How to enlarge a ring with a mandrel

Written by cathy williams
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Enlarging a ring with a mandrel refers to stretching the shank, or the section of the ring that hugs the finger, using a small, graduated cylinder made of steel known as a mandrel. Most mandrels used for jewellery are calibrated and will indicate ring sizes in ascending order to use as a guide when enlarging a ring to a desired size. Enlarging a ring with a mandrel is a method of increasing the size of a ring without adding additional metal to the ring shank.

Skill level:

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Things you need

  • Ring sizer set
  • Steel mandrel
  • Vice
  • Rawhide mallet

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  1. 1

    Measure the desired ring size using a ring sizer on the finger you wish to place the ring.

  2. 2

    If the mandrel is not calibrated and does not indicate ring sizes, place the appropriate ring of the ring sizer on the mandrel. Once the ring will no longer move down the mandrel, use a pencil to make a line at the bottom of the ring shank.

  3. 3

    Place the handle of the mandrel vertically in a vice. Tighten the vice until the mandrel will not move when struck.

  4. 4

    Slide the ring to be enlarged down the mandrel until it can't go any further.

  5. 5

    Tap all the way around the ring lightly with a rawhide mallet until the ring stretches halfway to the ring size marking on the mandrel.

  6. 6

    Remove the ring from the mandrel, turn it over, then place the ring back on the mandrel until it can't go any further. Tap all the way around the ring lightly with the rawhide mallet until the bottom of the ring shank reaches the desired ring size mark.

  7. 7

    Remove the ring from the mandrel and try it on. Place the ring back on the mandrel and tap it lightly two to three times if minor adjustments need to be made.

Tips and warnings

  • Enlarging a ring on a mandrel should be a slow process if desired results are to be achieved. Since the process to enlarge a ring is more simple than the process to make it smaller, it is essential that you lightly tap the ring shank with the rawhide mallet and remove the ring and try it on frequently when making minor adjustments to avoid making the ring too large.
  • Rings with stones should not be enlarged using a mandrel as the process can damage the setting or stone. Enlarging rings with mandrels causes stress to the ring shank and will cause it to crack if the size adjustment is too great.

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