The diamond hollow drill with an external thread (Continental) R ½ inch is made of steel covered with protective lacquer and a diamond coating of sintered material.
        Application note:
        The drill bit must be sharpened before first use! 
Select the correct speed 
Drill bit speeds: ø 3-4 mm = 4000-5000 1/min - ø 5-15 mm = 2000-3000 1/min - ø 16-25 mm = 1500-2000 1/min - ø 26-50 mm = 500-1500 1/min - ø 51-100 mm = 300-800 1/min 
o Speed too low: The bond between the diamond grains is not sufficiently removed, the drill bit becomes blunt and must be resharpened with a sharpening stone (BO 5000499 / BO 5000499B / BO 5000499L).
o Speed too high: The diamond grains can be torn out of the bond.
Ensure cooling 
o Diamond hollow drills require internal water cooling - external cooling is not sufficient. 
o For deeper drill holes, lift the drill at short intervals to flush out the drill hole. 
Adjust water pressure 
o The required water pressure depends on the drill diameter. 
o Without adjustment, the back pressure increases with increasing diameter and makes the feed more difficult. 
Reduce tool wear 
o The coolant Bohle Vetrocool (BO 5002827 / BO 5002828) lowers the drilling forces and reduces tool wear by up to 30 %.
    
 
                                                                         
                                                         
                                                         
                                                         
                                                                                                                                                                                                                             
                                                         
                                                         
                                                         
                                                         
                                                         
                                                         
                                                        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