Yes, as long as the sizing is within a 0.25 (1/4) to 0.5 (1/2) ring size and there are no settings with stones in place.
If you need to size a ring up higher than this amount, it is best to seek help from a jeweler who can insert a section of metal into your ring seamlessly.
To size a ring up within the 0.25 - 0.50 ring-size range:
Place the ring onto a steel ring mandrel
Using a raw-hide mallet, tap the ring down the mandrel, striking the ring a few times
Rotate the mandrel and repeat all the way around the ring, so you are stretching the ring equally around the band
Remove the ring from the mandrel, flip it over and repeat this all the way around the ring again, so you have sized the ring equally from both sides of the ring--not stretching it more from one direction than the other
To size a ring up within the 0.25-0.50 range with a stone in place, be sure to use the ring stretcher that is suited for this task.
- Tammy Honaman, Author, Jewelry-Making Expert and Educator