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.
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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.
It is a slow process than reaming and requires several passes of the toll. Counterboring Counterboring is the operation of enlarging the end of a hole cylindrically.
The enlarged hole forms a square shoulder with the original hole. This is necessary in some cases to accommodate the heads of bolts, studs and pins.
A tool used for counterboring is called a counterbore. The counterbores are made with a straight or tapered shank to fit in the drill spindle. The cutting edges may have straight or spiral teeth.
The tool is guided by a pilot which extends beyond the end of the cutting edges. The pilot fits into the small diameter hole running clearance and maintains the alignment of the tool.
These pilots may be interchanged for enlarging different sizes of holes. Countersinking Countersinking is the operation of making a cone-shaped enlargement of the end of a hole to provide a recess for a flat head screw or countersunk rivet fitted into the hole. The tool used for countersinking is called a countersink. Standard countersinks have 60, 82 or 90 inclined angle and the cutting edges of the tool are formed at the conical surface.
Spot facing Spot facing is the operation of smoothing and squaring the surface around a hole for the seat for a nut or the head of a screw.
A counterbore or a special spot facing tool may be employed for this purpose.
Tapping It is the operation of cutting internal threads by means of a cutting tool called a tap. Tapping in a drilling machine may be performed by hand or by machine. A tap may be considered as a bolt with accurate threads cut on it.
The threads act as cutting edges which are hardened and ground.
When the tap is screwed into the hole it removes metal and cuts internal threads which will fit into external threads of the same size. Lapping Lapping is the operation of sizing and finishing a small diameter hole already hardened by removing a very small amount of material by using a lap. 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.
Principle and Working of DRILLING MACHINE
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.
Principle and Working of DRILLING MACHINE
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.
Drilling in wood[ edit ] Wood being softer than most metals, drilling in wood is considerably easier and faster than drilling in metal. Cutting fluids are not used or needed. Portable drilling machine: It is a small light weight, compact and self contained unit that can drill holes upto The machine is driven by a small electric motor operating at high speed.
The machine is capable of drilling holes in the workpieces in any position. This is a light weight, high speed machine designed for drilling small holes in light jobs. Generally the machine has the capacity to rotate drills of 1. The machine has only a hand feed mechanism for feeding the tool into the workpiece. This enables the operator to feel how the drill is cutting and accordingly he can control the down feed pressure.
Sensitive drill presses are manufactured in bench or floor models, i.
The base is a heavy casting that supports the machine structure; it provides rigid mounting for the column and stability for the machine. The base is usually provided with holes and slots which help to Bolt the base to a table or bench and allow the work-holding device or the workpiece to be fastened to the base. The column is a vertical post that Column holds the worktable and the head containing the driving mechanism.
The column may be of round or box section. 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.Circle interpolating[ edit ] The orbital drilling principle Circle interpolating, also known as orbital drilling, is a process for creating holes using machine cutters.
They Y axis controls the table movement machine which will make use of computerized numerically towards or away from the column. Tapping in a drilling machine may be performed by hand or by machine. Poduraev, Moscow Bauman University.
Used to correct out of roundness of the hole.
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