A fabrication order comes in for a plain 2 mm wide 925 silver band, size 7, three hundred pieces. The buyer measures the first sample and finds the wall 1.9 mm on one shoulder and 1.5 mm on the other. The CAD file was correct, the casting was not used (this is fabricated, not cast), so where did the thickness go? On the fabricating bench, that drift is almost always a rolling-mill and annealing sequence that was shortcut on the third pass.
Starting material and why gauge matters
We begin with sterling silver sheet, ASTM B413 equivalent, which per sterling silver convention runs 92.5 percent silver with copper as the balance. For a 2 mm wide comfort-fit band we start from 2.4 mm thick sheet and roll it down to 1.8 mm in the rolling mill. Each pass reduces the gauge by roughly 0.15 to 0.20 mm; pushing harder work-hardens the strip and causes cracks at the edges. Between every three passes we anneal the strip at 1200°F (650°C) until it glows dull cherry, quench in water, and pickle in 10 percent sulfuric acid to remove the firescale. That annealing loop is the step that keeps the strip flat and uniform.
Why the annealing sequence is where bands drift
If a bench tech skips an anneal, the strip becomes too stiff to roll evenly and the mill bites more on one side than the other. That produces the tapered band the buyer measured. The fix is not a heavier file later; it is the annealing loop on the mill. We document the same sequence in silver annealing before soldering sequence, and we tie it to silver soldering flux heat control because the same heat control governs both steps.
Bending on the mandrel
Once the strip is flat, uniform, and pickled, it is cut to length for the target ring size. The length calculation is the mean circumference plus a solder kerf of roughly 0.3 mm. For a size 7 (17.3 mm inner diameter), the mean-circumference strip length is about 56.5 mm. The strip is then bent around a steel mandrel with rawhide mallet, not hammered flat. Hammering stretches one side and produces an oval ring. After bending, the two ends are flushed flat, soldered with hard silver solder, the seam is filed, and the band is rounded up on the mandrel.
Thickness tolerance on the finished shank
We hold the finished band to +/-0.10 mm on wall thickness and +/-0.15 mm on width across the whole shank. That tolerance is tighter than the +/-3 percent we quote on cast pieces, because fabrication gives direct mechanical control. Buyers measuring a reorder should expect the wall to read within that band at three points: top, bottom, and shoulder. If it drifts past 0.15 mm, the strip was not rolled evenly. We cross-check this against finished ring weight tolerance on every run, because a band that is thinner on one side will also weigh less at that shoulder, and the gram weight on the tag will not match the spec.
Comfort fit vs flat profile
A flat-profile band is rolled straight and left flat on the inside. A comfort-fit band is rounded on the inside with a doming tool after bending, which removes about 0.2 mm of material from the inner wall. That difference changes the strip starting gauge: for a 2 mm comfort-fit band we start at 2.6 mm sheet rather than 2.4 mm. Buyers who spec a 2 mm band should tell us which profile, because the starting stock and the weight per piece differ by roughly 10 percent.
FAQ: Silver ring band forming
Is a fabricated band better than a cast band?
For plain shanks, yes on consistency. Fabricated bands hold tighter wall tolerance and avoid the porosity risk that 925 silver casting porosity defects introduce. For detailed or sculpted designs, casting wins.
How many annealing passes does a strip need?
For a 2.4 mm to 1.8 mm reduction, plan on 3 anneals: after pass 3, after pass 6, and after pass 9. Skipping any of them risks edge cracking.
Why does my band show a dark line at the solder seam?
That is firescale from a solder join that was not pickled long enough. We pickle for 5 minutes after every join and cross-check with silver solder hard medium easy flow before moving to polish.
Can you form a band from 18k gold the same way?
The mill sequence is similar but the annealing temperature is lower (1300°F vs 1200°F) and the reduction per pass is smaller. Gold work-hardens differently and cracks more easily at the edges.
If you are specing a fabricated silver band run, send us the width, profile (flat vs comfort), and wall gauge. Our custom manufacturing team will roll, anneal, and bend the first sample against your tolerance before we cut the full lot.
Frequently Asked Questions
What ring sizes can you supply in bulk?
US sizes 5–12 including half sizes. Send a size breakdown with your order and we cast to that curve; comfort-fit inner bands reduce resize requests.
Can I order a mixed size run instead of one size?
Yes. Mixed runs are standard for wholesale: specify quantity per size and we pack and label by size at no extra labor cost.
What is the MOQ for custom ring designs?
50 pieces per design for existing molds; 100–300 pieces when a new mold or CAD model is required.
How should I price rings for retail margin?
Most partners use a 3–4x markup on FOB cost for sterling and 2.5–3x for moissanite solos, which keeps landed cost under 30% of retail.
