◇ Core mark
Core mark · Fundición (ISO 10135) · ISO 1101
Example in plan
How to interpret it
On the drawing, “Core mark permitted on non-functional face” states a core mark requirement.
What controls
Mark or imprint left on the part by the sand core support (the core print) or the element that holds it inside the mold. It appears as a pad, a recess or a change in texture on the surface, and it is unavoidable wherever the core needs support. The drawing indicates where it is permitted and, if the area is functional, how it is to be treated: removed, machined, or limited in height or depth.
How to verify
Depth gauge or dial indicator for the projection or depression relative to the adjacent surface, and a straightedge when the criterion is flushness. Visually, check that there is no residual sand or flash around it. If the mark is on a surface that must seal, what is really verified is the leak tightness of the assembly, not the depth of the imprint.
Common mistakes when interpreting it
- Treating the core mark as a random defect: it is an expected consequence of the process and the drawing states where it is accepted.
- Filling or dressing it by hand in a functional area instead of machining it.
- Fixturing on the core print, which is the least repeatable area on the entire as-cast part.
How to get it in the workshop / if it comes out of tolerance
Locate these marks before fixturing: a core print on a locating face makes the part rock. If the mark falls on a face to be machined, check that the machining allowance covers it; if it falls on a sealing face with no allowance, you need to raise a query. Its position also tells you where the core was supported, which is useful for understanding which way it may have shifted.
Mark deeper than permitted: it is corrected at the foundry by changing the design or support of the core print, not by dressing part by part. If sand is trapped around it, blast before machining. If the imprint falls right on a gasket seat, the usual solution is to add machining allowance and machine that face, or to move the core print on the pattern if the production volume justifies it.
Related symbols
Other symbols in Foundry (ISO 10135)
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