1378869 Countersinkers A KNUTSSON 23 Dec 1971 [29 Dec 1970] 59872/71 Heading B3C A countersinker assembly for attachment to a spiral fluted drill comprises a holding device 3 having an axial bore to accommodate the drill 1 and which is divided longitudinally into two halves, the ends of the holding device being conically formed, a countersinker 4 having cutting edges 6 and an internal conical surface to fit one end of the holding device 3, and a collar 2 internally conically formed to fit on the other end of the holding device, the countersinker 4 and the collar 2 having co-operating screw-threads enabling them to be screwed together to urge the holding device into gripping engagement with the drill. The holding device halves include swarf excluding elements 5 which are flexible to allow riding out of the drill flutes when relative rotation occurs through slipping between the countersinker assembly and the drill. The cutting edges 6 include an edge 10 extending into the drill flutes to prevent relative slip.
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