[PSUBS-MAILIST] conical hatch seat troubles

[hank pronk via Personal_Submersibles]

Hi All,I have a problem with my conical  hatch seat.  I have discovered that I have a .005 in gap between the hatch and seat in two spots.  It seems the seat is oval with a gap at each end.  I have no way of measuring this other than placing video cassette tape ribbon strips between the hatch and seat.  What I do is, I cut the ribbon into 3 inch strips, then tape them in place so they are hanging over the seat.  I put one every two inches, then close the hatch.  The ribbons are then trapped tight in the gap.  if the ribbons can pull out then there is a gap.  Sure enough, I can remove one at the front, so I put two ribbons on top of each other in that spot and it still pulls out.  I add another making 3 ribbons thick and it is tight.  Then I tried doubling one ribbon in the front and one opposite in the back and they were tight.  The conclusion is that the seat is oval by .005 in at each end.  I put the hatch back in the lathe and re-faced it, to be sure it is not the hatch.  It is the seat, it seems my flange facing machine is not perfect-not a big surprise.  This is still very good for a portable home made tool.I don't know if this a problem or not, how accurate does this have to be?  Will the assembly simply bend?  My feeling is the hatch and seat will deform to match under pressure.  To put it into perspective, I just measured a hair and that is .01 in. the same as the total gap combined.Hank
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