Our mandrels are 5/8″ diameter, with a length of 5.5″. They are straight shank and made to be used in a collet chuck or can be used with a 4 jaw chuck. This mandrel has no knurling. All our mandrels have a black oxide coating applied to help with rust prevention.
Smooth/No knurling is used for clear or transparent acrylic to help reduce scratching.
Fine knurl is designed for use on acrylic (especially clear/transparent) where as little scratching as possible is needed inside the barrel.
Rough knurling can be used with either wood or acrylic but was designed for use on wood where you want more bite and inside scratching isn’t as important.