— // — Parting line
Parting line · Fundición (ISO 10135) · ISO 1101
Example in plan
How to interpret it
On the drawing, “Parting line shown in side view with centerline” states a parting line requirement.
What controls
Trace of the plane along which the two halves of the mold or die separate. On the part it appears as a perimeter line that may carry flash, a small step due to mismatch between halves, and a change in draft direction on each side. The drawing shows it so it is clear where that mark will be and, therefore, where functional surfaces should not be placed. It is not a defect: it is an unavoidable consequence of the process, and it is only a problem if it falls where it gets in the way.
How to verify
The mismatch step is measured with a dial indicator or depth gauge resting on sound areas on each side, or with a feeler gauge at the ledge. In serious inspection, mismatch between halves is quantified by comparing corresponding points on each side with a portable measuring arm or scanner. Residual flash is checked visually and by touch, and its limit is set by the flash removal requirement, not by this indication.
Common mistakes when interpreting it
- Confusing the parting line with a lot defect: it is always there, and what is controlled is the flash and the step, not its existence.
- Placing a datum or a sealing surface right on it.
- Filing it by hand to “make it look nice” in an area that is measured later: that loses the reference for how much the part was shifted.
How to get it in the workshop / if it comes out of tolerance
Avoid locating or referencing on the parting line: the mismatch step between halves varies from part to part and ruins fixturing repeatability. If a sealing face crosses it, the drawing should call for local machining or set a limit on the step. When roughing a casting, the parting line is the best place to see whether the part has shifted between halves before cutting anything.
A step that grows over the production run indicates wear or poor closure of the molding flask, not a problem with that particular part: notify the foundry before continuing to machine the lot. If the step falls on a functional face, the usual solution is to leave stock and machine that area, not to sand it by hand. Before rejecting parts for shift, measure several: if they are all shifted by the same amount, the machining setup can compensate with a new work offset.
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Other symbols in Foundry (ISO 10135)
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