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Contraction of steel piece

  1. Feb 13, 2012 #1
    Hi,

    To simplify the explanation of my problem, imagine that I have in my hand a rectangular steel piece of 1.5mm thickness with a hole of 2mm diameter.

    In the other hand I have a small tubular steel piece 10mm length x 2mm diameter.

    I have to put this tubular piece into the rectangular piece, but I need it to hold very strongly.

    I know that steel is contracted with cold, is it possible to create the tubular piece with 2.1mm diameter, subject it to cold to reduce the diameter, insert it into the hole and heat it to return the piece to its original dimension?

    is this crazy?
     
  2. jcsd
  3. Feb 19, 2012 #2
    Your right on the money!
    Some machine shops supercool parts to make them fit without hammering on them.

     
    Last edited by a moderator: Sep 25, 2014
  4. Feb 20, 2012 #3

    OldEngr63

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    Gold Member

    Heating holes to expand them and/or cooling inserted parts is all a part of what is referred to as making a "shrink fit." This is a well developed art, tending to be a science. See for example Den Hartog's Strength of Materials and Advanced Strength of Materials books. He discusses this at length.

    This is very commonly done to mount rotating parts on a shaft. The shrink fit is often the sole basis for the torque transfer (friction in the shrink fit transfers the torque), so it must be sufficient to carry the required torque. As the parts rotate more rapidly, the shrink fit will tend to loosen because of centrifugal loading, so it is necessary to calculate the shrink fit at operating speeds to assure that there is sufficient friction to carry the load. It is also important not to shrink the part on with an excessively heavy load as it can crack the outer part, leading to a premature failure. This is a well developed and interesting part of mechanical engineering science.
     
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