr. Toad]

Epoxy will keep the screws from rusting. I've used wood glue, water-proof wood glue, and the special binding screw glue that Tognar sells and all the screws rusted. OTOH, epoxy, Gorilla glue, and silicone caulking do not allow rust to form on screws. It matters most on tele bindings where only half the binding is screwed down and are subjects to a lot of stress.

[AlpiNord]

....... Zeno and the Italian guys got ostensibly conflicting results. Core constituency and top sheet strength are big variables so a bigger sampling would be nice........

The Zeno test was (2) for each per the chart (I do need to study that thread more). Since my Italian sucks, it's hard to say beyond (1) test each. I'd believe Snoli's ratings first (though Zeno's and the Italian's appear thorough and controlled), but with out a zillion such tests on different ski construction types it's not like we have a consensus on these tests to make absolute relative comparisons of insert tyoes versus screws.....but they are interesting and do give us some initial basis to use as a 'gauge'.

Regarding machine screws in the insert vs inserts or screws in skis, I can't imagine that the machine screw/insert combination is the weak link unless the screws themselves are substandard.

[GeezerSteve]

Regarding machine screws in the insert vs inserts or screws in skis, I can't imagine that the machine screw/insert combination is the weak link unless the screws themselves are substandard.

Right. IMV, the issue is wood screw thread (deeper/coarser thread pitch) vs. machine screw thread (shallower/finer pitch) biting the ski core, i.e., how well do QK/BF machine screw-based O.D. threads bite the ski core vs. wood screw threads (e.g., helicoil ski inserts). For those who may not have figured it out yet, QK/BL outside diameter (O.D.) is 5/16-18TPI machine screw thread, not a wood screw thread profile. Zeno comments about the EZ Lok insert he tested (8mm-1.25 O.D.) having threads that are not as deep as wood screw threads.

ETA: From Groov-Pin Corp re its wood-screw O.D. thread based inserts:

Wide thread spacing provides stronger threads for greater pull-out resistance.

Note Groov-Pin's pullout test results. GP also makes machine screw thread O.D.-based inserts.

[marshalolson]

1. jb (stick) weld is good for repairing salomon toe wing afds when they blow up every week
2. dps does NOT require epoxy. dps REQUIRES that you don't use water based wood glue (ie urethane, 2 part, 1 part, etc)

[AlpiNord]

Right. IMV, the issue is wood screw thread (deeper/coarser thread pitch) vs. machine screw thread (shallower/finer pitch) biting the ski core, i.e., how well do QK/BF machine screw-based O.D. threads bite the ski core vs. wood screw threads (e.g., helicoil ski inserts). For those who may not have figured it out yet, QK/BL outside diameter (O.D.) is 5/16-18TPI machine screw thread, not a wood screw thread profile. Zeno comments about the EZ Lok insert he tested (8mm-1.25 O.D.) having threads that are not as deep as wood screw threads.

ETA: From Groov-Pin Corp re its wood-screw O.D. thread based inserts: Note Groov-Pin's pullout test results. GP also makes machine screw thread O.D.-based inserts.

Well, per Snoli the fine threads are rated better than their coarse threads:


Brass Inserts 9 mm: pull-out resistance 268 kp, fine screw thread




Brass Inserts 9 mm: pull-out resistance 225 kp



QuiverKiller next to a Heli-Coil and Brass tap-in behind:

[GeezerSteve]

Does that top pic depict an insert with a knife thread, i.e., not a machine-screw thread? Looks like a knife thread to me, but pics can be deceiving. Several years ago I used some EZ Loks inserts with knife threads and they were bomber, although a bitch to install. A knife thread insert with a tap would be the ticket, IMV.

Also, those numbers relate to a pullout from what media? Maple? Plywood? Ski core? (if so, what ski?)

[marshalolson]

also, most 4-hole tele mounts typically are recommended with epoxy (notably bd 01's).

[GeezerSteve]

Russ Rainey insisted that Hammerheads be mounted with epoxy and supplied Hardman Bubble Pack expoxy with each set of bindings. Not sure if 22D is still doing that.

[jondrums]

I was really trying to ignore this thread, since I feel the initial post is quite misleading. But then it got interesting

When I was designing the threaded inserts, I was looking for a thread which had the minimum diamter, but still enough meat to support an M5 internal thread. I also wanted to maximize the thread penetration (major vs. minor diameter). And I felt it had to be a standard threadform, for which a bottoming tap is readily available.

Originally I was using 3/8-16 for its nice beefy threads, but then experimented with both M8x1.25 and 5/16-18. I really wanted to like the metric thread, so that both internal and external threads were metric. But, 5/16-18 threads have just a bit more thread penetration, and slightly coarser threads, so they won.

I feel that a custom threadform - more like the knife threads shown above is the ultimate. However I strongly believe that a self-tapping insert is a recipe for disaster - so then that would require a custom tap. I believe that 5/16-18 is the best all-around compromise for the M5 insert external thread.

[AlpiNord]

Jondrums
Can you provide the conversions?

What is the conversion from ft/lbs to kips to kg?

[GeezerSteve]

I also wanted to maximize the thread penetration (major vs. minor diameter). And I felt it had to be a standard threadform, for which a bottoming tap is readily available. * * * I feel that a custom threadform - more like the knife threads shown above is the ultimate. However I strongly believe that a self-tapping insert is a recipe for disaster - so then that would require a custom tap. I believe that 5/16-18 is the best all-around compromise for the M5 insert external thread.

That all makes sense. The major vs. minor diameter => more thread penetration is persuasive. Agree that a self-cutting thread would be a very bad idea. I speculated somewhere (TAY?) that the availability of stock taps contributed to your selection of O.D. thread.

[AlpiNord]

That all makes sense. The major vs. minor diameter => more thread penetration is persuasive. Agree that a self-cutting thread would be a very bad idea. I speculated somewhere (TAY?) that the availability of stock taps contributed to your selection of O.D. thread.

Does this mean that tapping binding screws in 3.5 holes is also a 'better idea'?

[GeezerSteve]

Well, we're talking about a larger diameter and different thread profile, although I'm uncertain how that changes things and, if so, to what extent. Zeno's tests, by extrapolation, would support tapping vs. no tapping whether or not there's a metal top sheet. I acknowledge that Zeno's tap vs. no tap test was limited to the machine screw based insert, but it so strongly militates in favor of tapping that an extrapolation seems warranted. Again, I would guess that the benefits of tapping vs. no tapping non-metal skis for AB screws would vary from ski core to ski core. On this issue, it looks like GregL is persuaded and is thus shopping for an ABS tap -- Greg, I suggest you give your biz to Slidewright

[AlpiNord]

I hear it all ways regarding tapping, inserts, screws and epoxy, so.........yes, no, maybe or depends, where are we regarding Binding Mounting Myths?

One thing I am absolutely sure about: Mount them on the top of the ski!

[GeezerSteve]

Hey Terry, does that Snoli pound-in brass insert expand when the ABS is screwed down?

[AlpiNord]

Hey Terry, does that Snoli pound-in brass insert expand when the ABS is screwed down?

Yes as do the nylon tap-ins. This is where the resistance comes from. Personally, I'd consider the nylons first. Smaller hole and less likely to fatigue and crack from what I recall.

EDIT:
Force Units:
v · d · e newton (SI unit) dyne kilogram-force, kilopond pound-force poundal
1 kp = 9.80665 N = 980665 dyn ≡ gn·(1 kg) ≈ 2.2046 lbF ≈ 70.932 pdl

[marshalolson]

those nylon pound in inserts flat out work.

i came up flat on a 50 footer with a hard enough impact to break a salomon 920 heel piece, and all 5 holes had plastic pound in inserts. not a single one had any issue.

[gregL]

Greg, I suggest you give your biz to Slidewright

I definitely will at some point, but I already have a tap and handle!

[131crew]

Many people around here pretend to be experts and enjoy hearing themselves talk.
This strikes me as one of the douchiest attempts.

Either provide the data to back everything up or get off your horse.

+1

Well stated.

[jondrums]

Does this mean that tapping binding screws in 3.5 holes is also a 'better idea'?

I happen to THINK so, but what's that worth?

[skimaxpower]

^^agreed. Tapping a 3.5/3.6mm hole means that less torque is required to install the screw. I find (in my experience) that this reduces the risk of over-torquing the screw and getting a spinner.

The screw-pull-out tests that I've seen do indicate a slightly reduced holding strength for screws installed this way. However, it's still way stronger than required to pass muster. IMHO, tapping all holes is the best way to avoid spinners when installing bindings.

(It's easier to get the glue in the tapped hole, too.)

[GeezerSteve]

Agree that it's easier to get glue or epoxy into a tapped hole. Also, it would seem that the glue/epoxy might have more opportunity to seep into the surrounding core if threads are cut rather than smashed.

The screw-pull-out tests that I've seen do indicate a slightly reduced holding strength for screws installed this way [i.e., tapped hole]

Do you have a linky? Zeno's test of the 8mm-1.25 insert indicated that tapping significantly enhanced pullout strength. As noted above, he didn't test ABS tapped vs. untapped.

[alTAos]

You have to take the pullout test numbers with a grain of salt. Even if you use the same ski core, the difference in properties from one area to the other could vary significantly depending on how they lay up the skis. 2 tests per each setup isn't close to enough to conclude anything even if you knew more about the ski. Just look at the epoxy numbers. Adding epoxy to a regular binding screw increased pullout by like 30% or something, whereas adding it to the inserts hurt the pullout strength. That doesn't add up. I think it would make more sense to do pullout tests on a synthetic material that was more consistent in properties and compare the numbers to that. It really doesn't matter what the number is, rather how it compares when tapping, epoxying, pilot hole size, etc.