Stone cutting tool for holes with enlarged bottom - has two swinging blades which open out predrilled hole

摘要

The tool for making holes in concrete, stone, brickwork etc. so as to produce an enlarged diameter part of the hole near the bottom can be used with a rotary or impact drill, and is inserted in a predrilled hole. This tool has a shank (16) and a nose (24) the same dia. as the hole, and between them two cutting blades (22) which drill out the larger dia. portion. The shank is shouldered (14) to form a yoked base (18) and between them is a pin (32) passing through a sloping slot (34) through each blade. The nose has a similar yoke (26) with a pin (28) acting as a pivot for the two blades. The shank carries a helical groove (38) for removal of material.