Dowel sizer and groover
I am rarely satisfied with the fit of dowel diameters available, especially when supposed metric sizes are still imperial.
I size my dowels by chucking a length in my drill after chamfering the ends and running them through an offcut of flat mild steel which has been drilled with the nominal sized hole. If the result is still too snug, I'll repeat on a slight angle until I'm happy with the fit. I believe that the compression will be expanded by the water based PVA as per plate joiner biscuits.
To machine the glue escape groove, I fit the dowel into a block of scrap and run into the bandsaw blade.