Foundry pattern colour code — marking surfaces to be machined In standard foundry practice, which colour is used on the pattern to indicate surfaces that will be machined after casting (so extra machining allowance is provided)?

Introduction / Context:
Pattern colour coding communicates allowances and special requirements to moulders and machinists. Correct colours avoid costly errors like insufficient stock for machining or missed core prints.

Given Data / Assumptions:

• Conventional Indian/British foundry colour codes.
• Solid wood or metal patterns with painted areas.
• Objective: identify machining allowance areas.

Concept / Approach:
Surfaces intended for machining are painted red on the pattern. Core prints are often painted yellow; surfaces that must not be machined may be left natural or painted other designated colours depending on local standards. The red marking ensures that the moulding process includes extra stock on those faces to permit finishing operations such as turning, milling, or drilling.

Step-by-Step Solution:
Recall standard code: red = machining allowance.Identify the option matching this code.Select “red colour”.

Verification / Alternative check:
Many foundry manuals and training charts depict patterns with red faces where machining will occur and yellow on core prints.

Why Other Options Are Wrong:

• Yellow: typically for core prints.
• Black/Blue/Green: not the standard for machining allowance in most systems.

Common Pitfalls:
Confusing core print colour with machining colour; this leads to missing or misplacing cores or allowances.

Final Answer:
red colour