Loctite on bolts - effect on torque values?

Messages
24,453
Location
CA
I understand that if you use anti-seize or some kind of lubricant, you need to reduce the recommended torque values for a bolt by about 20%. However, if you use Loctite, do you need to do the same? I ask because Loctite is not a slick, greasy lubricant like anti-seize is. It is simply wet, and you are only putting a few drops on several threads (usually). For instance, if you use Loctite on the brake caliper mounting bracket bolts, would it be prudent to reduce the torque spec by 20%? Thanks.
 
Messages
169
Location
Ontario Canada
You may see a lot of different opinions on this. However, Loctite suggests that there be no change in "on-torque" values. So, torque to dry spec for all Loctite Purple, Blue, Red...
 
Messages
26,453
Location
MA, Mittelfranken.de
This is a question i have had for long time also. I cant find a concrete answer. I was also of the understanding that it didn't effect the torque value. When GM started recommending it on the upper plastic intakes on 3800 GEN II engines they didn't change the torque spec. When you tried the same torque there was no way, the bolt would snap or you could put a crack in the plastic bolt boss. I tried the spec torque on clean dry threads and noted the torque angle at 10lb from the 5lb setting. With the Loctite it was much more. 20% sounds about right as at 8lb i had the same angle with the loctite applied. This was totally unscientific, just a hack measurement but yes there was a difference. You may want to try the same and see what you get. I know the OEM bolts with pre coated dry thread locker there is no measurable difference.
 
Messages
2,287
Location
Canada
Originally Posted By: The Critic
For instance, if you use Loctite on the brake caliper mounting bracket bolts, would it be prudent to reduce the torque spec by 20%?
Do not change the torque figures. I have never personally come across any brake assembly that required Loctite. Why are you wanting to use it?
 
Messages
4,021
Location
New England
Originally Posted By: Tegger
Originally Posted By: The Critic
For instance, if you use Loctite on the brake caliper mounting bracket bolts, would it be prudent to reduce the torque spec by 20%?
Do not change the torque figures. I have never personally come across any brake assembly that required Loctite. Why are you wanting to use it?
The brake caliper mounting bracket bolts (if what Critic is describing is what I think it is) often have Loctite on them. The other side of that though, is I don't know if I've paid attention to a torque spec on those, I always just sock them down.
 
Originally Posted By: Tegger
Originally Posted By: The Critic
For instance, if you use Loctite on the brake caliper mounting bracket bolts, would it be prudent to reduce the torque spec by 20%?
Do not change the torque figures. I have never personally come across any brake assembly that required Loctite. Why are you wanting to use it?
+2
 
Originally Posted By: Tegger
Originally Posted By: The Critic
For instance, if you use Loctite on the brake caliper mounting bracket bolts, would it be prudent to reduce the torque spec by 20%?
Do not change the torque figures. I have never personally come across any brake assembly that required Loctite. Why are you wanting to use it?
I know that VW uses thread locker not only on the bracket bolts, but also on caliper sliding pins.
 
Messages
26,453
Location
MA, Mittelfranken.de
Quote:
Benefits of Loctite® Threadlockers •• Lock nuts and bolts against vibration and thermal expansion •• Seal against corrosion and leakage •• Reduce inventory costs •• Suitable for all shapes and sizes of fasteners •• Act as a thread lubricant ••Maintain critical adjustments of the assembly •• No on-torque adjustments needed •• High chemical resistance
Its the thread lubricant part that i wonder about. I have always understood torque figures were for clean dry threads unless otherwise specified.
Quote:
No on-torque adjustments needed
I cant figure this out. Do they mean you don't need to adjust the torque setting or you don't need to re torque?
 
Messages
3,496
Location
VA
I always thought torque specs were for clean & lightly lubricated threads, NOT dry... Anyway that's how I've torqued mine for the last 40 years or so, never had a issue...
 
Messages
1,587
Location
USA
Blue loctite on every nut and bolt I mess with, especially in the wheel well. This saves so much hastle with seized rusty threads when you live in the rust belt. No change in torque either.
 
Messages
19,479
Location
Chicago Area
That reduced 20% torque thing is not an absolute, for sure. This varies widely for a bunch of reasons. As someone pointed out somewhere in BITOG, on the threads is way different that also being on the mating surface. Mating surface lube really slicks thing up. With a lubricant like Locktite on the threads, I certainly would not OVER torque any parts! Go 5% under and sleep well.
 
Messages
26,453
Location
MA, Mittelfranken.de
I just checked a bunch of manuals and they spec clean dry threads.
Quote:
Torque nuts & bolts with clean and dry threads unless otherwise specified in the maintenance manual. Do not lubricate nut or bolt threads unless otherwise specified in the maintenance manual.
This is a decent chart. I guess the best way is to find out what the FSM recommends wet/dry and use their torque specs. 20-30% for lube thread looks right though. looking at 1/4" bolt (i was torquing a 6mm) my angle observation was very close. http://raskcycle.com/techtip/webdoc14.html
 
Messages
2,287
Location
Canada
Originally Posted By: Gotch
No such heading as "Loctite Advantages". But I do find "Loctite Benefits", none of which apply to passenger-car brakes as serviced by the public. The wording of that section suggests that it's aimed at a production environment, not at a grease-monkey doing a one-off of a passenger-car's brakes. I've used Loctite in many circumstance, but have NEVER seen it specified or even recommended for ANY automotive brakes I've ever encountered. If VW uses thread-locker on their brake components, then all I can say is that they're doing something impractical. Or their manufacturing tolerances are really, really sloppy, and this ain't your grandfather's VW.
 
Messages
4,021
Location
New England
Again, GM specs it for the caliper mounting bolt brackets. You could make the argument that it's not technically a brake component, but it is the subject of this thread so it is relevant.
 
Messages
2
Location
South Carolina
WHOA HOSS! I was checking for HOW MUCH i needed to reduce torque when using Loctite and I came across this thread on my search. I was thinking it was 30%. I joined your forum just to comment on this thread, I was horrified at all the misinformation on here - the misconception of what lubrication even is. If you think it has to be grease or oil to be lubrication, think again, folks. WATER is a lubricant! Granted it ain't very good, but it is. Gasoline? Lubricant. Yeppirreedoodle, sir. Loctite, before it dries, is a rather good lubricant. So you think you can just tighten those screws into your aluminum case at the same torque w/o worry when you use Loctite? Shyaaaaaa, know what? yer gonna STRIP 'EM! I work on aluminum engines all the time, I sell Yamaha snowmobile engines for aircraft conversion (at 150 HP and only 120 lbs , 4-cycle and water cooled how can ya go wrong?), special clutches, gearboxes and adapter kits. There have been times when I have forgotten to reduce torque when adding loctite to the threads, and I have wound up having to Helicoil the [censored] things when I did so. EVEN LOCTITE ENGINEERS TELL YA TO REDUCE TORQUE 20%, so where do you guys come up with this nonsense that you supposedly don't need to reduce torque because? Is it because it ain't 5W-20 and therefore it ain't lube??? And it ain't one or two of you, it's an entire THREAD FULL OF MISINFORMATION! Loctite, when still wet, is a lubricant on the threads and YOU MUST REDUCE TORQUE 20% when using it. Next, try this: Use a 3/8" drive ratchet for those little M6 and similar small screws threaded into cases to secure covers, etc. Hold the wrench close to the socket, not way out at the end. As you tighten, you can feel the resistance to the wrench increase as you go past snug. Keep turning slowly, until you feel it is as far as you want to go. Sometimes the resistance will even "hitch" a bit. Now stick a torque wrench on it, note the position of the handle (1 o'clock, 6 o'clock, etc) and then loosen the screw. Then torque it back to the same location and figure out how much torque that is and compare to spec. Once you get your "feel" down and get it to compare to actual spec torque values, go with it. A torque wrench is this HUMONGOUS thing that makes it nearly impossible to FEEL what is happening with smaller screws and if you can't feel the difference you are bound to strip threads. What's important is to be able to tell when you are nearing the point of stripping threads. When you use a SMALL, suitable wrench handle you WILL be able to tell when you keep advancing the wrench and yet the resistance fails to increase any more. THAT IS WHEN YOU STOP TURNING THE WRENCH, of course - cuz otherwise that is when you are going to strip those little threads. AGAIN - REDUCE TORQUE 20% when using Loctite. Ya know what? It is nearly impossible to get threads dry when tearing stuff down and putting it back together. That is why, unless you can get it absolutely clean and dry, it is far easier to just use the Loctite and suitable REDUCED torque specs that go along with it. I'm outta here guys. But check out our website at www.MohawkAeroCraft.com, and our Facebook group "Yamaha Aircraft Engines" Yours truely, GT Mills Columbia, SC This is one of my 3 gyroplanes, with the Yamaha 150 HP conversion. Here it is shown fitted with a long range fuel tank in place of the rear seat, which gives it a range of 4 hours at 80 MPH, 320 miles. With the rear seat in place it has a range or 250 miles. Gyrocopters/gyroplanes provide all the fun of a helicopter at a tiny fraction of the cost. They are far more nimble and fun than a fixed-wing plane, and in the event of power loss you simply glide down to the ground, pull all the way back on the stick to stop it and float down the last foot or two with zero forward speed. With a fixed wing airplane you have to carry that 50-60 MPH glide speed when you land with no way to slow down or stop like this, and unless you are in a nice, clear open field or back at the airport that is what causes all the damages and injury. Gyros are the safest thing in the air. Lessons are $150-$180 per hour, which includes another hour of ground training, the rent of the aircraft and fuel. gyros in good, flying condition can be purchase for as little as $6000, with high-end models selling for $65,000 - $150,000. Feel free to contact me for more info, where to get free rides, and $40 introductory lessons - to see if this is the thing for you! We have access to clubs and certified instructors all over the USA, and abroad! Write to [email protected]
 
Messages
1,546
Location
iowa
^^^^Excellent post Aero! Totally agree that developing a feel for the bolt clamping, is better than a torque wrench many times.
 
Last edited:
Messages
17,501
Location
Clovis, CA
I never reduce torque values when using Loctite, anti-zeize, or oil. The torque specifications were intended for free, easy turning fasteners.
 
Top