alpinelakespilot2000 said:
You seem to be missing my point. I am absolutely and genuinely interested in knowing what the actual number is that we must add for a nyloc nut. I know my rule of thumb is not based on any official source of information and I stated that up front in my posts. That's why I'm trying to have somebody correct me. Can someone point me to a chart that indicates what values we must add for a given fastener? I hear a lot of people saying add a certain amount for the friction factor, but no one has yet (to my knowledge) pointed ot an official source that says how much to add and/or how to calculate that number. If you read up further in this thread, and then do a search of the other threads that deal with torque and you will see a LOT of confusion on this topic--hence my request for the amount from an official source. I just read through chapter 7 of 4313-1B last night and couldn't find anything definitive, except that chart 7-1 (in that same chapter) indicates that a AN3 bolt-365 nut combination requires 20-25 in.lb. of torque.
Any help?
Steve:
I dont' think I missed your point. I gave you a direct example where 2, seemingly identical nuts, from the same manufacturer and batch revealed drag values that were 43% different from each other. The variance was greater the than 2.5 pound value you mentioned.
Here's the reference that supports each point I made (Q is an accepted abbreviation for the word torque):
AC43.13-1B Paragraph 7-40.
Subparagraph a. Calibrate q-wrench every 12 months or immediately if abused.
Subparagraph b. Clean and dry threads.
Subparagraph c. Check run-on Q with each torgue event. Also Q from nut if possible. (If you torque from head out of necessity, you will notice the run-on torque or drag can be significantly higher. That is an observation from 3 decades of experience in aircraft maintenance.)
Subparagraph d. Add the friction drag to the desired Q to arrive at the wrench setting.
Subparagraph e. Apply a smooth, even pull. Again, I have first hand experience as an aircraft manufacturing and maintenance quality inspector that a sharp, uneven pull can cause a wrench to click at a reduced load. I've seen them click when the actual, on-the-nut, torque was 50% lower than what the release click or indicator said.
Subparagraph f. How to torque castelated nuts using the minimum and maximum values.
Subparagraph g. Capscrews or bolt heads. Highlights the need to MEASURE AND ADD drag or run-on values to achieve the REAL, no-s*** torque being applied to the threads.
Subparagraph h. How to adjust wrench settings if using adapters.
In all this, there is nothing mentioned about rules-of-thumb, guesses or establishing drag factors by hardware categories. As I said, run-on torque is determined each time you grasp a torque wrench. It's just the way torquing is done. Not following these rules is tightening", not "torquing".
In my work in aircraft and engine shops, I've not seen many nuts or bolts tightened without a torque wrench. Situations that effect safety-of-flight or that may injure personnel are SPECIFICALLY FLAGGED on assembly sheets to require a quality inspector's presence for personnal verification and sign-off to attest to that the torque was done correctly. Did it this way as a working mechanic, a quality inspector and as a manager of maintenace shops.
Those that say aircraft manufacturers and repair shops don't torque, and that attest to having first hand knowledge to the fact, are, in my opinion, owning up to working at substandard shops. Manufacturing and maintenance is no different from other human activities in that, if left alone, we gravitate to entropic processes. Safety requires energy.
Official source pointed out.
Jekyll
