Boolean union sees one item vanish why?

Hi,
V5
two closed surface objects, union them and the bolt head vanishes.

Not sure why.

BOLT 0.5inch head fail Boolean union.3dm (1.5 MB)

Steve

Hello - the parts are not all closed. use ShowEdges to check, or SelOpenPolysrf.

-Pascal

Hi Pascal,
you just beat me to it, i did that and see the sliver, now wondering how to fill it as its a 4 sided gap.
surface from 2 3 or 4 edge curves doesnt work , bulged result.

perplexed.

solved it dupedge, sweep2 and use point.

As this was a download I wish folk were more careful with their work.

Steve