The cutting arm (PROSE: Dalek Survival Guide) was a cutting tool form of the manipulator arm, which was used by the Daleks in the place of the conventional sucker arm to cut through metal. (TV: The Daleks)
On Spiridon, they used one to cut through a thick door. (TV: Planet of the Daleks) On locating Lynda Moss, a group of Time War-era Daleks used their flames to cut through a metal door on Satellite Five, which was meant to be reinforced against meteors, though Lynda doubted the "Earth workmanship". (TV: The Parting of the Ways)
In an alternate timeline in which they invaded Urbinia, one Dalek suggested using a cutting flame to breach the spaceport hangar bay in Kiria City, but another decided they would use hostages instead. (AUDIO: Daughter of the Gods)