Drilling Techniques and Tools Overview

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Questions and Answers

Which of the following is a primary factor that a single point tool improves when boring?

Speed of operation

Material type

Location of the hole (correct)

Weight of the workpiece

What type of machine performs jig boring operations?

Milling machines

Lathe machines

Horizontal boring machines

Vertical boring machines (correct)

What is the typical diameter range for holes that can be bored?

1/4 inch and larger (correct)

Exactly 1/4 inch

Smaller than 1/4 inch

More than 2 inches

When the boring operation is carried out on a lathe, what is the workpiece doing?

It is rotated Signup and view all the answers

Which of the following best describes a horizontal boring mill?

A large milling machine capable of boring and milling Signup and view all the answers

What is the tolerance level achievable with high-quality boring machines?

One to two ten thousandths of an inch Signup and view all the answers

What is the main purpose of a horizontal boring mill's end support column?

To stabilize long boring bars Signup and view all the answers

Which factor is enhanced by the rigidity of the tool spindle and workpiece holder during boring?

Desired accuracy in the bored hole Signup and view all the answers

What is the primary purpose of counterboring?

To produce a recess of prescribed depth Signup and view all the answers

Which machining operation is typically performed to provide a smooth and perpendicular flat surface for a fastener?

Spotfacing Signup and view all the answers

What operation involves adding a chamfer at the entry end of a hole?

Countersinking Signup and view all the answers

What is the primary function of a reamer in machining?

To provide a more accurate diameter Signup and view all the answers

Which of the following statements about reaming is true?

The operation can be performed by hand Signup and view all the answers

Boring is primarily used for which purpose in machining?

To enlarge and improve the accuracy of an existing hole Signup and view all the answers

How much material do reamers typically remove from a hole's diameter?

$0.005$ to $0.015$ in Signup and view all the answers

What allows a reamer to follow the direction of an existing hole?

Its floating design Signup and view all the answers

What is the primary purpose of drilling?

To create holes in the workpiece Signup and view all the answers

What type of tool is most commonly used for drilling?

A twist drill Signup and view all the answers

Which of the following describes the motion of the drill and workpiece during drilling?

The drill is fed axially into the workpiece Signup and view all the answers

What is a key feature of vertical boring mills?

They have a horizontal table rotating on a vertical axis. Signup and view all the answers

What is counterboring primarily used for?

To enlarge a hole for a part of its depth Signup and view all the answers

What characterizes the workpieces typically machined on a vertical boring mill?

They are round and heavy with large diameters. Signup and view all the answers

How does a counterboring tool maintain alignment with the existing hole?

It is guided by a pilot that fits into the existing hole Signup and view all the answers

What is the main purpose of a gun drill?

To manufacture gun barrels and achieve deep, straight holes. Signup and view all the answers

What happens to the chips produced during the drilling process?

They are carried away by the flutes in the drill Signup and view all the answers

How does a gun drill prevent overheating during operation?

Through the flow of oil coolant at high pressure. Signup and view all the answers

What is a distinguishing feature of the twist drill?

The body is engineered to effectively remove chips. Signup and view all the answers

What characteristic does a twist drill have?

Two or more cutting edges at the end Signup and view all the answers

Which type of drilling machine is the most common?

Drill press. Signup and view all the answers

What does the shank of a twist drill do?

Holds the drill in the drill spindle. Signup and view all the answers

Which operation can vertical boring mills perform?

Boring and facing of large workpieces. Signup and view all the answers

Study Notes

Drilling Definition

Drilling is a cutting process used primarily to make round holes, typically with a twist drill.
The twist drill has helical flutes and two or more cutting edges.
The workpiece or the cutting tool can rotate during drilling.

Drilling Methods

Drilling on a drilling machine involves the tool feeding and cutting action.
Drilling on a turning or automatic lathe involves the workpiece performing the cutting actions.

Twist Drills

Common drilling tool, a rod with helical flutes and cutting edges.
Rotated around its axis and fed into the work.
Carries away chips through the flutes.
Can have various numbers of cutting edges.

Drilling Operations

Drilling - creates or enlarges a round hole.
Core drilling - Creates a hole with a hollow center.
Step drilling - Creates a step-like hole change in diameter.
Counterboring - Creates a larger, deeper hole for a fastener head. (usually flat bottom)
Countersinking - Creates chamfer at the entry of a hole for tapered objects like screws.
Reaming - Improves surface finish, accuracy, and straightness of existing holes.
Center drilling - Prepares a center point for drilling.
Gun drilling - Creates straight deep holes, typically, using oil or coolant.
Jobber's Drill - High-pressure coolant is used.

Drilling Machines

Used for drilling, tapping, and reaming.
Typical types are drill presses, vertical drilling machines.
Variety of sizes.
Usually have a table for holding the workpiece.
Adjustable spindles to accommodate different drill sizes.

Boring

Used to enlarge and improve the accuracy of an existing hole.
Either the work or the drill rotates.
Increases hole accuracy, diameter, cylindricity, and finish.
Commonly used for larger holes difficult or inaccurate to drill.
Can be performed on boring machines or lathes.

Jig Boring

Very high precision vertical boring machines.
Used for making jigs, molds, patterns
Usually used when very accurate hole location is needed

Horizontal Boring Mills

Basically large horizontal milling machines.
Used to machine large complex parts.
Table capable of movement in x and y directions and some swivel in z direction.
Typically used in the machining of large parts with horizontal holes.

Vertical Boring Machines

Machines with a horizontal table rotating on a vertical axis.
Precision tool head for up/down & side-to-side movements.
Used for boring and other operations on larger parts

Gun Drilling

Rotating single-flute (carbide tipped) drill for creating long straight deep holes
Guided using a bushing with coolant/bearing support
Deep straight holes can be made with this method

Drilling Tools (Twist Drills)

Consists of a body, drill point, and shank
Point types (chisel, crankshaft)
Features like shank diameter, length, flute length, and helix angle, margin and lip relief influence the cutting action.

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Description

This quiz covers the essential concepts of drilling, including definitions, methods, and the types of tools used in the process. Test your knowledge about twist drills, drilling operations, and the nuances of various drilling techniques. Perfect for anyone looking to enhance their understanding of this fundamental machining process.