Designing Prongs That Survive Casting: A CAD Checklist

Prong failure is the most common defect we see in jewellery casting — and almost all of it traces back to CAD decisions made long before metal is poured.

Minimum Dimensions That Actually Work

For 18K gold, we never model prong tips below 0.8mm diameter, and we pre-thicken tips by 15% knowing setters will cut seats into them. For 14K, which is stiffer, 0.75mm is workable.

Shrinkage Is Not Optional

Gold alloys shrink 1.25–1.75% from model to finished piece. Every Auric file has compensation applied — but if you re-scale a design, remember the compensation scales with it.

Support Where It Matters

A prong that meets the gallery rail at a hard 90° angle concentrates stress. We fillet every prong-to-gallery junction at a minimum radius of 0.2mm, which is invisible after polishing but dramatically improves survival rates.

Test Before You Publish

Every design we sell has been resin-printed and inspected under 10× magnification. It is the only way to catch what a render cannot show.