I sound like a broken record, but here goes: Mortgage rates have hit record lows, yet again.

Which raises an intriguing question: Does it make sense to use a refinancing to raise cash to invest in other ways, or to hold as a reserve?

For some people, it might — if the costs and risks are weighed.

The average rate for 30-year fixed rate mortgages fell two weeks ago to 5.57 percent from the previous week’s record of 5.65 percent, the Mortgage Bankers Assn. said. The rate on 15-year fixed mortgages also hit a new low, 4.9 percent, vs. 5.02 percent a week earlier.

Obviously, this is a great opportunity to refinance a high-rate mortgage, thereby reducing your monthly payments or cutting the time it will take to pay off your loan.

Of course, many homeowners are going farther by taking out new loans that are bigger than the ones they’re paying off. Indeed, economists say hundreds of billions in home equity has been converted to cash through refinancings, giving consumers the spending money that has kept the economy from sinking further.

It’s silly to take on a 15- or 30-year debt just to buy a fancier car or eat out more often. But suppose you want to use that money for an investment?

Some have advocated this all along, arguing, for instance, that it would pay to borrow against your house at, say, 7 percent, in order to invest in stocks, which have returned about 10 percent a year over the long run.

But that would seem awfully risky in today’s shaky stock market. If you’d taken $50,000 out of your house a year ago and invested it in a stock fund that mirrored the broad market, you’d have only $36,500 today. But you’d still be making payments on that $50,000 loan. Ouch.

Similarly, it probably would be too risky to invest in long-term bonds right now: Since bond yields are so low, the odds are better they will rise than fall.

For example, if you put $50,000 into 10-year U.S. Treasury bonds, you’d earn about 3.6 percent, or $1,800 a year. Had you raised the $50,000 with a 4.9 percent 15-year mortgage, the first year’s interest charges would come to about $2,400. (4.9 percent of $50,000 is $2,450, but interest charges would be lower because some principal would be paid off each month.)

With this approach, you’d pay only $600 more on the debt than you’d earn in interest, not a big price to pay to keep that $50,000 in reserve. Unfortunately, you might have trouble getting your $50,000 back if you needed it before the bonds matured in 10 years.

If interest rates on new bonds rose by, say 2 percentage points, no one would pay $50,000 for your old bonds. In fact, if rates jumped soon after you bought, you wouldn’t get more than about $40,000. Ouch again.

To avoid the risk of losing principal, you could put the $50,000 into a savings account or money market fund. You’d only earn 1 percent or so, but your cash would be safe and instantly available for investment. That might be worth it if you believe rates will rise or stocks will offer good opportunities sometime soon.

Or consider this: You could use the $50,000 to buy a five-year certificate of deposit. Top CDs are paying about 4 percent. This way, you’d have no risk of losing principal, as you would with stocks or bonds. And the CD would earn about $2,000 a year, paying all but $400 of your interest charges on the $50,000 mortgage.

If you saw a better investment opportunity later, you could redeem the CD early to get back your cash. Doing so would trigger an early withdrawal penalty on the CD, typically equal to the last six months’ interest earnings — $1,000. But that loss could quickly be made up if new CDs then were paying 5 percent or 6 percent. Be sure to check the penalty before investing, as some are much higher.

Other factors would have to be weighed, such as the refinancing fees you’d be charged. But with rates this low, the cost of taking money out of your home is not very high, so long as the cash is put to a money-making purpose.