Date:         Tue, 27 Sep 2011 21:33:53 -0700
Reply-To:     Don Hanson <dhanson928@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Don Hanson <dhanson928@GMAIL.COM>
Subject:      Re: Torque Specs - Lug bolts and nuts
Comments: To: Gary Bawden <goldfieldgary@gmail.com>
In-Reply-To:  <CACHTzadzs5mfhuUJbaebXcCo8+u6veMSoMHY=imceqB-ZpUK1g@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

On Tue, Sep 27, 2011 at 8:51 PM, Gary Bawden <goldfieldgary@gmail.com>wrote:

> Snipped.
>
> I believe the engineers know this, and set torque values to a number that
> they believe will do the job, without over-stressing the part. And as has
> been pointed out by others, it's the uniformity of torquing fasteners (at
> least on parts having more than one) that is probably more important than
> the actual torque value.
>

  One thing to keep in mind about torquing something to specs....Depending
on the parts connected by the torqued nuts, bolts, studs, whatever....they
should often times not be taken right to the specified torque, all in one
tightening.   When I do alloy wheels up to 100lb/ft....I go round to about
80 in a star pattern, then I re-set the wrench and do it up the final 20lbs.

  My engine  mechanic used to take two full days to torque the heads on the
928 motor....he would (I don't have exact numbers) torque em up to about 50%
and leave em all day, then come back and go to like 80% and leave em again.
then again with a 'resting, settling period' and finally go to full
torque...

  Castings seem like they are pretty brittle, somewhat fragile...If you are
to torque say a water pump to (out of thin air, this figure) 30ft/lbs....I
wouldn't feel right just doing it up, one fastener at a time, right to
30lbs...I'd probably snug it up, then torque to 20, then go back and go at
it with 30ft/lbs....minimize and spread the stress.