1. Drilling Machines
Section 10

2. Drilling Machines Probably first mechanical device developed
Principle of rotating tool to make hole
One of most common and useful machines in industry
Come in several types and sizes
From hand-fed to computer-controlled

3. Drill Presses
Unit 38

4. Objectives
Identify six standard operations that may be performed on a drill press
Identify four types of drill presses and their purposes
Name and state the purpose of the main parts of an upright and a radial drill

5. Drilling Press Drilling machine Spindle Work table
Turns drill to advance into work (hand or automatically)
Work table
Holds workpiece rigidly in place as hole drilled
Used primarily to produce holes in metal
Other operations: tapping, reaming, boring, counterboring, countersinking, spot-facing

6. Standard Operations Drilling Countersinking
Operation of producing hole by removing metal from solid mass using twist drill
Countersinking
Operation of producing tapered or cone-shaped enlargement to end of hole
> Countersinking (Fig. 38-1b) is the operation of producing a tapered or cone-shaped enlargement to the end of a hole.
> Reaming (Fig. 38-1c) is the operation of sizing and producing a smooth, round hole from a previously drilled or bored hole with the use of a cutting tool having several cutting edges.
> Boring (Fig. 38-1d) is the operation of truing and enlarging a hole by means of a single-point cutting tool, which is usually held in a boring bar.
> Spot-facing (Fig. 38-1e) is the operation of smoothing and squaring the surface around a hole to provide a seat for the head of a cap screw or a nut. A boring bar, with a pilot section on the end to fit into the existing hole, is generally fitted with a double-edged cutting tool. The pilot on the bar provides rigidity for the cutting tool and keeps it concentric with the hole. For the spot-facing operation, the work being machined should be securely clamped and the machine set to approximately one-quarter of the drilling speed.
> Tapping (Fig. 38-1f) is the operation of cutting internal threads in a hole with a cutting tool called a tap. Special machine or gun taps are used with a tapping attachment when this operation is performed by power in a machine.
> Counterboring (Fig. 38-1g) is the operation of enlarging the top of a previously drilled hole to a given depth to provide a square shoulder for the head of a bolt or capscrew.
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7. Standard Operations Reaming Boring
Operation of sizing and producing smooth, round hole from previously drilled or bored hole
Boring
Truing and enlarging hole by means of single-point cutting tool
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8. Standard Operations Tapping Counterboring
Cutting internal threads in hole with cutting tool called tap
Counterboring
Enlarging top of previously drilled hole to given depth to provide square shoulder for head of bolt or capscrew
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9. Standard Operations
Smoothing and squaring surface around hole to provide seat for head of cap screw or nut
Boring bar fitted with double-edged cutting tool
Pilot section on end to fit into existing hole
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10. Principal Types of Drilling Machines
Wide variety of drill presses
Size of drill press may be designated in different ways by different companies
Some state size as distance from center of spindle to column of machine
Others state size by diameter of largest circular piece that can be drilled in center

11. Sensitive Drill Press Parts
Only hand feed mechanism
Control downfeed pressure
Manufactured in bench and floor model
Four main parts
Base, column, table and drilling head
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12. Sensitive Drill Press Parts
Base
Provides stability for machine
Cast iron with holes to be bolted to table or bench
Slots or ribs in base allow work-holding device or workpiece to be fastened
Column
Accurate cylindrical post that fits in base
Table may be adjusted any point (base to head)
Drill press head mounted near top
Table
The table, either round or rectangular in shape, is used to support the workpiece to be machined. The table, whose surface is at 90° to the column, may be raised, lowered, and swiveled around the column. On some models, it is possible to tilt the table in either direction for drilling holes on an angle. Slots are provided in most tables to allow jigs, fixtures, or large workpieces to be clamped directly to the table.
Drilling Head
The head, mounted close to the top of the column, contains the mechanism used to revolve the cutting tool and advance it into the workpiece. The spindle, which is a round shaft that holds and drives the cutting tool, is housed in the spindle sleeve, or quill. The spindle sleeve does not revolve but slides up and down inside the head to provide a downfeed for the cutting tool. The end of the spindle may have a tapered hole to hold taper shank tools or may be threaded or tapered for attaching a drill chuck (Fig. 38-2).

13. Sensitive Drill Press Parts
Table
Round or rectangle
Used to support workpiece to be machined
Surface 90º to column (move around)
Drilling Head
Mechanism used to revolve cutting tool
Spindle: round shaft holds cutting tool
Quill: houses spindle

14. Upright Drilling Machine
Larger and heavier
Differences from sensitive-type drill
Equipped with gearbox for variety of speeds
Spindle may be advanced by: hand lever, handwheel, and automatically by feed mechanism
Table raised or lowered by mechanism
Some have reservoir in base for coolant storage
Multispindle head can be used (20+ spindles)

15. Radial Drilling Machine
Sometimes called radial-arm drill
Advantages of this machine
Larger and heavier work may be machined
Drilling head raised or lowered
Drilling head moves rapidly to any desired location while workpiece remains clamped
More power
Head may swivel so holes can be drilled on angle

16. Radial Drilling Machine
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17. Radial Drilling Machine Parts
Base
Heavy, box-type, ribbed cast iron or welded steel
Used to bolt machine to floor and provide coolant reservoir
Table may be bolted to base for small work
Column
Upright cylindrical member fitter to base
Supports radial arm at right angles
Radial Arm
The arm is attached to the column and may be raised and lowered by means of a power-driven elevating screw. The arm may also be swung about the column and may be clamped in any desired position. It also supports the drive motor and drilling head.
Drilling Head
The drilling head is mounted on the arm and may be moved along the length of the arm by means of a traverse handwheel. The head may be clamped at any position along the arm. The head houses the change gears and controls for the spindle speeds and feeds. The drill spindle may be raised or lowered manually by means of the spindle-feed handles. When the spindle-feed handles are brought together, automatic feed is provided to the drill spindle.

18. Radial Drilling Machine Parts
Radial arm
Attached to column
May be raised and lowered by means of power-driven elevating screw
Supports drive motor and drilling head
Drilling head
Mounted on arm and moved along length of arm by traverse handwheel
Drill spindle may be raised or lowered