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If you meant a (e.g., military standard, technical report, or part of a building code like “Part 5” of some national regulation), please clarify — the answer may differ.

Many engineering colleges, architectural firms, and large construction companies subscribe to the BIS library or third-party compliance databases (like IHS Markit or Techstreet). If you are a student or an employee, checking your organization’s digital library is the safest and most cost-effective way to access the code.

It sounds like you're looking for a free PDF of (likely referring to a standard related to textile machinery or similar, though the exact ISO 3646 series is less common; you might mean ISO 3646-5:1991 on spinning machinery — or possibly a misprint of another standard like ISO 14646 or IEC 3646?).

: The most current and authorized version should always be verified on the official BIS Portal , where digital copies usually carry a fee. Public Resource 3. Related Parts in the Series