Pattern design — the machining allowance provided on patterns depends on which of the following factors for practical casting operations?

Introduction / Context:
Machining allowance is an intentional extra material added to the casting dimensions to permit removal of surface irregularities and achieve final tolerances by machining. Correctly sizing this allowance is crucial for cost, quality, and avoiding undersized parts after finishing.

Given Data / Assumptions:

• Different alloys exhibit different casting surface qualities and dimensional stability.
• Larger and more complex shapes risk higher distortion and surface defects.
• Casting methods vary in accuracy and surface finish, influencing required stock for machining.

Concept / Approach:

Allowance selection is multi-factor. Metals that oxidize heavily or have poor surface finish need more stock. Large castings accumulate more defects and may require greater allowances. Precision processes like investment casting need less; sand casting often needs more. Therefore, the allowance depends on all listed factors and not a single one in isolation.

Step-by-Step Solution:

Verification / Alternative check:

Foundry handbooks provide allowance tables indexed by alloy, size range, and process, confirming the multi-factor dependence.

Why Other Options Are Wrong:

Each single factor alone is necessary but not sufficient; only “all of these” captures the complete practical basis for allowance selection.

Common Pitfalls:

Using a fixed allowance regardless of size or process; ignoring extra stock for heavy scale or distortion-prone geometries.

Final Answer:

all of these