Like a once-in-a-lifetime ride on a time machine, mortgage interest rates are taking borrowers on a sojourn six decades back to the early 1950s, experts say. Rates are now the lowest in generations.

And with the Federal Reserve Board’s relentless effort to push interest charges lower and lower, home buyers and homeowners seeking to refinance are seeing benchmark 30-year fixed-rate mortgages breaking the 4 percent barrier — a 60-year low.

Fixed mortgage rates have been inching lower throughout the summer, sending 30-year fixed loan averages in Freddie Mac’s Primary Mortgage Market Survey to levels borrowers hadn’t seen since the early 1950s.

In mid-September, Freddie Mac’s survey showed mortgage rates — both fixed and adjustable — hitting all-time record lows amid market and employment concerns and economic uncertainty.

Thirty-year fixed-rate mortgages averaged a record low of 4.09 percent on September 15, down from 4.12 percent a week earlier. Last year at this time, the 30-year fixed loan averaged 4.37 percent.

“The great opportunity now is for home buyers to get a mortgage at a historically low rate,” said Marc L. Kramer, senior residential lender for Wintrust Mortgage in Chicago. “Freddie Mac reported mortgage rates set new record lows, buyers shouldn’t expect further rate dips. Lenders are seeing plenty of loan volume, so they don’t have to lower pricing to get more activity.”

A spot check of Chicago-area lenders in mid-September showed that several were quoting 3.875 percent on 30-year loans, with down payments ranging from 5 percent to 25 percent.

For the week ending September 15, Freddie Mac reported lenders were charging the following average rates on various types of loans:

“Continued investor concerns over the state of the European debt markets kept U.S. Treasury bond yields low and allowed mortgage rates to ease once more this week,” said Frank Nothaft, vice president and chief economist, Freddie Mac.

In comparison, the average interest rate of outstanding mortgages nationwide in the second quarter was 5.28 percent. By refinancing into today’s 30-year fixed mortgage, homeowners could shave almost $1,715 a year in interest payments on a $200,000 loan, Freddie Mac said.

“Apart from just fixed-rate mortgages, various other interest rates are at or near all-time historical lows as well,” Nothaft observed. “Both the 10-year constant-maturity Treasury bond and AAA-rated seasoned corporate bond yields were at 50-year lows over the week ending September 9th.”

However, the world of mortgageland is unpredictable and volatile. Few of today’s novice borrowers remember that only 12 years ago in August of 1999, lenders were quoting 8.15 percent on a 30-year fixed mortgage.

By June of 2003, the benchmark 30-year fixed rate average had fallen to 5.21 percent. However, beginning in mid-2004, the Fed methodically raised short-term interest rates 17 times over a period of two years. The series of quarter-point interest-rate hikes were designed to make sure inflationary pressures remained under control.

The Fed paused its rate-tightening campaign in June of 2006, and in mid-July the average rate peaked at a lofty 6.74 percent. Rates have seesawed ever since.

To appreciate today’s historically low rates, housing experts say home buyers need only to look at what banks and mortgage lenders where charging in the early 1980s.

According to Freddie Mac, benchmark 30-year fixed-rate mortgage rates peaked at a whopping 18.45 percent in October of 1981 during the last great recession. Rates fell below 10 percent in April of 1986, and then bounced in the 9-percent to 10-percent range during the balance of the 1980s.