A client came to us with a CAD model for an engagement band that looked elegant on screen: a slim 1.2 mm shank tapering to a Cathedral head. The rendered weight read 2.8 g. When we cast it, three out of ten rings showed a porosity pinhole along the inner wall after pickling. The design was not wrong; it was 0.3 mm too thin for a reliably castable sterling and 14K shank. CAD wall thickness is a design choice, but it lives inside a manufacturing envelope.

The numbers we model to

Wall thickness is measured at the thinnest point of the shank, usually at the bottom of the ring opposite the head. Our default minimums, measured in millimeters, are:

  • Sterling silver comfort-fit band: 1.4 mm minimum wall, 1.6-1.8 mm typical.
  • 14K yellow/white gold band: 1.2 mm minimum, 1.4-1.6 mm typical.
  • Platinum (950): 1.3 mm minimum because platinum is denser and casts thinner detail but wears slower.
  • Stackable / midi rings: 1.0 mm minimum accepted, with a weight warning on the approval sheet.

These come from the shrinkage and castability rules we follow, documented alongside our silver casting shrinkage tolerances and jewelry CAD tolerance defaults. Gold content itself is governed by marking rules; the 16 CFR Part 23 gold marking guide sets the karat expectations the final piece must meet.

Wall thickness vs comfort and weight

Thicker walls feel substantial but drive up gram weight and therefore cost. A 2.0 mm shank on a plain wedding band weighs roughly 40% more than a 1.5 mm shank in the same ring size. Comfort-fit (rounded inside) bands also need a touch more wall than flat inside bands, because the inner curve removes material. We model the comfort fit as a 0.3 mm inner radius and then bump the outer wall so the minimum stays above our minimums. That trade-off is exactly what buyers explore in custom ring CAD to production timelines.

Where thin walls fail in the shop

The first failure mode is casting porosity along the inner wall, because thin sections solidify fast and trap gas. The second is prong heads that go hollow under the seat. The third is long-term wear: a 1.0 mm sterling shank can wear through in two to three years on a daily-wear ring, which is why our ring shank thickness QC check rejects anything below spec before plating. We also flag models that drop below minimums in our CAD file review before the first print, so the designer and buyer agree on the wall before any wax is cut.

How we flag thin-wall models in the CAD review

Before a single wax is printed, our CAD engineer runs a wall-thickness check on every model. We export a cross-section at the thinnest point of the shank, at the basket below the head, and at any shoulder that tapers to a point. Anywhere the wall drops below the material minimum, we flag it back to the designer with a suggested bump. We also flag models where the wall is so thick that the projected weight looks out of line with the market; a 2.5 mm solitaire band reads as premium on screen but doubles the metal cost and can price the ring out of the buyer's target. Comfort-fit bands get special attention, because the rounded inside removes material that a flat-inside band does not. We model the inner radius and then add wall so the thinnest section still clears the minimum. This review step is why our CAD revision rounds stay short: most thin-wall issues are caught on the first review instead of after a casting failure. We also flag any model where a prong head thins to less than 1.0 mm, because a prong that casts hollow will crack when the setter closes it. Buyers receive the cross-section renders so they approve the wall before tooling, not after a sample fails.

FAQ

Why does my CAD read thinner than the finished ring?

Casting shrinkage and then polishing remove 0.1-0.2 mm of material. We model to finished size and add shrinkage compensation, not the other way around.

Can I go thinner on a silver fashion ring that is not worn daily?

Yes, but expect faster wear and a higher porosity rate. We accept 1.2 mm on non-daily pieces and note it on the approval sheet.

Does wide band width change wall thickness?

A wide band (6 mm+) can run slightly thinner wall because the width spreads the load, but not below 1.2 mm in 14K.

How do you show wall thickness to a buyer?

We export a cross-section render at the thinnest point and list the measured wall in millimeters on the quote, so there is no surprise at sampling.

Send us your CAD file and we will flag wall thickness, shrinkage and casting risk before you commit to tooling. Start a custom jewelry manufacturing project with HOLYCOME.