Investment casting (lost-wax) — for average-quality work, the typical dimensional tolerance that can be achieved is:

Introduction / Context:
Investment casting, also known as lost-wax casting, is renowned for excellent surface finish and high dimensional accuracy, enabling near-net-shape parts and reduced machining. This question asks for a representative tolerance achievable in average practice.

Given Data / Assumptions:

• Small to medium parts typical of investment casting.
• Standard wax pattern control and ceramic shell quality.
• “Average work” implies typical, not extreme best-case laboratory results.

Concept / Approach:

Compared to sand and shell moulding, investment casting provides the tightest tolerances among common casting processes. Typical capability is on the order of ±0.05 mm to ±0.1 mm for small features, scaling with size. Therefore, ±0.05 mm is a reasonable representative value from the available options for average high-quality industrial practice.

Step-by-Step Solution:

Verification / Alternative check:

Process handbooks and supplier specifications often cite ±0.05 mm for fine features on small castings, with looser tolerances for larger dimensions, confirming this choice.

Why Other Options Are Wrong:

“+0.2 mm”, “+05 mm”, and “+1 mm” are unilateral and relatively loose; they do not reflect typical symmetric precision achievable by investment casting.

Common Pitfalls:

Assuming a single tolerance applies to all sizes; in practice tolerance scales with length, but ±0.05 mm is representative for small dimensions.

Final Answer:

±0.05 mm