Abstract: Burrs on flame-cut semi-products are removed with the aid of a transversely guided flat chisel driven pulsatingly by a pneumatic percussion device, which reduces the advance forces required. The inclination of the flat chisel may be varied during operation against a continuously effective force to permit the chisel edge to follow any uneven areas, e.g. cambers, which may be present on the product surface bearing the burr, and to cause the chisel edge to always engage between the product surface and the burr. A variable speed drive is used for relative advance movement between the chisel and the product, so that the advance speed is increased when a portion of the burr splits off and gives way during chisel operation.