PURPOSE. This chapter contains basic information pertaining to drilling machines. A drilling machine comes in many shapes and sizes, from small hand- held. Describe safety, types, components and applications of drilling machines. Safety First. You are using a rotating cutting tool and injury can happen easily. Follow. User Instruction for Bowling Ball Drilling Machine. - 2 -. Thank you for using VIA Bowling Ball drilling machine, which is designed to drill holes on the Bowling.
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1. UNIT 4: Drilling machines: Classification, constructional features, drilling & related operations, types of drill & drill bit nomenclature, drill materials. 6 Hrs. out by a rotating cutting tool to make circular holes in solid materials. Tool which makes hole is called as drill bit or twist drill. Drilling machine is one of the most important machine tools in a workshop. The basic parts of a drilling machine are a base, column, drill head and spindle.
The unit essentially consists of: 1. A spindle which turns the tool called drill which can be advanced in the workpiece either automatically or by hand. A work table which holds the workpiece rigidly in position. Working principle: The rotating edge of the drill exerts a large force on the workpiece and the hole is generated. The removal of metal in a drilling operation is by shearing and extrusion.
The mechanically forced, dynamic offset in orbital drilling has several advantages compared to conventional drilling that drastically increases the hole precision.
The lower thrust force results in a burr-less hole when drilling in metals. When drilling in composite materials the problem with delamination is eliminated. The cutting edges produce more chips which continue the movement of the chips outwards from the hole. This is successful until the chips pack too tightly, either because of deeper than normal holes or insufficient backing off removing the drill slightly or totally from the hole while drilling.
Cutting fluid is sometimes used to ease this problem and to prolong the tool's life by cooling and lubricating the tip and chip flow. Coolant may be introduced via holes through the drill shank, which is common when using a gun drill.
When cutting aluminum in particular, cutting fluid helps ensure a smooth and accurate hole while preventing the metal from grabbing the drill bit in the process of drilling the hole.
When cutting brass, and other soft metals that can grab the drill bit and causes "chatter", a face of approx. This prevents "chatter" during which the drill tears rather than cuts the metal.
However, with that shape of bit cutting edge, the drill is pushing the metal away, rather than grabbing the metal. This creates high friction and very hot swarf.
Magnetic Drilling Machine manufactured by BDS Maschinen GmbH, Germany For heavy feeds and comparatively deep holes oil -hole drills are used in the drill bit, with a lubricant pumped to the drill head through a small hole in the bit and flowing out along the fluting. A conventional drill press arrangement can be used in oil-hole drilling, but it is more commonly seen in automatic drilling machinery in which it is the workpiece that rotates rather than the drill bit. In computer numerical control CNC machine tools a process called peck drilling, or interrupted cut drilling, is used to keep swarf from detrimentally building up when drilling deep holes approximately when the depth of the hole is three times greater than the drill diameter.
Peck drilling involves plunging the drill part way through the workpiece, no more than five times the diameter of the drill, and then retracting it to the surface. This is repeated until the hole is finished. A modified form of this process, called high speed peck drilling or chip breaking, only retracts the drill slightly. This process is faster, but is only used in moderately long holes, otherwise it will overheat the drill bit.
It is also used when drilling stringy material to break the chips. The base allows drilling in a horizontal position and even on a ceiling.
Usually, for these machines, it is better to use cutters because they can drill much faster with less speed.
In the oil and gas industry , pneumatic magnetic drilling machines are used to avoid sparks, as well as special tube magnetic drilling machines that can be fixed on pipes of different sizes, even inside. The table height is adjustable and power speed and feeds are available.
The larger drills normally have taper shank which located within taper bore in the spindle end.
Radial Arm: The radial drill is free standing and the workpiece is clamped in the position on the base. It is used for heavy large and heavy work. The arm is power driven for the height location. The drill head is positioned using motorized drives and it transverse the swinging arm.
The machine spindle is moved to the location required. Multi-spindle: There are many spindles mounted on one head to allow many holes to be drilled simultaneously.
Numerical Control Drilling Machine: The machine can automatically change tooling with a turret or automatic tool changer. Speeds, fee, and table position are controlled using a computer program.
Drilling Machine: Twist drill nomenclature: It is designed with cones like internal structure, narrow at the top or the web with a gradually increasing thickness to the shank. The column may be of round or box section. Table: The table, either rectangular or round. The surface of the table is degree to the column and it can be raised, lowered and swiveled around it.
Slots are provided in most tables to allow the jigs, fixtures or large workpieces to be securely fixed directly to the table. Drilling Head: The drilling head, mounted close to the top of the column, houses the driving arrangement and variable speed pulleys.
These units transmit rotary motion at different speeds to the drill spindle.
The hand feed lever is used to control the vertical movement of the spindle sleeve and the cutting tool.