X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Sat, 07 Oct 2006 11:49:48 -0400 Message-ID: X-Original-Return-Path: Received: from imo-d04.mx.aol.com ([205.188.157.36] verified) by logan.com (CommuniGate Pro SMTP 5.1c.5) with ESMTP id 1447988 for lml@lancaironline.net; Sat, 07 Oct 2006 11:00:17 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.157.36; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-d04.mx.aol.com (mail_out_v38_r7.6.) id q.c54.48523d6 (41809) for ; Sat, 7 Oct 2006 10:59:53 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Sat, 7 Oct 2006 10:59:52 EDT Subject: Re: [LML] Torque specs X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1160233192" X-Mailer: 9.0 Security Edition for Windows sub 5326 X-Spam-Flag: NO -------------------------------1160233192 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 10/5/2006 9:26:12 P.M. Central Daylight Time, leighton@teleport.com writes: The recent discussions about proper torque on such things as engine mount bolts reminds me that over the years I have heard from several normally reliable sources that using a torque wrench on locking nuts (either plastic or all metal) is not only a waste of time but possibly even a bad idea. The logic is that because of the built in interference of the nut either a lower than desired reading will be read or upon approaching the desired torque the nut will "slip" and result in higher than desired torque. It's been pointed out that truly torque-critical items, like connecting rod bolts and case half connecting bolts never use locking nuts. In other words, if the torque is really important don't use lock nuts. I am curious what others on the list might have to say about this. I am not an engineer, nor do I play one on TV, but I've been using nuts and bolts since way back in the Erector Set days and have absorbed "do" and "don't do" advice from people whose expertise I respect, including the above observations on torquing fasteners. I probably won't change what's worked well for me over the decades but perhaps someone has some compelling argument to the contrary, or perhaps confirm what I've heard. The floor is open. Leighton, Proper torque........Hmmmm... Since I am a simple minded person, all I know is that there are many bolt-type fasteners that must be tight enough. Ignoring my heritage, where "Gut und Tite" was the rule (just short of stripping the threads), there has to be a method/standard for consistently tightening a bolt to properly perform its design function in the place it is being used. Usually there is a reference based on the bolt size, quality and thread spacing. This reference sometimes contains notes about lubricated threads and the effect on the torque. Aircraft reference tables don't mention using fiber locking nuts but it is hard to find a fastener in an aircraft that does not use them - including locking nut plates. Also, there is no special reference to high temp steel locking nuts. I use the AN bolt torque tables unless the use is only for shear or some other special application. For engine bolts/nuts, I reference the appropriate overhaul manual. I rationalize my use by noting that fiber/steel locking nuts do not add that much resistance - maybe a few percentage points above that of a non-locking nut. Good enough for me since I do not regularly re-calibrate my torque wrenches. I prefer that the bolts be slightly off torque rather than grossly off torque since my arm hasn't been calibrated in years either. Scott Krueger AKA Grayhawk LNC2 N92EX IO 320 SB 89/96 On Vacation -------------------------------1160233192 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 10/5/2006 9:26:12 P.M. Central Daylight Time,=20 leighton@teleport.com writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
The recent discussions about proper torque on such thi= ngs as=20 engine mount bolts reminds me that over the years I have heard from severa= l=20 normally reliable sources that using a torque wrench on locking nuts (eith= er=20 plastic or all metal) is not only a waste of time but possibly even a bad=20 idea.  The logic is that because of the built in interference of the=20= nut=20 either a lower than desired reading will be read or upon approaching the=20 desired torque the nut will "slip" and result in higher than desired=20 torque.  It's been pointed out that truly torque-critical items, like= =20 connecting rod bolts and case half connecting bolts never use locking=20 nuts.  In other words, if the torque is really important don't use lo= ck=20 nuts.  I am curious what others on the list might have to say about=20 this.  I am not an engineer, nor do I play one on TV, but I've been u= sing=20 nuts and bolts since way back in the Erector Set days and have absorbed "d= o"=20 and "don't do" advice from people whose expertise I respect, including the= =20 above observations on torquing fasteners.  I probably won't change wh= at's=20 worked well for me over the decades but perhaps someone has some compellin= g=20 argument to the contrary, or perhaps confirm what I've heard.  The fl= oor=20 is open.
Leighton,
 
Proper torque........Hmmmm...
 
Since I am a simple minded person, all I know is that there are many=20 bolt-type fasteners that must be tight enough.  Ignoring my heritage, w= here=20 "Gut und Tite" was the rule (just short of stripping the threads), there has= to=20 be a method/standard for consistently tightening a bolt to properly perform=20= its=20 design function in the place it is being used.  Usually there is=20 a reference based on the bolt size, quality and thread spacing. =20 This reference sometimes contains notes about lubricated threads a= nd=20 the effect on the torque. 
 
Aircraft reference tables don't mention using fiber locking nuts but it= is=20 hard to find a fastener in an aircraft that does not use them - includi= ng=20 locking nut plates.  Also, there is no special reference to high temp s= teel=20 locking nuts.  I use the AN bolt torque tables unless the use=20 is only for shear or some other special application.  For engine=20 bolts/nuts, I reference the appropriate overhaul manual. 
 
I rationalize my use by noting that fiber/steel locking nuts=20= do=20 not add that much resistance - maybe a few percentage points above that of a= =20 non-locking nut.  Good enough for me since I do not regularly re-calibr= ate=20 my torque wrenches. I prefer that the bolts be slightly off torque rather th= an=20 grossly off torque since my arm hasn't been calibrated in years either.=20
 
Scott Krueger=20 AKA Grayhawk
LNC2 N92EX IO 320 SB 89/96
 
On=20 Vacation


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