Help to merge polysurfaces to a single surface

I am working on a project and would like to convert those four polysurfaces into a single one. I am fairly new to Rhino and don’t really know how to do this.

Polysurfaces to a surface.3dm (232.9 KB)

Dear @Victor_Gukovsky
welcome to the forum.

_join
them - look in the commandline what s the result.
there are some inner surfaces that are not needed.
delete them - best before joining.

_delete
those surfaces

_join
the reaming surfaces

optimize the surfaces:
_extractSrf
_extractIsoCrv
(delete the co-cylindrical surfaces)
_extrudeCrv
for the chamfer-like surface you will need
_extendSrf
then
_trim
_join

Polysurfaces to a surface_fixed_tp.3dm (148.1 KB)

hope above helps.
maybe also check the great learning resources in rhino.
type _tutorials or find stuff here:

kind regards - tom

Thank you! It’s very helpful for the rest of the project :smiley: