The commercial revival of vinyl records is good thing for many people: record labels, recording artists, audiophile collectors, independent record shops — all for whom the increase in sales each year is considered a jolt of life in what otherwise is considered a growing public disinterest in owning tangible music.

But for Matt Earley, more people wanting more vinyl records presents a problem: The six presses that make his records at Gotta Groove Records in Cleveland are more than 40 years old, which means extra shifts and increased production is a recipe for potential disaster, especially when orders are lined up for months.

“It keeps me up at night,” he says. “My biggest worry is what is going to break when, not if it will break. Everything breaks.”

His is one of only about a dozen or so record pressers left in the United States, and they all face the same challenge: locating, refurbishing, installing, operating and ultimately repairing machines that are no longer made but are pushed harder and faster than they were in their heyday.

“If you run a press 24 hours, six or seven days a week, there is one rule of thumb: You are wearing the machine out twice as fast,” said Bob Roczynski, president of Record Products of America, a 38-year-old company in Hamden, Conn., that is one of the last in the United States that supplies machine parts to the existing plants in operation today.

The current refurbished machine stock was originally designed to run eight to 10 hours a day for one shift, he said. Today, many plants report that demand is forcing their machines to run three shifts up to six days a week.

This is a boom time for vinyl. Between 2007 and 2013, U.S. vinyl sales increased 517 percent to 6.1 million units, according to SoundScan, and that doesn’t include overseas demand or sales made directly from record-label websites. While CD and digital music sales still dominate music sales, both have taken hits due to streaming; sales for digital decreased for the first time last year.

Vinyl is all they sell at Third Man Records in Nashville. In fact, “Lazaretto,” the current solo album by founder Jack White, set the U.S. record for the biggest-selling vinyl record of any year since Pearl Jam in 1994. Ben Blackwell, in charge of overseeing Third Man’s vinyl production and distribution, said combined U.S. and overseas pressings have already topped 100,000 copies.

“The thing will not stop selling,” he said. “That record has been on the press since the beginning of May and it hasn’t come off the press since.”

White is an avowed vinyl fetishist: Most Third Man records receive special colored, or multicolored pressings; his newest is the ultimate feat. It includes two hidden tracks beneath the label that play at different speeds, one side plays from the inside to the outer rim, and it also features a hologram that appears when the needle is placed in the “dead wax” area.

To make that happen, the label tapped United Record Pressing in Nashville, one of the nation’s oldest record plants, dating to 1949. The company has announced a $5.5 million expansion, adding 16 to its current stock of 22 presses, which are currently running 24 hours a day, six days a week, producing up to 40,000 records daily.

But expansion comes at a price. There have not been any new record presses manufactured since the early 1980s, and the cost to do so is prohibitive. Roczynski has calculated that a new machine would cost about $130,000, while others say that price could be doubled.

“No one is going to pay it,” he said. Which means that plant operators are left to hunt for “anything out there that is left in mothballs or storage or rusting away someplace.”

That scenario has created a global treasure hunt for presses. United said its expansion was made possible because it had planned ahead, stockpiling old presses over several years. Other plants say word of mouth, good luck and a large bankroll have led them to their finds, usually abandoned presses left dormant once CDs took hold and became the dominant format.

“It’s just like anything else — the harder you look, the more you are willing to spend, the easier it becomes,” said Chad Kassem, founder of Quality Record Pressings, a plant in Salina, Kan., that manufactures audiophile-quality vinyl for reissue campaigns for bands like Pink Floyd, the Doors, Jimi Hendrix and others.

Kassem has been operating a premium vinyl retail business called Acoustic Sounds since 1990, but in 2011 he started manufacturing his own records because he was tired of waiting in line four to eight weeks and not being in control of managing the quality of his product.

“I needed my records as soon as possible and I needed them the highest quality as possible,” he said. About $2 million is now invested in a 21,000-square-foot plant that was once a food storage facility. “A wise man would pause” at such an endeavor of retrofitting such a space for making vinyl records, he admitted. “I’m just crazy.”