To bring your octagon into a round, simply plane your 8-sides
into 16 sides. This is easily done by eye without any additional
marking. Then once you have 16 sides, you can use any spoke
shave, block plane or smoothing plane to whittle those 16 sides
into round followed by sanding.
Öor you can use use a spar plane (see
my article) - to go from 8 sides to round in one passÖ
The beauty of spar planes is that with a sharp blade and
straight grain, sanding isnít required at all. And these
8-siding gages donít have to be crude like mine:
Boatbuilder Jon Etheredge sent me a pic of his shop-made marking
gage, a copy of a rare beauty in the Mystic Seaport Museum,
which I have filed away to make one on rainy winter day.