Any tool at Harbor Freight should be considered 100% disposable. It may work for one use or break before it even finishes that job (was that too harsh?).
I have a crappy set of taps that I bought from a similar place. Yes, they cut soft steel fairly well, but the tool steel is so brittle that it has fractured over just a few uses (little flakes break off).
I don't recommend a $100 full set of taps either. Find the ONE size that you need and buy a decent tap. The big box home stores should have one or Ace/Sears.
One tap that works well is far more useful than a case of not-so-good quality taps of lots of sizes.
My 2¢.
faz