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<DIV><FONT face=Arial size=2>Nothing is ever simple. fatigue life of steel is
directly proportional to tensile strength. Fatigue life is also dependent on
surface residual stress. So the best thing you could use is a hardened bolt with
threads rolled after heat treat (good compressive residual stresses). Like
Dean says, finer pitch has a larger root diameter. The trouble is, the cheap
hardware stuff we buy is generally rolled before heat treat, so it has crappy
residual stress (tensile on the surface). So what I try to do is go large (6-32
or 6-40) and try to find a bolt with a long unthreaded length (the threads
act like stress concentrators).</FONT></DIV>
<DIV><FONT face=Arial size=2>Jeff</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=billglaze@triad.rr.com href="mailto:billglaze@triad.rr.com">Bill
Glaze</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, February 14, 2005 12:47
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: 4-40 or 6-32 control
arms?</DIV>
<DIV><BR></DIV>ED:<BR>A few years ago, there was quite a dialogue about
this. One of the participants was Dick Hanson, a man highly respected in
Pattern and other disciplines. The subject came up about a couple of
individuals who were looking for extra strength on aileron and elevator
actuator bolts. Dick said, specifically, do not get hardened bolts or
anything exotic. He said such material won't stand up under vibration
nearly as well as common rolled thread material, or, for that matter, some of
the standard Home Depot or Lowe's bolts right off the peg board. He said
that the ductility is what prolonged their life; that he had never had one
break. I believed him then, and still do.<BR><BR>Bill Glaze<BR><BR><A
class=moz-txt-link-abbreviated
href="mailto:Rcmaster199@aol.com">Rcmaster199@aol.com</A> wrote:
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<DIV>
<DIV>In a message dated 2/14/2005 12:22:29 AM Eastern Standard Time, <A
class=moz-txt-link-abbreviated
href="mailto:ed_alt@hotmail.com">ed_alt@hotmail.com</A> writes:</DIV>
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<DIV>I've been using 6-32 bolts to make the control horn arms for my 2M
setups so far. It seems like that might be overkill and that 4-40
would suffice. Is it OK to go lighter like this?</DIV>
<DIV> </DIV>
<DIV>Thanks</DIV>
<DIV>Ed A.</DIV></FONT></BLOCKQUOTE></DIV>
<DIV>Ed I wouldn't do that especially on ailerons. I have had 4-40's snap
off like twigs on 90 sized models before. The vibration kills them.</DIV>
<DIV> </DIV>
<DIV>Matt</DIV></FONT></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>