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Problem with 'O' Ring Tolerance?

  1. Jun 20, 2011 #1
    It may seems like simple homework question but it is industrial question with actual condition & I am struggling for the answer & also asked this question on other website but not get any reply. So ,please help me

    'O' ring Internal Diameter(ID) ID=4 mm with tolerance is + & - 0.15mm. Tolerance as per in most of the standards.
    I design shaft of 4.0+0.15=4.15mm for maintaining minimum stretch of 0.00mm in any condition.
    If Shaft dia is 4.15mm & minimum 'O' ring ID is 4-0.15=3.85mm then 'O' ring stretch is 4.15-3.85=0.3mm.
    'O' ring stretch percentage is 0.3/3.85 * 100=7.79 % > 5% alowable limit.

    Please tell me is there any other solution for this OR all the industries make compromise in stretch with small ID 'O' ring.
    I not gives any tolerance on shaft. If I will give then Stretch increase more & so intensify the problem.
  2. jcsd
  3. Jun 20, 2011 #2
    I am not sure where the 5% allowable stretch limit came from, but if you must meet this, I would recommend to talk to the o-ring manufacturer and see if they will deliver a batch with the tolerance you need. There will probably be a price adder as they will have to sort and measure their inventory.
  4. Jun 22, 2011 #3
    In Parker 'O' ring handbook, Dichomatik 'O' ring handbook & Eriks 'O' ring handbook Stretch limit given as 5% maximum. However, I tried to contact so many industries from last 3 weeks & finally I find one which gives me desirable tolerance which I required. So, my problem is solved.

    Thanks for reply
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