MJSA. Professional excellence in jewelry making and design.

Social Media Roundup:
Mandrel Madness

MJSA’s LinkedIn Group discusses the problem of non-standard mandrel sizes

By Peggy Jo Donahue
Originally published March 2013

The Catalyst

Mandrels and Ring SizersTom McLaughlin, goldsmith/designer at Lennon’s Jewelers in the Syracuse, New York, area, recently posted a question asking how he could find mandrels that were all uniform. “Currently we have five mandrels in our shop,” he said, “all registering different sizes—a 6 [on one] is not always a 6 [on another]. We work around it, but it would be nice if I could get them all to match. I have seen calibrated sets that include the ring sizers to match the mandrel, but I believe the mandrel is made of aluminum and would not stand up to the beating a mandrel endures in a shop. Does anyone else experience this? If so, how do you work with the inconsistency? Thanks so much for any input you may have!"

The Conversation

“This is an issue we deal with every day,” says Mathew Ego, director at Unique Settings of New York, in the Greater New York City area. “It is staggering how many different mandrels are out in the market, especially with retail stores. We actually CNC our own mandrels in house, for quality control [purposes]. This has solved the issue in-house, but not when delivering the product to the retail market. So, we have started to size all our rings to sit just above the size marker instead of in the center [of it], since it is always easier to size a ring up than down. Almost any jeweler in a retail store can use a ring stretcher or polish out the inside if need be. We have also developed training diagrams for our retail clients, which have been printed in all our catalogs. With these new efforts, we have decreased the number of returned or exchanged items due to finger size. It seems to work,” says Ego.

“This was a huge problem when I worked at Overstock,” remembered Sherene Casanova, who is now a gemologist from Salt Lake City, Utah. “Our partners were all using different brands of mandrels, and they could be 1/4 to 3/4 size off [from] our mandrels. We spent a lot of money trying to get standard mandrels for our returns processors, our gemologist graders, and our partners. We finally chose a brand and notified all the partners that they needed to purchase this brand and model so we could be as close as possible in size.” However, she added, in the end none of the mandrels were exactly the same, so questions still sometimes arose. “The processors would have to bring the ring in question to my boss or me, and we would make the final decision based on our mandrels, which did match exactly to each other,” she said.

Others had more luck with getting uniform mandrels—Philip Edwards, owner at Edwards Custom Jewelry and Repair in Alexandria, Louisiana, said he “ordered all the same [steel] mandrels, as well as a plastic and an aluminum mandrel, along with ring sizers, all at one time from [one company] and they all matched.” And Ted Doudak, CEO at Riva Precision Manufacturing in Brooklyn, New York, recommended that any mandrel that doesn’t meet specific standards be rejected: “Do not let any mandrel enter your shop until you approve it and inscribe on it your mark. Anything else, throw away.”

He and others also noted that even good mandrels lose accuracy with time. “As you use a working mandrel, it will tend to change size, due to the pounding, filing, etc., that goldsmiths do,” said Wayne M. Schenk, a bench jeweler at Michael’s Custom Jewelry in Visalia, California. While Doudak recommended keeping a record of the diameter of each mandrel—“this will give you the comfort you need, and isolate those that have changed over time”—Schenk suggested using two sets of mandrels: “One to work with and pound on, the other as an umpire."

Jo Haemer agreed. “I use both a marked and an unmarked mandrel,” said Haemer, owner of Timothy W. Green in the Portland, Oregon, area. “I use an old marked mandrel that I know is accurate. I use an unmarked one to hammer, and polish on. Thus I have no sizing lines inside a shank that I have hammered on and my marked mandrel stays true."

Schenk also noted the need to ensure that not only mandrels, but ring sizers, were calibrated. He suggested making “a set of calibrated sizing rings to match any mandrel you already have. This is a wonderful project for an apprentice as it teaches the value of quickly and accurately sizing a ring.” [Editor’s Note: Jeweler and educator Brad Simon from Spartanburg, South Carolina, once shared another tip in the pages of MJSA Journal. He recommended purchasing several pairs of plastic ring sizers, organizing them by finger size, then tossing the correct sizer into the job envelope along with the ring. Then, the bench jeweler could make sure the ring was exact, by fitting the actual sizer used with the customer onto the ring mandrel.] 

As important as the need for calibration, several participants noted that it wasn’t the total solution for ensuring proper sizing. “Another important area for ring sizing is defining how to measure it,” added Jose Cortorreal, who is the finishing department manager at Riva Precision Manufacturing. “A standard practice in the industry is to divide the shank width into two categories: 7 mm or less (shank width) means the starting point is the bottom leading edge; 7 mm or more (shank width) means the starting point is the centerline of the shank.”

“The key is to keep the client informed” about your sizing method,” said Daniel Grandi, president and owner of Racecar Jewelry Co. Inc. in Pawtucket, Rhode Island. “Perhaps the best way [to do this] would be to create a small flyer that can be e-mailed or put in the package explaining how your rings are sized. There should be a simple standardization of ’how to measure,’ using one method only—then everyone is on the same page.”

He added that “if anyone is producing a large quantity of rings for a client, perhaps you should send the client a mandrel that matches your factory ones. Engrave your factories name on the handle, or your initials, so the store clerk will know which one to use [when selling your rings].”

Several contributors to the conversation mentioned the need for every jeweler to use one worldwide standard for ring sizing. The International Organization for Standardization (ISO) does have such a standard (ISO 8653:1986, “Jewellery—Ring-sizes—Definition, measurement and designation.”). This standard defines standard ring sizes in terms of the inner circumference of the ring measured in millimeters. Unfortunately, as several jewelers pointed out, the ISO standard is not uniformly used by Americans, perhaps because American ring sizes don’t translate exactly into millimeter sizes.

Paul Finelt of Resource Shift, a jewelry manufacturing consultant in the New York City area, who is an engineering and metallurgy expert, offered a final set of instructions for a company to use in creating and maintaining reliability in ring mandrels:

• Do not use aluminum, plated, or unhardened mandrels in manufacturing. They are retail tools only. (To determine if your mandrel is hardened, recommends Finelt, “grind the end of the mandrel—if you can dig in deep it’s probably soft. Some hardened alloys will also spark more heavily when ground than others, but that is a relative measure.”)

• Inspect every mandrel that is purchased to ISO 8653:1986, by measuring the diameter at three finger size locations (size 0, size 6, size 12), using a digital caliper.

• As an alternative, purchase/make ring gauges at these same sizes (size 0, size 6, size 12). "These gauges are easier & faster to use than a caliper," said Finelt.

• Reject / return any mandrel that is off by more than /- .003" at any two locations.

• Mark the ends of your accepted mandrels with a company and/or inspector’s mark using a permanent marking method. Engraving with a rotating stone will work on a hardened mandrel. "Use protective eyewear," advised Finelt. "Sparks will fly."

• Re-inspect your mandrels annually. Even hardened mandrels get severely abused.

To join this and other MJSA discussions on LinkedIn, click here.

MJSA Advantage

MJSA members receive exclusive informational and marketing benefits, from free promotional placements to information research services.