bindings to board screws question

[bobbeck]

My Catek OS2s came with 12mm overalll lentgh screws with the original elastomer. I now have the D3 elastomer and longer 14 mm screws. I measured the depth of my inserts and I could use longer screws say 15-16mm without bottoming out. I have to tighten them several times in the season. My questions are, viz

1) should I use the longest screws possible?

2) should I use locktite red anerobic adhesive on the screws?

3) Is it normal for the screws to back out over time?

[bobdea]

My Catek OS2s came with 12mm overalll lentgh screws with the original elastomer. I now have the D3 elastomer and longer 14 mm screws. I measured the depth of my inserts and I could use longer screws say 15-16mm without bottoming out. I have to tighten them several times in the season. My questions are, viz

1) should I use the longest screws possible?

2) should I use locktite red anerobic adhesive on the screws?

3) Is it normal for the screws to back out over time?

1, no, just make sure you get four full turns

2, NOOOOOOOOOOOOOOOOOOO, locktite is bad for boards and red is considered permanant

3, yes, check your bindings every couple days out

[bjvircks]

Agree with spirit of bobdea's answers but not some facts.

1) do not use the longest screws. 4 threads min. engagement is good advice

2) DO NOT USE TRADITIONAL LOCTITE LIKE PRODUCTS. I'd suggest a threadlocker called 'vibratite'. It is dripped onto the screw thread which is then set aside and allowed to cure for a day. Then you use the screw. This gives you a plastic compound in the threads. The same screw can be reused a couple times (YMMV) without reapplying the locker. With locktite... single use only, then reapply.

3) what some consider to be screws 'backing out' is actually the system relaxing a bit over time. The technical term for this is creep or cold-flow. Yes, they need to be checked and re-tightened. But not because (most often) the screws have turned.

On avionics we specify certain torques to be applied to fasteners. When this is performed with calibrated tools and skilled operators the results are highly repeatable. However, when an assembly is properly torqued, set aside for a couple days, and then torqued again... the screws can be turned somemore before reaching the prescribed torque again. Some argued that this was evidence of improper initial assy (claimed operators were not reaching specified torque) until we proved otherwise by having the disbelievers assemble the parts themselves, lock the assembly and calibrated tool they used in their desk. 2 days later they could get another 1/4 turn before reaching torque limit. This was aluminum to aluminum with helicoil inserts. Just think how much creep occurs when rubber gaskets flow under pressure and metal inserts in the wood core move a little.