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
Two ways of cutting: rotate drill or rotate workpiece
Because of confined cutting, coolant is important
- Lubrication
- Cooling
- Chip removal
Drilling Tool Selection
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
- Shank
- Helix Angle
- Flute
- Margin
- Point Angle
- Land
- Chisel Edge
- Web or Core Thickness
- Lip
- Rake Angle
Twist Drill Sizes
- Fractional
- Number
- Letter
- Metric
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
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.
