Wicking grade Loctite

[SDHNTR]

Anybody ever used wicking Loctite on scope mount fasteners? I was thinking about this, with the debate over whether Loctite on threads changes torque values meaningfully (FWIW, I do not think it’s a big deal and I’ve never had a problem personally) I thought why not torque dry, and then apply a couple drops of wicking Loctite. Best of both worlds? Anyone done this?

 

[4th_point]

Green wicking variety works really well in my experience, but not easily removed like blue. Obviously depends on application.

If you contact Loctite technical people about wet vs dry torque, they will tell you that you need to perform your own study. It does have an effect no matter what the marketing people say.

Some people swear up and down that thread locker doesn't have an effect. I get it. May not matter for certain applications, but...

 

[SDHNTR]

Green wicking variety works really well in my experience, but not easily removed like blue. Obviously depends on application.

If you contact Loctite technical people about wet vs dry torque, they will tell you that you need to perform your own study. It does have an effect no matter what the marketing people say.

Some people swear up and down that thread locker doesn't have an effect. I get it. May not matter for certain applications, but...

I’ve called and talked to them and the conclusion was that it didn’t affect torque values enough to matter in this application and with the inch pounds involved. But that also seems to be a matter of opinion, and the answer one might receive might be entirely dependent on who picks up the phone.

Which is why I was thinking of an alternative to rule out any opinion or interpretation. I’m aware of the green wicking stuff, do they make a low strength (blue equivalent) wicking option?

 

[Wrench]

The torque answer can be found in machinery handbook and there's a couple of value changes on coefficient of friction iirc.

As for wicking, I just use nail polish and visually inspect. I get more piece of mind seeing vs hoping the locktite held.

 

[4th_point]

I’m aware of the green wicking stuff, do they make a low strength (blue equivalent) wicking option?

I think Loctite just has the one. There are other brands for low strength but I have not used any of those.

 

[Fowl Play]

I have used it for other purposes. Its locking ability is not as good as standard loctite applied to male and female threads. You would still have to clean and degrease the threads well and yet would still wind up with a less robust connection.

 

[Choupique]

whether Loctite on threads changes torque values meaningfully

Of course it depends. Generally action holes and base screws are never degreased properly for it to matter.

Threadlocker does change torque values vs true dry threads. I wouldn't bother adjusting for this purpose though.

 

[RockAndSage]

OP, I think your idea of torquing dry and then adding some sort of appropriate adhesive is the safest approach, and a good idea. Whether it's with a wicking variant or not. Wet torque specs can cause anywhere from 15% to 40% additional clamping force on something like scope rings, IIRC, depending on the lubrication properties of the liquid in question and the surface areas involved. Thinner and less viscous will usually lubricate less, but not always.

This is actually an issue of increasing importance as scopes get lighter and their tube walls get thinner. It's disturbingly easy to over-torque on something like a new Swaro or Leupold, and end up causing tracking issues, or a wandering zero, as the rings crushing into the tube alter the dynamics of the erector. It's not as much of an issue with the stouter Nightforce or Trijicons, and Tangent Theta actually specifies 25in/lbs of torque, while Leupold is 15, IIRC. It's pretty easy to inadvertently stack additional torque with lube on fasteners and, say, a torque wrench a little out of spec from being left off zero.

 

[SDHNTR]

Right. I use mostly NF and Triji. In my mind I’ll take my chances with an extra inch pound or two over the risk of screws shooting loose and a scope slipping. I’ve added a drop or two for years and have never crushed a scope tube or bound up an erector. And I used to own a bunch of Swaro POS’s!

Additionally, I’ve seen that 15-40% variance number bandied about like it’s gospel. Where did that range of numbers originate?

I think I’m gonna buy some wicking green and try it on some spare rings I’ve got laying around.

 

[Choupique]

Bolt torque is kind of voodoo dark magic anyway. It's a super un-precise way to estimate bolt tension but it is the easiest thing to measure.

If we really cared a whole lot about this, we would be using studs and tensioning them or measuring stretch. Just degrease everything the best you can, goop loctite on it, and torque to whatever the suppliers spec is and go shoot.

One of these days all these parts and scopes and stuff will start coming with dowel pins so we can all quit worrying about this.

 

[eoperator]

I have been using vibra tite the past couple years. This stuff does not completely dry hard, it stays in a kinda hard gel consistency that can be reused. Vibra tite will most likely change torque values so it will not solve that problem for you.

 

[RockAndSage]

Right. I use mostly NF and Triji. In my mind I’ll take my chances with an extra inch pound or two over the risk of screws shooting loose and a scope slipping. I’ve added a drop or two for years and have never crushed a scope tube or bound up an erector. And I used to own a bunch of Swaro POS’s!

Additionally, I’ve seen that 15-40% variance number bandied about like it’s gospel. Where did that range of numbers originate?

I think I’m gonna buy some wicking green and try it on some spare rings I’ve got laying around.

Sounds like you've got nothing to loose and aren't risking anything by dry-torquing and then adding a drop or so of one of the right loctite. You'll want to be careful with selection though, as there are different types of "green loctite" - the 200 series green are essentially ultra-permanent, with heat and/or special chemicals needed to dissolve them. The 600 series greens might be more of what you're thinking, as they're retaining compounds generally meant for bearings and similar things. Which, I've seen some people use in the gun world for bedding AR barrels, scope rings, and cylindrical items in general. It will act a bit more like clear nail polish when you go to remove it, with any excess flaking off fairly easily with your fingernail, but still retaining the position of the cylindrical item you're trying to keep in place.

Regarding the 15%-40% number, it's a good general rule of thumb that's mostly meant to be a cautionary word to the wise, to cause them to think twice about how much torque they add, and to get more details. Kind of like "measure twice before cutting once". It's that broad of a range because of the variables involved in torquing fasteners. Thread pitch, surface areas, tolerances, and the various types of coefficients of friction involved with the surfaces (materials, inherent smoothness, dynamic vs static, etc) each make a different impact, as do the lubrication properties of any fluid involved. If you want extreme details, you can find tables that go into it in-depth in various manuals and handbooks used by machinists and similar highly-skilled trades, like this one.

 

[4th_point]

If we really cared a whole lot about this, we would be using studs and tensioning them or measuring stretch. Just degrease everything the best you can, goop loctite on it, and torque to whatever the suppliers spec is and go shoot.

Lock wire or safety cable!

 

[4th_point]

You'll want to be careful with selection though, as there are different types of "green loctite" - the 200 series green are essentially ultra-permanent, with heat and/or special chemicals needed to dissolve them.

I have used green penetrating a few times where I swear it was harder to remove than any red semi-permanent. Maybe it got into the nooks a little better.

 

[4th_point]

For the record, I don't sweat the use of blue low strength on things like bases. But I generally don't use any thread locker on caps. Except for one brand of ringmount!

If people have a method that works for them, I'm cool with that. The blanket statements of thread locker not affecting clamp load is what can be misleading to the casual reader. Just proceed with caution is all!

 

[SDHNTR]

I have used green penetrating a few times where I swear it was harder to remove than any red semi-permanent. Maybe it got into the nooks a little better.

Interesting. 290 green says medium strength, just like they claim blue 242/243 is also medium strength. I ordered a tube. I'll try it and will report back with my findings.

 

[Fowl Play]

Lock wire or safety cable!

I’d actually like to see shear pins used… take friction out of the equation.

All this talk is making me want to sit down and calculate what an appropriate torque value actually should be with Loctite. Sick as a dog now, but maybe later. Instantaneous g load on a scope is likely around 4-500g. For a 25oz scope that’s about 800lbs of force axially on the scope. Coefficient of friction between hard anodized aluminum pieces is probably .2 — means you’d need to generate approx 4,000 lbs of preload to have friction restrain it. Lots of assumptions on the g value though…

 

[SDHNTR]

Well I tried it with Loctite 290. I think might have found my new method.

Took a set of old Leupold rings I had in the boneyard box. Degreased thoroughly. Torqued them onto a lapping bar at 20 inch pounds. Put a couple drops of green 290 on the bottom side on the ring half, since that is where the threads are, let set 20 min, wiped off excess, and left sitting upside down for 24 hrs.

Just unscrewed it. Some minimal effort required, maybe just a touch more subjective force required to unscrew than standard blue loctite, but nothing difficult. It definitely wicked into the threads nicely.

Next up, I’m going to try another set of 4 screw rings torqued to 25#.

 

[4th_point]

Good deal.

Can you measure breakaway torque with your wrench?

 

[SDHNTR]

Good deal.

Can you measure breakaway torque with your wrench?

Yes, I can, and will, but I don’t think that’s as accurate of a measurement as initial torque setting. Anyway, I just assembled a set a few minutes ago. Will report back after 24hrs cure time.