Drilling a vertical hole in fence post
(Sorry I'm not Metric, we use 2x material)
Dado out a wooden Post for the pole, then add a 2x to the side you dadoed out to cover it and screw it to the dadoed post and bolt the whole thing together 

Depending on the Diameter of the post, you can also wrap it in 2x. We have also done 2x6 Left to right (So you see the 2x6 face on the fence, I like 4x6 Fence Posts.  Then between them, also flush against the post, cut a 2x to fit between the 2x6 and bolt though the side 2x4s. 

Sizing might be off, but I think you can get what I'm describing?
We use Carriage bolts on the side you see and counter sink the nuts.