@ronv
Not all op amps can go all the way to ground. The two you have listed cannot. When the + input is ground the output will still be about 1.5 volts.but the opamp's non inverting i/p reaches ground when pot knob is turned down ? effectively the opamp o/p should go to something that makes sense resistor voltage = ground also.....
Don't forget the resistor in the output of the op amp or it may oscillate.i have chaged the schematic as per suggestion, please see.