Thought I might share some recent wisdom.
I'm in the process of building a rod for a customer and the Fuji SK2 split reel seats will be going on. I wanted to build a new hood front end grip but was trying to come up with a way of boring out the damn 20mm hole that the cork will slide onto. So I came up with the following;
-I bought a 20mm and 28mm spade drill bits
-Loaded a 45mm thick piece of timber onto my drill press and bored a hole with the 28mm spade drill at a depth of 40mm.
-Ground down the wings of the 20mm spade bit.
-Meantime, i had already turned my cork at 40mm length and 28mm diameter.
-I then taped the cork for extra strength incase the sides blow out when I'm drilling the hole.
-Inserted the cork into the hole in the timber and made sure it was a tight fit.
-Then slowly drilled the hole into the cork at a depth of 28mm.
Came out prefect. Fits nicely on the front end split reel seat.
The reel seat is a size 16 in case you're wondering.