Books

Many eBooks in public domain, old but still of great value, a short selection of some that I have read

Clocks and watches

Clock and Watch Escapement Mechanics, by Mark V. Headrick

How to design a clock and/or a watch escapement, easy to follow step by step

Link to eBook: http://www.abbeyclock.com/escpdf.html

Traité d'horlogerie moderne: théorique et pratique, De Claude Saunier, 1869

Détaillé et technique, montres et horloges, echapement, engrenages et moteurs, pendules et balancier

https://books.google.fr/books?id=vX1JAAAAYAAJ&printsec=frontcover&hl=fr&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

A Treatise on Modern Horology in Theory and Practice · Claudius Saunier · 1887

A complete study of watches and clocks, the escapements, gears and motors, pendulum and balance wheel

https://www.google.com/books/edition/A_Treatise_on_Modern_Horology_in_Theory/1yVYAAAAYAAJ?hl=en

Les Gravures de bonnes qualités, Ilustrations in a great quality

https://www.cliniquehorlogere.ch/fr/news/traite-horlogerie-par-saunier.html

On the construction of a simple and mechanically perfect watch, Moritz Grossman, 1880

http://www.watkinsr.id.au/grossman.html

A practical and theoretical treatise on the detached lever escapement for watches and time pieces, Moritz Grossman, 1884

https://archive.org/details/practicaltheoret00gros/page/34/mode/2up

Spiral, hairsprings, etc

The Art of Making Watch Mainsprings, Repeater Springs and Balance Springs, William Blakey, 1780

A detailed description of how watch springs were made in the 18th century

http://www.watkinsr.id.au/blakey.html

The Watch & Clock Makers' Handbook, Dictionary and Guide, Frederick James Britten, 1896

Balance spring making and more

https://archive.org/details/watchclockmaker01britgoog/page/n34/mode/2up

Mémoire sur le spiral réglant des chronomètres et des montres, Phillips, E, 1860

The math of the hairspring, and of the shape of the end curves

http://sites.mathdoc.fr/JMPA/PDF/JMPA_1860_2_5_A27_0.pdf

Others Book List:

https://theindex.nawcc.org/OnlineBooks.php

https://mb.nawcc.org/threads/digitized-books-related-to-watches-and-watchmaking.53214/

http://www.watkinsr.id.au/index.html