Check Your Tools
Ring mandrels can differ in sizes by as much a ¼ size, and so mandrels used at the take-in counter should be identical to the mandrels used at all the benches. In addition, they should match the ring sizers used to measure the customer's finger. Do not blame the bench jeweler for missing a size when the problem may be the tools!
There are two reasons for the difference in the sizes.
- Economics
When a manufacture makes a standard ring mandrel, the small end, and the large end are measured. If these measurements are correct, it is assumed that the rest is correct. A “precision” mandrel is available from some companies. These mandrels are checked with a master gauge at each size. - No Legal Standards for U. S. Ring Sizes
The National Institute of Standards and Technology (formerly the National Bureau of Standards) has no standardized ring sizes. The Federal Register and Federal Trade Commission also have no ring size guidelines. American ring sizes are more a matter of tradition rather than any legal standard.
To help eliminate discrepancies caused by using inaccurate ring mandrels
- Buy only the more expensive “precision” mandrels and buy them all at the same time from the same supplier. The extra cost is justified by avoiding having to re-size just one ring.
- Check all ring sizers used in the store against the precision mandrel, then have your bench jeweler adjust the ring sizers to match the mandrel. (Or, better yet, have your bench jeweler make a set of ring sizers from brass sample ring bands with the new mandrels. Stamp or engrave the ring size on the outside of the band and keep the set at the counter in a ring tray.)
- Purchase inexpensive plastic ring sizers and after finding the one that fits the customer's finger, include it in the job envelope. The jeweler can size the ring to the plastic sample. This works well when sending the job out to a trade shop or manufacturer.
Measuring Ring Sizes
First measure the ring’s size by sliding it firmly down onto a ring mandrel; look down the mandrel to be sure the ring is in contact with the mandrel all the way around. Then read the measurement of the ring at the point where its shank first touches the mandrel. See diagram.
If the ring has a large stone, measure the ring on a grooved ring mandrel. Carefully slide the ring onto the mandrel with the stone over the groove. Sliding the pavilion of the stone against the hard steel mandrel may damage the ring or cause the stone to chip, break, or pop out of the ring.
Measuring the Customer’s Finger
To determine what size the ring needs to be, measure the customer’s finger with the appropriate ring sizer: wide for rings with shanks wider than 4 mm, narrow for all others.
Keep trying until you find the ring sizer that fits the finger comfortably, slides gently over the knuckle with slight resistance, and needs only moderate pressure (never force) to put on. When you find what seems the best size, it is a good idea to try the next size for verification.
A large ring with a heavy top needs to fit a little tighter to keep it from turning on the customer's finger. Hollow rings open to the finger will fit looser than rings that are solid on the inside; they should be sized one eighth to one fourth size smaller than the ring sizer that seems to fit.