Parting Line
Most engineers treat the parting line as a manufacturing detail. It is actually a structural decision, because a badly placed parting line puts exposed fibre ends at the highest-stress location on the part.
The parting line is where the two die halves meet on a forging. Its placement determines where flash forms, how metal flows into the cavity, and critically, where grain fibre ends surface on the finished part.
- Definition
- Where the two die halves meet
- Determines
- Flash location and fibre end position
- Preferred
- Largest cross-section, flat plane
- Avoid
- Stressed fillets, sealing faces
Parting Line at a glance
Quotable facts from Avadh Techno Forge, Gundasara, Gondal, Rajkot.
- Definition: Where the two die halves meet
- Determines: Flash location and fibre end position
- Preferred: Largest cross-section, flat plane
- Avoid: Stressed fillets, sealing faces
It Determines Where Fibre Ends Surface
Grain fibre runs through the forging and terminates where flash is expelled. If the parting line sits at a highly stressed fillet, fibre ends surface exactly where a fatigue crack would start — turning forging's central advantage into a liability.
Practical Placement Rules
Place it on the largest cross-section, ideally on a single flat plane, away from stressed fillets and functional surfaces. A stepped or curved parting line is possible but raises die cost and mismatch risk.
Topics covered on this page
- parting line forging
- parting line placement
- what is parting line
- forging die split line
Based on work carried out at our own forging plant at Gundasara, Gondal, Rajkot — operating since 2008.
Questions Answered
What is a parting line in forging?
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The line where the two die halves meet, which determines where flash forms and where grain fibre ends surface on the part.
Why does parting line placement matter structurally?
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Fibre ends surface at the parting line. Placed at a stressed fillet, they become a crack initiation site.
Where should the parting line go?
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On the largest cross-section, ideally flat, and away from stressed fillets and functional surfaces.