How to Use a Forming Mandrel for Jewelry Making
By Pepetools - Precision Engineered Professional Equipment | Published: 2026-10-23
Category: How-to Guides
Learn how to use a forming mandrel to shape open rings and bezels. Step-by-step instructions, common mistakes, and why a flat-back mandrel gives cleaner results.
Quick answer
A forming mandrel lets you shape open rings, bezels, and curved metal pieces by hand or with a mallet. Use a flat-back mandrel like the Rosy Revolver model for precise, repeatable curves without marring your work.
Why use a dedicated forming mandrel instead of a standard ring mandrel?
A standard ring mandrel is tapered and round, which works fine for closed rings but can distort open shapes. A forming mandrel has a flat back that gives you a stable reference surface, so the ends of an open ring meet evenly. This is especially important when you are soldering or setting a stone in a bezel and need the seam to align perfectly.
The Rosy Revolver Flat Back Forming Mandrel from Pepetools is made of hardened and polished steel, graduated with US sizes 1–16, and was designed specifically for open ring forming. Its machined flat surface eliminates the guesswork of holding the piece square against a round mandrel.
How to use a forming mandrel: step by step
- 1. Choose the correct size: Select the mandrel size that matches your target ring size. For open rings, pick a size slightly larger than the finished size to account for springback. Hold the mandrel flat-side down on your bench. Common mistake: choosing a size that is too small and then over-hammering, which work-hardens the metal and makes it brittle.
- 2. Anneal the metal (if needed): If you are working with hard or half-hard sheet or wire, anneal it first so it bends easily without cracking. Hold the piece against the flat back of the mandrel to check that it is straight before you start forming. Checkpoint: the metal should be clean and free of oxides before you shape it, or the surface can get embedded in the mandrel.
- 3. Bend the metal around the mandrel: Wrap the metal around the mandrel, keeping the flat back of the mandrel against your bench. Use your fingers to start the curve, then switch to a rawhide or nylon mallet to tap the metal gently against the mandrel. Work from the center outward to avoid kinks. Common mistake: using a steel hammer directly on the mandrel. This can damage the polished surface and transfer tool marks to your piece.
- 4. Check the seam alignment: Remove the piece from the mandrel and hold it up to a light. The two ends should meet without a gap. If they overlap, tap the longer side gently on a flat steel block. If they gap, bend the piece slightly more around the mandrel. Checkpoint: a gap on the inside of the ring means you need to bend the ends inward; a gap on the outside means you need to open the curve slightly.
- 5. File and finish the ends: Place the ring back on the mandrel with the seam resting against the flat back. Use a fine file to square the ends so they sit flush. Remove the piece and sand the ends with 400-grit sandpaper before soldering or setting. Common mistake: filing while the ring is off the mandrel, which can round the ends and create a visible gap after soldering.
Product facts
- "Rosy Revolver" Flat Back, Open Ring, Forming Mandrel: Manufactured at the request of Jessica Jordan Coté of Rosy Revolver. Graduated with US sizes 1–16. Flat back machined surface for open ring forming. Hardened and polished steel. Made in USA. The flat back acts as a built-in straightedge, so you can file or sand the ring ends flush without needing a separate block.
"Rosy Revolver" Flat Back, Open Ring, Forming Mandrel
