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mate .112 dia screw into a .136 dia hole

Question asked by Ken Hurst on Mar 20, 2019
Latest reply on Mar 21, 2019 by Paul Risley

Hi,

 

  I have an issue.  I'm trying to mate a 4-40 screw into a hole using concentric mate in an aircraft relay box.  The issue is that the screw diameter is 0.112 and the hole diameter is 0.136 and solidworks flags it red.  This is by engineering design (item was designed over 40 years ago and was a modification).  Is there a way to properly mate this so that it is properly defined?

 

There is a 4-40 screw (MS35206-214) with a AN960D4L washer (hole dia is 0.112) going through a hole in the relay box chassis (0.136 dia).  It also goes through a sheet metal assembly (just a flat piece of aluminum) that also has a 0.136 dia hole.  A 4-40 self locking nut (MS21042L04) is used to secure the fastener.

 

I have successfully mated other screws, washers and nuts to the relay box chassis but these have all had the same diameter shafts and holes.  Issue here was a relay originally mounted here used screws with shaft dia of 0.136 along with washer and nut of same 0.136 hole diameter.  Later, relay was changed out that needed a sheet metal piece to bridge cutout gap (new relay s smaller) but also used 0.136 dia holes.  To prevent the need from having atypical mounting holes in the relay box chassis, 0.112 shaft dia screws were chosen since mounting holes are 0.136 with a tolerance of -0.001 and +0.005.  Why this was chosen is beyond me.

 

Any suggestions would be greatly appreciated

 

Thanks

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