Cracks, wrinkles, springback, uneven thickness, dents, and tool marks

What to take away

Stop at the first crack, fold, sharp dent, sudden stiffness, or unexpected change in sound.
Preserve measurements and photographs before flattening, annealing, filing, or polishing.
Springback is a material-and-geometry response, not proof that the piece needs harder blows.
A smooth surface can still conceal unacceptable thinning.
Confirm corrective changes on documented coupons before returning to high-consequence work.

Forming defects often overlap. A wrinkle can become a fold, a fold can crack, and polishing a dent can create a thin zone. Diagnose the earliest observable event rather than only the final appearance.

Cracks and edge splits

Map the crack's location, direction, length, and relation to edges, solder seams, tool marks, grain direction, and prior bends. Do not close it with hammering or heat it before deciding whether repair is allowed.

Work hardening increases hardness and strength while reducing ductility under plastic deformation, as summarized in the work-hardening reference. That principle can help frame a hypothesis, but contamination, alloy mismatch, overheating, deep scratches, and poor geometry can also initiate cracks.

Reject or refer the piece when the crack crosses a structural section, repair would violate disclosure, or remaining material cannot meet the drawing.

Wrinkles and folds

Wrinkles show that material is not being controlled evenly. Check support contour, course angle, spacing, rim behavior, blank shape, and whether excess material is accumulating in one sector.

Stop before a wrinkle closes into a fold. A folded layer may trap scale and produce a crack or hidden void. Do not hammer it flat and call the surface repaired.

Springback

Measure the part on the tool and after release. The difference is process data. Check alloy, temper, section, bend radius, orientation, prior working, and annealing state.

Correct in small symmetric steps. Excess overbending can move the error elsewhere or create a kink. A repeat job needs a recorded compensation based on the actual batch and setup.

Uneven thickness

Create a station map. Measure likely stretched zones, tight radii, edges, transition points, and the nominally unchanged center. Mass alone cannot reveal a local thin spot.

If thickness falls below the requirement, polishing or reshaping does not restore it. Redesign, reconstruct, or reject the part.

Dents and tool marks

Separate intended hammer texture from accidental sharp contact. A single deep mark may come from a chipped face, debris on the stake, a glancing blow, or unsupported work.

GIA's goldsmith-hammer modification lesson describes face and handle preparation for shaping and forming tasks. It supports matching and maintaining a hammer for its job, not grinding or altering a damaged tool without qualified control.

Do not remove a dent by sanding the entire area until it looks level. Measure depth and remaining section, then decide whether burnishing, controlled planishing, local refitting, redesign, or rejection is permitted.

Root-cause worksheet

Record:

Evidence	Question
Tool-face impression	Is the same defect present on the hammer or stake?
Location repeats	Does support or grip change there?
Defect follows an edge	Was the edge scratched or overworked?
Thickness drops locally	Did blows stretch instead of compress the zone?
Springback rises by course	Did work condition change between measurements?
Crack appears after heat	Was material, temperature, atmosphere, or cooling incorrect?