Every weekday morning at 7:15, Frank Roome boards a blue bus marked "Zephyr" that takes him and 20 other inmates from the Kansas Correctional Institute to a sheet-metal factory owned and operated by Zephyr Products Inc. in the town of Leavenworth, 2 1/2 miles away.

Unguarded in the bus, which is driven by another inmate, Roome (pronounced Rome) and his fellow prisoners are on the job at 7:30 every day at Zephyr, where they're involved in a unique prison experience.

They go unguarded at the factory all day, kept on the job by a program that pays them $31 a day, plus a $2-a-day bonus for good attendance, plus stock options every three months they're on the job, and teaches them a skill that earns them as much as $90 a day after their release.

These inmates don't make license plates, the traditional products of prison work programs. These inmates work for a private industrial firm producing sophisticated metal parts for missiles, radios, television sets and self-propelled combines.

Their customers are not agencies of the state that put them in prison. Their customers are Western Electric, Stewart Warner, Allis Chalmers, the U.S. Postal Service and the Pentagon.

The Minnesota and Arizona penitentiaries have similar work programs in private industry for prisoners, but the Kansas program is the only one outside the prison.

Now in its 20th month, the Zephyr program appears to be working. Inmate productivity is as high as it is in industry, and absenteeism is lower. Of the 12 inmates who worked at Zephyr who've been paroled, 11 are working at sheet metal plants elsewhere in Kansas and are leading productive lives. One is back in prison, a welder who kidnaped two women after his parole. More important, no inmate at Zephyr has started trouble on the job, and no inmate has tried to escape, even though doing so is as easy as walking through the factory's big double doors.

"It hasn't happened, probably because of peer pressure and the losses that would be involved," Roome said the other day on the factory floor, where he serves as plant manager. "In our society, you're a person if you produce something, if you contribute to your family. That's what's happened here. These people are not just burdens, they're members of their families again. This program has given these inmates back their sense of identity."

The inmates in the Zephyr program are not people guilty of passing bad checks. Of the 20 inmates on the Zephyr floor the other day, eight were in for murder. Roome is there for second-degree murder, a crime he committed when he was drunk after a messy divorce at the end of a year of combat as an infantry captain in Vietnam.

Roome tells of the time he interviewed a steel salesman in his office at Zephyr. "The salesman leaned forward and said, 'Do you know there are murderers working here?' " Roome said he leaned even closer and whispered, "You're sitting two feet from one of them."

The inmates imprisoned for murder say they feel they would lose too much if they tried to escape while working at Zephyr. One said, "With the money I've got in my savings account from working at Zephyr, I can't afford to escape."

Listen to John Hensley, a strapping 38-year-old imprisoned since 1974 for killing a man he caught with his wife, and who doesn't come up for parole until 1989:

"This has been good for me. I've kept up my payments on my house, and it's got me out of prison all day long for the last year and a half. I have three daughters and a mother, and I want to go home, but I want it all to be legal."

Ruby Marshall, 35, used to work in a factory making womens' coats. Now she stamps out holes in strips of sheet metal. She is in for first-degree murder, and won't see a parole board until 1994.

"I have a little boy to take care of, and before I came here I didn't have any way of helping him. I feel like a human being at Zephyr. Why would I want to mess that up?" she said.

Across the factory floor from Marshall works Danny Bailey, 32, a prisoner since he was 19, when he murdered a man in an argument.

"I been locked up 13 years, and until I got here I never had the opportunity to get me a job skill," Bailey told a visitor. "Why don't I walk away from here? Because I'm eligible for parole in two years and I've got too much to lose. Besides, I don't want to mess up this program for everybody else who's worked so hard to make it go."

Besides teaching them a skill and getting them out of prison every day, the Zephyr program pays the inmates the minimum wage of $3.35 an hour, money they're forced to save or send home. In Kansas, most prisoners of the state are paid 90 cents a day for their work and $250 "gate money" when released. Says Roome: "That's enough to buy you a bottle and a gun."

Roome has managed to save $2,000 since he began working at Zephyr, which is typical of the Zephyr experience. Danny Bailey has sent more than $1,500 home to his wife, who moved to Leavenworth when he was put into prison at Lansing. Richard Primm, a welder who will be paroled Oct. 1 after serving five years for armed robbery, has saved enough to buy a car when he gets out.

"It gives you a fresh start," said Primm, who's been offered two welding jobs on the outside. "Leaving here with $2,500 instead of $250 is a big difference."

Zephyr is the brainchild of a Harvard Business School graduate, Fred Braun, who brought the idea of employing prisoners in his factory to Kansas Corrections Commissioner Patrick D. McManus two years ago. Trained in Minnesota, where a computer company has employed inmates inside prison walls, McManus grabbed the chance to try it outside the walls for the first time.

"It's worked magnificently, better than we ever hoped," McManus said while walking a visitor across Zephyr's factory floor. "We started out with a guard on the floor, then dropped him because he had nothing to do. The inmates have performed superbly."

On McManus' urging, Braun located the Zephyr plant in Leavenworth. The city sold bonds to build the $500,000 plant, which it leases to Zephyr. Long accustomed to being a prison community, the people of Leavenworth felt no discomfort living near a factory run by prisoners.

Down the road less than three miles, the dome of the famous federal prison named for the town looms over the landscape. Leavenworth is the only federal prison with a dome shaped like the Capitol dome to remind entering prisoners that they have committed a crime against their country.

Having prisoners work for private concerns is not new. Nineteenth Century inmates were often leased to logging companies and to southern plantation owners to replace freed slaves. In those days, though, the inmates were paid nothing, and by the 1920s most states prohibited the practice because of scandals involving excess profits and brutal conditions.

When the Depression came, the labor unions got Congress to ban from interstate commerce products made by inmates. The ban was suspended during World War II, but was reinstated by President Truman in 1947.

At the same time, states passed laws barring inmate products on the open market. Union pressure has prevented inmates from working in their own prisons, once keeping inmates in Pittsburgh from painting their own cells.

Two years ago, Congress passed an amendment sponsored by Sen. Charles H. Percy (R-Ill.) to the law banning inmate goods from interstate commerce. It authorized seven prison industry projects, provided the prisoners were paid the minimum wage, which would be subject to room and board charges, taxes and family support payments. Arizona, Minnesota and Kansas took Congress up on the idea, but only Kansas put its project outside the prison walls.

Kansas is careful about which prisoners it puts to work outside the walls. Only "minimum-security" prisoners are screened for the jobs at Zephyr, which means only prisoners who've been on their best behavior for at least a year.

Why does Kansas approve murderers for the Zephyr jobs?

"Murderers are often your best risks," Corrections Commissioner McManus said. "They're in prison because they found themselves in a situation they couldn't handle, not because they're hardened or habitual criminals. It is often the only crime they ever commit."

The screened prisoners are screened a second time by Zephyr officials, who hire people they believe want to work. Henry Zahn, executive vice president of Zephyr, said, "If he wants to work, I like that. If he's energetic, I like that too. I also look for somebody who is not a bum check writer or a repeat criminal. They need more help than I can give them."

Zephyr hires inmates with at least a year left in prison, preferring a mix of prisoners whose sentences average 30 months. Money is the motive for that move. If Zephyr has to train an inmate, it wants to get its investment back. If an inmate is already skilled, it wants to get the most out of him.

The first year it operated with prison help, Zephyr lost $86,000. Seven out of the last eight months it turned a profit. So far this year, the ink on Zephyr's books is $25,000 in the black. With new contracts on the way, Zephyr is looking to increase its profits and hire at least 15 new inmates to handle the business.

If it all sounds too good to be true, Kansas prison officials look to the day when not everything is so rosy at Zephyr. They worry about the day when labor unions seek to organize the Zephyr prisoners, when competitors start to complain about the cost advantage that Zephyr has when bidding on sheet-metal contracts and when the prisoners complain about working too long for the minimum wage.

"I think the inmates will recognize that as they learn more skills they ought to be paid more," McManus said the other day. "I think it's inevitable that some things are going to have to change."