What is Effect of Thread Class on Torque & Preload?
What is Effect of Thread Class on Torque & Preload?
(OP)
I am wondering what effect thread class has on the ability to effect a preload (accurately) in a machine screw, as indicated indirectly by torque. Specifically, I am looking at several 1" studs from a flange joint; the sloppiness of the nuts prompted my query.
One thought I had is that possibly individual threads have less mutual support, resulting in more local deformation of threads. Of course initial tightening will be somewhat easier when using fingers.
Any thoughts/knowledge on this?
One thought I had is that possibly individual threads have less mutual support, resulting in more local deformation of threads. Of course initial tightening will be somewhat easier when using fingers.
Any thoughts/knowledge on this?





RE: What is Effect of Thread Class on Torque & Preload?
RE: What is Effect of Thread Class on Torque & Preload?
I found that book, but where do I look?
RE: What is Effect of Thread Class on Torque & Preload?
http://sites.google.com/site/olivertestingandconsulting/home/fastener-articles
http://muhendisizbiz.net/uploadlar/12216/three-dimensional_finite_element_analysis_of_threa.pdf
http://www.ewp.rpi.edu/hartford/~petrab/project/references/ref4.pdf?bcsi_scan_20bca982f500602a=0&bcsi_scan_filename=ref4.pdf
https://www.faa.gov/library/reports/media/FASTENER_AUDIT_REPORT.pdf
RE: What is Effect of Thread Class on Torque & Preload?
If the "sloppy" threads still meet a reasonable dimensional standard I would not expect a de-rate.
Would New nuts fix it ?
Note that the tap drill size could influence the " % of thread (height)" and be indetectable as "slop."
http://www.boltscience.com/pages/strength.htm
"Studies have shown that for threaded assemblies of usual proportions, tap-drill size is relatively unimportant so long as the percentage of thread height is greater than 60%."
Here's a case (formed threads) when the threads checked fine with gages, but had very weak threads.
http://machinedesign.com/article/internal-thread-strip-out-tests-yield-surprising-results-0113