How To Get More Information From Slug

Inspect cross-section. A perfect slug from a thick turret press should be roughly 1/3 smooth (burnish) and 2/3 rough (break).

The Four Key Anatomy Zones of a Slug

When you pick up a slug from the scrap bucket, look for these four distinct characteristics:

A. The Roll-over (Top Edge)

This is the rounded part of the slug's top circumference.

What it tells you: If the roll-over is excessive (too deep), your die clearance is too large. The punch is "stretching" the metal into the die too much before the shearing starts.

B. The Burnish Zone (Shiny Band)

This is the smooth, vertical band just below the roll-over. This is where the punch physically cut and rubbed against the metal.

What it tells you: Ideally, this should be about 25% to 33% of the material thickness. If the burnish zone covers the entire side of the slug, your die clearance is too tight, causing "double shearing" and massive heat buildup.

C. The Fracture Zone (Tapered/Rough Area)

Below the shiny band, the metal looks grainy and slightly tapered. This is where the material reached its limit and snapped.

What it tells you: In a healthy setup, the fracture should be consistent all the way around the slug. If the fracture is deeper on one side than the other, your punch and die are misaligned.

D. The Burr (Bottom Edge)

This is the sharp "lip" at the very bottom.

What it tells you: A tall, sharp burr is the universal sign of dull tooling. When the punch is dull, it "tears" the last bit of metal instead of snapping it cleanly.