Deep bore gauge.
Fullsize image: https://diqn32j8nouaz.cloudfront.net...e_fullsize.jpg
https://diqn32j8nouaz.cloudfront.net...bore_gauge.jpg
Previously:
https://www.homemadetools.net/forum/...343#post122020
https://www.homemadetools.net/forum/...823#post137092
https://www.homemadetools.net/forum/...820#post148359
https://www.homemadetools.net/forum/...684#post147799
https://www.homemadetools.net/forum/...453#post154787
