Boolean Operation Failed

Hello I’m trying to make a “flow cell” object for a 3D printer but using a series of successive boolean difference operations.

Ie substracting cylinders, etc from a block to build up a flow.

I am having a problem then once I have substracted and applied a single successful operation, further operations fail.

In the attached file I have subtracted a screw thread from a box and I now want to subtract a cylinder that is the same diameter as the tube that goes through the screw.

The operations fails and doesn’t allow me to do it.

I have tried, removing double, selecting non manifold vertices (0) converting to tris and quads but still I don’t think it will allow the operation because some of the faces of the subtraction are parrallel and co incident.

Is there a simple solution to this?


FlowCell_1a.blend (1.83 MB)

Did not like the mesh. I duplicated it and it deleted the first and it appears to have worked on the new.