Anyhow, it described how the machine was used and how the rifling was cut. Each grove was cut, one pass for each of the seven groves and then a "paper shim" was inserted to raise the cutter and then each grove was again cut in order until the depth reached "10 to 14 papers deep".
Now if there was some reference to the thickness of the "paper shims", I could have provided an answer to your question
I am NO expert, but have been doing some research into the linen paper of the day. This is one of the best descriptions I found of 18th and early 19th century paper – before wood pulp paper became common after the UnCivil War
“The first step in preparing the rags was to sort according to color and quality. The higher grades of paper used only white rags of a higher quality of linen content. This was called "grade one." The smallest and largest sheets of paper were made from this quality of rags and linen. The smallest sheets were used for writing paper and documents. The largest were reserved for atlas printing. Newspapers were printed on "grade two" paper. "Grade three" was reserved for wrapping paper, wallpaper, boards for bonnets, and so forth.”
And
“In order to print on the paper it had to be specially treated. Treatment consisted of dipping each dried sheet of paper into a vat of sizing. Sizing was made from animal parings -- tissue and bits of flesh scraped off the hides -- which were then boiled into a gelatinous liquid. After dipping and shaking the excess sizing off, the sheets were then placed on felts and returned to the screw press. This pressure helped bond the sizing to the paper and removed any excess sizing.”
http://www.historybuff.com/library/ref1690.htmlWhat kinds of paper would the Hawkens used to make shims? I imagine their account books and papers used for correspondence would have been the most expensive Grade 1. For shims I imagine they would have used newspaper Grade 2 or wrapping paper Grade 3? I get the impression that Grade 2 was not as thick as Grade 3, but I have yet to find anyone who mentions how thick the period paper generally was.
Modern Linen paper runs about .007”, but that is probably more uniform and consistent than Grade 1 was in the 18th and 19th centuries? A GUESS is paper they used to make shims from ranged from .008” or .009” to maybe .012”. The different thicknesses would explain why they used between 10 to 14 shims of such paper?
What I DON’T know is how much that paper compressed when forced against the bore to press the rifling cutter deeper.
Sorry, but that’s the best I’ve been able to find so far.
Gus