What's the boron content of 10B30?
I note that ISO 898-1 limits the boron content of material used to fabricate property class 10.9 fasteners to .003% (.005% provided that "non-effective boron is controlled by addition of titanium and/or aluminum").
Does "equivalency" require grademarking (marking with "10.9") or representing/selling the parts as meeting Grade 10.9? If so, manufacturing bolts to anything less than the full requirments of the ISO standard is a SEROIUS crime punishable by both civil and criminal penalties per the Fastener...
Lurchalot:
Re-read midsidenode's original post:
A delayed failure mecahanism is at work here, most likely hydrogen embrittlement as suggested above. This is not a "simple" overtorque failure.
From the FRR Briefing Transcript:
QUESTIONER: Traci Watson, USA Today, for Wayne Hale.
First, a clarification. When you talked about the bolts that had only two-thirds of the thread or one-and-a-half threads engaged, was that on the KU antenna, or was that somewhere else? I missed that.
MR...
Based on the available information, I wouldn’t personally characterize anything about this situation as "perfectly adequate" (an oxymoron?).
While it was apparently "adequate" for 25 flights (based solely on the absence of a catastrophic failure), what about the 26th? The "it worked last time"...
Wayne Hale (http://www.nasa.gov/centers/kennedy/about/biographies/hale.html), excerpted from the Post Flight Readiness Review Briefing Transcript (http://www.nasa.gov/pdf/154909main_postFRRtranscript%20_2.pdf);
"Some 25 or 30 years ago, a mistake was made in the design of this particular...
Like MMPDS-02, ESDU00932 isn't free either: http://engineers.ihs.com/engineering/newsletters/esdu/esdu-issue08-06.jsp and http://www.esdu.com/cgi-bin/ps.pl?sess=unlicensed_1060801190352snh&t=ser&p=mmdh
Couple of reason why not:
"Normal" bolts are thread rolled, for cost and other reasons. The asymmetrical buttress thread does not lend itself to thread rolling with acceptable tool life or without developing unacceptable defects. "Cut" threads both cost more to make in large quantities and...
While a higher strength insert material may minimize insert stripping at the present bolt thread length of engagement and torque level, check to make sure that that your test guys are using bolts of adequate length to fully engage the internal insert threads when installed in your stackup(s)...
A cutting tap does not cut/form the minor diameter, just the flank angles and major diameter. The pre-tap hole diameter is not a "pilot" hole, it is critical and must meet the modified minor diameter requirements of the UNJ thread prior to tapping.
Don't think I've ever seen roll taps...
A literature search (and/or a little bit of pondering) will confirm that thread flank angle has a direct influence on resistance to loosening in a vibratory environment.
I note that SPS lists Inconel 718, 17-4 PH and Titanium as material options on page three of their document I linked above (first link).
But I'll hazard to guess these may be vendor parts numbers and/or "specials" that will have limited sources and availability (and higher costs/leadtimes)...
Key-locking threaded inserts manufactured from A-286 are widely used in aerospace under NAS1395 and MS51830 part numbers. A-286 is a highly "durable" material...
http://www.spstech.com/aero/prod_lit/insert_brochure.pdf...
