[Woodworking Brendan]

Hi Everyone,
I was walking through the park today and came across this bridge. I can not understand how they made the top and bottom of the vertical pieces rounded. I suppose it would be easy enough to do on a wood lathe except for the fact that this piece would not spin very evenly, or would that not be a problem? I am very curious to know if there is any type of hole saw/drill bit that could go over the end of any such piece of timber and leave it perfectly round each time to be inserted into a hole made by a hole saw, such as in my attached photos?
Thanks for any ideas and advice, Brendan.

 

[woodnthings]

no lathe required

these will do it:
Lumberjack Tools TTA2000 Industrial Series 2-Inch 60 Degree Tapered Shoulder Tenon Cutter - Amazon.com
and a big arse drill to power them.:yes:

 

[cabinetman]

Here is another image...
.

.

 

[ACP]

Leevalley carries a line of tenon cutters and mortising tools for rustic work like that.