Drilling operation Combine operation Complex process

Countersinking ,boring, counterboring,reaming,tapping

COUNTERSINKING OPERATION

• tapering or bevelling of the end of a hole• conical cutter• form recesses for flathead screws• speed approximately one-half of the speed

for the same size drill.• Feed should be light, but not too light to

cause chatter.

COUNTERBORING

• enlarge the upper end of a hole• recess socket head cap screws• standard counter bore cutters.• 0.002 to 0.005 inch per revolution,

TAPPING OPERATION

• cutting a thread in a drilled hole• The tap drill size FROM TABLE.• Two method of tapping• Hand method for large holes• Gear method for small holes

REAMING OPERATION

• Sharp edges• the holes are first drilled • slightly undersized• hand reamer or using a machine reamer • slight chamfer• High accuracy finishing

HAND REAMERS

• used when a greater accuracy in hole size is required

• taper which extends 3/8- to 1/2- inch above Chamfer

• metal to be removed by the reamer, from 0.001- to 0.003-inch

• Never used for power

MACHINE REAMER

• taper shanks to fit the machine spindle.• good clean holes.• Available in1/64 inch for reamers l/2-inch to 1

inch in diameter.• Smooth reaming.• Coolant is used.

Boring operation

• Enlarge the given drill hole