• Welcome to engineeringclicks.com
  • peg in hole problem - no play fit that locks but is easy to insert and remove

    Discussion in 'The main mechanical design forum' started by lamby, Feb 11, 2012.

    1. lamby

      lamby New Member

      Joined:
      Feb 2012
      Posts:
      2
      Likes Received:
      0
      Hi, This is my first post on the forum. Hopefully someone will be able to help me out.


      The problem I have is getting a no-play fit between a tube and a hole. The part in question is around 33mm OD (and min 20mm ID), around 800mm long. The requirement is for this part to fit into a hole and lock into place providing virtually no play in all directions and lock in place BUT is required to be easily inserted and removed (with some kind of catch?). With a standard peg in hole fit with plastic parts and moulding tolerances even low CPK values will mean that a worst case fit will translate to a large amount of play at the end of the 800mm tube.


      Ideas I have been experimenting with so far are non-locking taper fits (7 degrees or more). This works well however im struggling to work out how to keep the tube held down. The variation in tube/taper size diametrically means that the parts can vary vertically by a few mm and a catch would be required to work over this distance. The taper works well as long as the parts are held tightly face/face against each other. Any lift of the tube will result in the parts breaking away from each other when load is applied.


      This seems like quite a universal engineering problem however im still finding it difficult to find an application where it may be used already. Any ideas would be much appreciated.


      Just to add, the inside of the tube on both male and female parts (min 20mm) has air-flow and needs to be free of any restrictions.


      Kind regards
       
    2.  
    3. Erich

      Erich Well-Known Member

      Joined:
      Feb 2012
      Posts:
      221
      Likes Received:
      2
      You have discovered there is no free lunch. Tapers can hold without play but you lose axial location with diameter variation.

      Can you make the female part a split cylinder and use an external clamp or a pinch bolt arrangement to hold the shaft tightly?
       
    4. tonycro

      tonycro Well-Known Member

      Joined:
      Nov 2011
      Posts:
      78
      Likes Received:
      1
      circlip around the end of the shaft ?
       
    5. lamby

      lamby New Member

      Joined:
      Feb 2012
      Posts:
      2
      Likes Received:
      0
      The design is for a consumer product, I need the tube to be easily inserted and removed from the taper with some kind of catch that can be operated by a push/pull rod/wire from the other end of the tube. I was thinking some kind of self opening catch that will work over the vertical tolerance difference with something that will then stop the catch from opening like a rod behind the catch.

      im quite stuck on this one, all ideas are much appriciated!
       
    6. Ramana Rao

      Ramana Rao Well-Known Member

      Joined:
      Jan 2012
      Posts:
      47
      Likes Received:
      0
    7. vic.blackall

      vic.blackall Well-Known Member

      Joined:
      Feb 2012
      Posts:
      45
      Likes Received:
      0
      Perhaps a course screw thread with the same taper as the tube at the base of the tube.
       
    8. Dana

      Dana Well-Known Member

      Joined:
      Sep 2010
      Posts:
      341
      Likes Received:
      3
      Look here and scroll down to the section on "expanding pins".
       

    Share This Page