These ordnance drawings reproduced in high quality by Nicolaus Associates are a must have for anyone who works on 1911s or is simply a fan of the platform.
I periodically get inquiries from former students and visitors of this site asking if their 1911 is in or out of spec. With countless manufacturers of the 1911, and even more aftermarket suppliers making slides and various small parts, without the original source material (the original blueprints,) it is hard to tell whose parts are in spec and whose is not. The resource I used in the past were the Kuhnhausen Manuals. Unfortunately, the drawings are not complete and contain some typographical errors. A few years back, a buddy of mine turned me on to the original 1911 ordnance drawings available from Nicolaus Associates. 
These drawings are essentially the complete set of ordnance blueprints for every part of the originally M1911A1. While the drawings certainly won’t turn the layman into a gunsmith, it provides a baseline for which the reader can determine whether or not a part is within specified dimensions, as long as they have basic measuring skills with a caliper. Per the publisher, these drawings were obtained through numerous inquiries via the US Army Freedom of Information Act officers and technicians. The book itself is spiral wire bound and printed on 8.5×14 inch 24-kb quality paper. It is at home in your shop or coffee table, and is a must-own for any 1911 enthusiast, armorer, or gunsmith. HERE is the direct link to the page where you can order M1911A1 Diagrams and Pictures Book. Scroll down a little and you’ll see it.