DRILLING Diagram shows the parts of a standard pillar drilling machine.

DRILLING The drill speed can be altered by changing the position of the vee belt on the stepped pulleys. Most modern drilling machines now have gear boxes which enable their speed to be changed by moving gear levers.

DRILLING A chuck guard is fitted to the drilling machine and the machine should never be used without it.

METHODS OF HOLDING WORK

DRILLING The hand drill is driven by hand and is suitable only for light drilling.

DRILLING Battery operated hand drill. This is powered by a rechargable battery.

Drilling

DRILLING

DRILLING Morse taper sleeves are used when the taper shank of a tool is too small for the machine socket.

DRILLING

DRILLING Locate the position of the hole centre by means of intersecting lines and centre-punch the intersection. A pilot hole must be drilled before using a large drill e.g. 8 or 10mm

DRILLING A clearance hole is slightly larger than the the bolt, stud or screw that is passes through it. A blind hole is hole that is not drilled all the way through a part.

DRILLING A tapping size hole is drilled prior to cutting an internal thread. It must be smaller than the tap to allow depth of thread. E.g. for an M6 tap drill a 5mm hole.

DRILLING Countersinking is enlarging the mouths of holes to accommodate the heads of countersunk head screws and rivets.

DRILLING Counterboring is increasing the hole diameters to certain depths, usually to accommodate the heads of screws, such as allen screws and cheese head screws.

DRILLING Spot facing is the machining of the rough surfaces surrounding holes, e.g. holes in castings.

DRILLING Reamers are used for finishing holes smoothly and accurately. A slightly undersize hole is drilled and the reamer is then used to finish it to size.