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Question

Difficulty: HardStriking Tools

When reconditioning a cold chisel or center punch that has developed a mushroomed striking head, the flared metal must be ground off and finished with a slight chamfer or crown rather than ground completely flat with sharp square edges.

Answer: Answer

Answer

True
Dressing a mushroomed punch or chisel requires grinding away all work-hardened, flared steel until sound metal is reached, then finishing the crown with a beveled or chamfered shoulder. This geometry aligns impact shock along the tool's centerline and eliminates weak perimeter lips that can shatter into high-velocity projectiles.

Step-by-Step Solution

1
Analyze the failure mechanism of a mushroomed tool head.
Repeated hammer blows flatten and work-harden the perimeter metal of the tool head, creating brittle flared lips.
Understanding work-hardening and deformation explains why damaged struck heads represent a severe fragmentation hazard.
2
Evaluate the stress distribution of a chamfered crown versus a square 90-degree shoulder.
A slight chamfer or crowned perimeter prevents localized shear stress concentration and keeps impact shock centered.
Sharp square corners create intense stress risers that quickly chip, crack, and throw dangerous shrapnel when struck.
3
Determine whether the reconditioning procedure described is correct.
The statement accurately reflects standard shop safety maintenance for all struck hand tools.
Proper dressing requires grinding back the flared metal to sound steel and adding a 45-degree chamfer or crown.

Key Concept

Struck tool maintenance, mushroomed head hazards, and edge dressing geometry
Estimated Time:1m 15s
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Topics

Striking Tools

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