Drilling and Related Hole-Making Processes

LECTURE PRESENTATION

Reading Assignment

  • 23.1 Introduction to Drilling and Holemaking
  • 23.2 Fundamentals of the Drilling Process
  • 23.3 Types of Drills
  • 23.4 Tool Holders for Drills
  • 23.5 Workholding for Drilling
  • 23.6 Machine Tools for Drilling
  • 23.7 Cutting Fluids for Drilling
  • 23.8 Counterboring, Countersinking and Spot Facing
  • 23.9 Reaming

Recommended Reading

Additional Reading

Outline

Introduction

Drilling is a common process, almost 1/2 of all chips are from drilling
Two ways of cutting: rotate drill or rotate workpiece
Because of confined cutting, coolant is important

  • Lubrication
  • Cooling
  • Chip removal

Drilling Tool Selection

There are many types of drilling tools and methods.
Selection is based on:
  • Hole Diameter
  • Hole Depth
  • Tolerance Required
  • Material Type and Conditions
  • Number of holes needed

Hole Types

  • Through
  • Blind
  • Interrupted

Short Hole Drilling

  • Ratio of depth to diameter
  • Short holes are drilled in one motion
  • Rule of thumb for holes that can be drilled in one motion: 3 or 4 diameters for drills up to one inch. ¬†2.5 diameters for larger holes.

Deep Hole Drilling

  • Peck drilling – Repeated withdrawal of the drill to clear chips from flutes.
  • Rule of thumb: 3X drill diameter per peck.
  • Deep hole drilling is more difficult
    • Hard to keep hole straight
    • May require guides, special drills
    • Through-tool coolant often helpful/required

Twist Drills

A twist drill is a round, end-cutting tool with one or more cutting lips and one or more helical flutes.
Twist Drill Geometry
  • Shank
  • Helix Angle
  • Flute
  • Margin
  • Point Angle
  • Land
  • Chisel Edge
  • Web or Core Thickness
  • Lip
  • Rake Angle

Twist Drill Sizes

  • Fractional
  • Number
  • Letter
  • Metric
ANSI/ASME B94.11M-1993
Twist Drills
This standard covers Nomenclature, Definitions, Sizes and Tolerances of High Speed Steel, Straight and Taper Shank Drills, Combined Drills and Countersinks, Plain Bell Type, In Both Inch and Metric Sizes.

Drill Types

  • Twist Drill
  • Center Drill
  • Spot Drill
  • Piloted Drill
  • Spade Drill
  • Friction Drill
  • Subland Drill
  • Step Drills
  • Multistep Drills
  • Gun Drills
  • Trepanning/Rotabroach Drills

Cutting Parameters

Cutting speed

Measured at the periphery of the drill body and expressed in surface feet per minute

Feed/penetration rate

The distance of travel into the stock per unit of time and expressed as inches or millimeters per minute. The harder the material, the slower the cutting speed and feed rate.

It is easy to burn up a drill bit.

Hole Finishing

Reaming

Boring

Burnishing

Machines for Holemaking

Sensitive Drill Press
Radial Drill
Gang Drilling Machines
Self-Feeding Drilling Units
Multiple-Spindle Drilling MachinesLathes
Mills

Additional Information

Reamers ANSI/ASME B94.2-1995 - This Standard covers the American National Standard for Reamers-nomenclature, definitions, types, sizes, and tolerances.

Twist Drills ANSI/ASME B94.11M-1993 – This standard covers Nomenclature, Definitions, Sizes and Tolerances of High Speed Steel, Straight and Taper Shank Drills, Combined Drills and Countersinks, Plain Bell Type, In Both Inch and Metric Sizes.