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Greetings,<br>
<br>
I'm looking for a published standard for the number of threads that
are required to project beyond the end of the nut--especially
Nylocks.<br>
<br>
I've always recommended 1.5 to 3 threads extending beyond the nylon
insert, or the face of a metal nut. But when I tried to find an
actual standard to cite, there were none related to our industry and
only a few, rather specifically for "flanged joints: <b><big><span
style="color: rgb(51, 51, 51); font-family: Helvetica, Arial,
sans-serif; font-size: 12px; font-style: normal; font-variant:
normal; font-weight: normal; letter-spacing: normal;
line-height: 15.6000003814697px; orphans: auto; text-align:
left; text-indent: 0px; text-transform: none; white-space:
normal; widows: auto; word-spacing: 0px;
-webkit-text-stroke-width: 0px; display: inline !important;
float: none; background-color: rgb(255, 255, 255);">ASME
B31.3, 335.2.3<span class="Apple-converted-space"> .<br>
"</span></span></big></b><br>
<br>
This is the best I could find on the web:<br>
<small><small><br>
This is a difficult question to answer. Depending on your
application, the answer could be anywhere from 1/2 engagement,
up to having two full threads extend beyond the nut. Look at
these conflicting answers found in four separate technical
publications.<br>
<br>
Federal Highway Administration, “Guidelines for the
Installation, Inspection, Maintenance and Repair of Structural
Supports for Highway Signs, Luminaires and Traffic Signals.”
Section 16.3.1.2 Anchor Rods<br>
“Many times the rod is not long enough and the anchor nut is not
fully engaged. This in itself is not a serious deficiency as
long as at least three quarters of the nut is engaged.”<br>
<a class="moz-txt-link-freetext" href="http://wwwcf.fhwa.dot.gov/bridge/signinspection.pdf">http://wwwcf.fhwa.dot.gov/bridge/signinspection.pdf</a><br>
<br>
Industrial Fasteners Institute, Joe Greenslade, Director of
Engineering Technology.<br>
“How Many Threads Should Be Beyond The Nut?. The answer is: A
minimum of two thread pitches should extend beyond the top
surface of the nut.”<br>
<br>
RCSC (Research Council for Structural Connections) Specification
for Structural Joints Using ASTM A325 or A490 Bolts 2.3.2.
Geometry<br>
“Heavy-hex structural bolt dimensions shall meet the
requirements of ANSI/ASME B18.2.6. The bolt length used shall be
such that the end of the bolt extends beyond or is at least
flush with the outer face of the nut when properly installed.”<br>
<a class="moz-txt-link-freetext" href="http://www.boltcouncil.org/files/2009RCSCSpecification.pdf">http://www.boltcouncil.org/files/2009RCSCSpecification.pdf</a><br>
<br>
AISC Design Guide1 Page 10 Section 2.11.3<br>
“Often, when the anchor rod is short, it may be possible to
partially engage the nut. A conservative estimate of the
resulting nut strength can be made based on the percentage of
threads engaged, as long as at least half of the threads in the
nut are engaged.”<br>
<a class="moz-txt-link-freetext" href="http://www.aisc.org/store/p-1749-design-guide-1-base-plate-and-anchor-rod-design-second.aspx">http://www.aisc.org/store/p-1749-design-guide-1-base-plate-and-anchor-rod-design-second.aspx</a><br>
<br>
AISC Steel Construction Manual, 13th Edition, Section 14-10<br>
“Adequate thread engagement for anchor rods is identical to the
condition described in the RCSC Specification as adequate for
steel to steel structural joints using high strength bolts:
having the end of the [anchor rod] flush with or outside the
face of the nut”<br>
- See more at:
<a class="moz-txt-link-freetext" href="http://www.portlandbolt.com/faqs/recommendation-on-thread-engagement/#sthash.DV9RwF3K.dpuf">http://www.portlandbolt.com/faqs/recommendation-on-thread-engagement/#sthash.DV9RwF3K.dpuf</a></small></small><br>
<br>
I believe common practice in theatre is 1.5 to 3 threads, but I'm
not sure how much weight that carries with lawyers and such. What
say you all?<br>
<br>
Loren<br>
<br>
<pre class="moz-signature" cols="72">--
Professor Loren Philip Schreiber
Technical Director
School of Theatre, Television, and Film
San Diego State University
ETCP-T Certified Rigger #1095
CA Contractor License #966080</pre>
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