Because this standard is protected by copyright, official versions are typically paid. You can find them at the following sources: JIS B 1603: Straight Cylindrical Involute Splines
However, finding a clean, non-corrupted, and complete PDF version of this document for free has become a digital nightmare. Most links lead to: Jis B 1603.pdf Free Download Fixed
In some corners of the internet, a "fixed" file might imply a PDF that has been edited, cracked, or combined from different sources. However, in the context of industrial standards, this raises a significant red flag: Because this standard is protected by copyright, official