Forging tools — fullers are primarily used for which operation during hot-work to control metal flow and cross-section?

Introduction / Context:
In smithy and forging practice, specialized tools are used to direct metal flow efficiently. Fullers (top and bottom) are rounded-groove tools that indent hot stock to redistribute material. Knowing their primary function is essential for planning preform shapes prior to drawing, bending, or upsetting operations.

Given Data / Assumptions:

• Hot-working conditions with fullers used in pairs (bottom fuller in anvil/hardy hole and top fuller under hammer/press).
• Objective: locally reduce section or create shoulders/grooves to facilitate subsequent shaping.
• Distinguish from punches and drifts used for hole making/finishing.

Concept / Approach:

Fullering produces localized thinning and spreading of metal away from the groove, effectively necking down the work. The fuller impression encourages longitudinal flow on either side, creating a reduced section (a neck) and raised fillets/shoulders that can later be dressed by flattening or swaging. It is a preparatory step for controlled elongation and for defining transition radii.

Step-by-Step Solution:

Verification / Alternative check:

Shop manuals depict fullering as the standard method for necking and shoulder formation, whereas punches/drifts are specified for hole creation/enlargement and bottom/top swages for finishing radiused sections.

Why Other Options Are Wrong:

Finishing flat surfaces is done with flatters; punching is done with punches; finishing holes is done with drifts/reamers—not fullers.

Common Pitfalls:

Using a fuller to finish surfaces (leaves grooves); forgetting to follow fullering with dressing to remove marks.

Final Answer:

for necking down a piece of work