From: noel shelley (noel@shelley1722.freeserve.co.uk)
Date: Sat Jun 19 2004 - 08:12:51 PDT
Gentlemen ,
The reason for only trying to heat the bolt/screw is
that it is the movement of expansion and contraction that`s needed . The
rust acts as a barrier allowing the bolt/screw to be taken to red heat
quickly using oxy acetylene without damage to the surrounds , and also the
heat will break down the rust . Some annealing may take place , relieving
the work hardening resulting from thread rolling , the need for wd40 or
similar is that any lubrication will have been destroyed by the heat .
In using heat on assemblies one must consider the effect heat may have on
other components , seals , gaskets, bearings some of which may have plastic
cages ,Etc , or distortion that uneven heating could cause.
Yes Arthur , your right about the freezer , common trick , particularly
fitting bearings , heat the outer part ,put the other in the freezer , or
vice versa . Aluminium has a high rate of expansion ,as does brass , cast
iron and steel very little .
I operate a small non ferrous foundry , shrinkage , the change in size
resulting from the change in state from liquid to solid , plus the
subsequent contraction due to cooling to room temp, in brass is in the order
of 3/16" per foot , a 17" casting will be 1/4" shorter than its pattern ,
and has to be allowed for .
All of academic importance as I believe Cor has got his screws out but may
be of interest !
Noel
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