About 6 years ago, I went to the Colonial Williamsburg Gun Shop and asked the same question, "What did an 18th century Turnscrew look like?"
They handed me a couple repro's to look at. I'm sorry I don't have a camera to take photographs, but imagine a full tang knife with wood slabs pinned to each side of the grip. The steel was about the same thickness as a knifeblade as it was a good sized blade on it. The front portion ahead of the grip was just angled down on both sides to the edge of the tip on each side. Very simply made and practical.
OK, so I asked about period hack saws and some other tools. THEN they pulled out a reproduction of John Wyke's "A Catalog of Tools for Watch and clock makers." The copy they had in the shop matched the original catalogs and did not have explanations of the tools. Wow. WoW !!
Then I asked them if I could get a copy of it and they said they had published it years ago and thought it was available in the book store. Well, it wasn't, and it was out of print. I found one on Amazon and paid about $ 125.00 for it. About a year later, I found another on EBay and got a "great deal" on it for a little under $ 50.00.
SUPERB NEWS, it is back in print and only $ 35.00
http://www.thebestthings.com/books/toolbooks.htmSome of these engraved plates date back to 1758, some were added in 1770 and the last few plates added around 1810 (if I remember correctly on the last date.) Colonial Williamsburg has one of the only four or five known original copies and they use this book as a primary source for authentication and replication of 18th century tools.
This book has illustrations of the engraved plates and explanations of each plate for 18th century files, engravers, chisels, turnscrews, hammers of all sorts, pliers of all sorts, dividers, calipers, many styes of pin, hand and bench vises, drills, drill bits, hack saws, coping saws, jewelers saws, wire drawing plates, screw plates and taps, braces, anvils, metal shears, and of course a host of tools used by clock makers.
John Wyke (I'm told it is pronounced "Wick") was a wholesaler of tools and not many of these catalogs were ever printed as they cost so much to print in those days. Wyke had small jobbers make all the items in the catalogs in local shops and he gathered them up and wholesaled them. It was well known that perriod gunsmiths bought and used many of these tools.
I only recently found out it was back in print and I'm very excited it is once again available. I have a host of books on early american tools and NONE of them are anywhere CLOSE to as good as this book for the 18th century.