Ring Stretcher Size Enlarger Jewelry Sizing Tool Rathburn Wedding Bands Sizer Rathburn Ring Stretcher For Resizing Rings. This is a new Rathburn ring stretcher. It can quickly enlarge plain bands. Simply tapping the end spreads the outer mandrel and stretches the ring. This is used for wedding bands size 8 to 15. A Ring Stretcher, a basic way to enlarge jewelry rings, is the most economical and simplest method to stretch rings and it is easy to use. The Rathburn fixture consists of 2 parts, a steel Collet Multi-Stepped Mandrel and Tapered Pin Expander. Place the ring on the stepped collet, choose the size that the rings fits onto, then place the expansion collet on the wooden base. Now insert the Tapered Pin Rod and gently tap the tapered steel Pin by using a mallet or hammer (light Impact). Make sure not to oversize the ring, and cause it to break apart. Mandrel can be removed by simply tapping the opposite end. Note: Care must be taken whenever stretching a ring. Tool is not to be used with stone set rings, thin shanks, inspect for any solder joints that may break apart when stretching. Tool works well with Bands, may need to anneal to soften the ring to afford expansion of the metal. Generally this tool fixture will not expand more than 1 finger size.