A method of microdeburring a selected portion of bore in a workpiece with a jet of abrasive gas is provided that is particularly applicable to the removal of microburrs at the interface between the timing and metering spill ports in a fuel injector metering barrel and the plunger bore. In the method, the nozzle that emits the abrasive gas is first inserted in and aligned with the bore so that the jet is focused on the microburrs at the interface. The nozzle is then actuated for a time period long enough for the jet to remove the microburrs from the bore, but insufficient for the jet to cause unwanted radiusing of the bore at the interface that could degrade the timing characteristics of the fuel injector. The method also includes the step of interposing a shield within the metering barrel to mask off the finished surface of the barrel from unwanted abrasion. The use of a gaseous, as opposed to a liquid carrier, in combination with the precise alignment of the jet and use of an abrasion shield in the workpiece, results in a precise elimination of unwanted microburrs that is unaccompanied by unwanted widening or radiusing of the ports at their interface with the plunger bore.