Overview:
This 1919 book, “Turning and Boring,” serves as a comprehensive guide for machinists, students, and apprentices on the practical aspects of turning and boring. It focuses less on the design and construction of machine tools and more on the techniques and principles of using them effectively. The book delves into various turning and boring operations, including cylindrical and taper turning, thread cutting, and the use of different machine tools like engine lathes, turret lathes, vertical boring mills, and horizontal boring machines.
The text discusses essential elements of machine tool operation, such as tool grinding, cutting speeds, and feeds. It provides detailed explanations of specialized techniques like taper turning using various methods, including the offset-center method, the taper attachment, and the compound rest. Additionally, it explores thread cutting in detail, covering different thread forms, change gear calculations, and the use of thread indicators. The book further examines various types of tools and attachments commonly used in turning and boring, including box-tools, hollow mills, self-opening dies, collapsing taps, and more.
Key Findings:
- The importance of tool grinding and its impact on cutting efficiency and tool durability.
- The principles behind cutting speed and feed selection, considering factors like material hardness, tool quality, and desired finish.
- Different methods for turning tapers, including setting the tailstock center, utilizing taper attachments, and using the compound rest.
- The use of change gears in thread cutting and how to calculate them for various thread pitches and multiple threads.
- The advantages and disadvantages of different turning and boring machines, highlighting their specific applications for various tasks.
Learning:
- Tool Grinding: This text emphasizes the importance of proper tool grinding for achieving optimal cutting performance. Readers will learn about the key elements of tool grinding, including the shape of the cutting edge, clearance angle, and the direction of the top slope. Understanding the principles behind these elements allows readers to grind tools effectively for different materials and operations.
- Cutting Speeds and Feeds: The book thoroughly explains the factors that influence cutting speed and feed selection in lathe turning. Readers will learn how to determine the ideal cutting speed for various materials based on the hardness, tool type, and depth of cut. They will also understand how feed rate affects the time taken to remove metal and the surface finish produced.
- Taper Turning: The text offers detailed explanations and instructions on several methods for turning tapers. Readers will learn how to set the tailstock center for a desired taper, understand the operation of taper attachments, and use the compound rest to create steeper tapers.
- Thread Cutting: This text provides a comprehensive guide to thread cutting, including the different thread forms commonly used, how to select the appropriate change gears, and the use of thread indicators for precise thread cutting. The book also covers the process of cutting multiple threads and tapers threads.
- Machine Tool Selection: The book highlights the advantages and disadvantages of different turning and boring machines, providing a better understanding of when to select each type for specific tasks. Readers will learn about the unique features of engine lathes, turret lathes, vertical boring mills, and automatic chucking and turning machines, enabling them to make informed decisions about which machine best suits their needs.
Historical Context:
The book was written in 1919, just after World War I, a time of significant technological advancement and rapid industrialization. The text reflects the state of manufacturing technology during that period, emphasizing the importance of efficiency and productivity.
Facts:
- Tool Shape: The shape of the cutting edge depends on the intended purpose. Roughing tools have a large radius for faster cutting, while finishing tools have smaller points for a smoother finish.
- Tool Clearance: A clearance angle of 8-10 degrees is generally ideal for lathe turning tools to prevent the flank from rubbing against the work.
- Tool Slope: The direction of the top slope of a turning tool should be away from the working part of the cutting edge to reduce cutting force.
- Cutting Speed and Hardness: Harder metals require slower cutting speeds than softer metals.
- Cooling Lubricants: Using cooling lubricants like soda water can increase cutting speed by up to 40% for high-speed steel tools.
- Lard Oil: Lard oil is a good lubricant for turning steel and wrought iron.
- Taper per Foot: Taper is often expressed in inches per foot, representing the difference in diameter over a length of 12 inches.
- Offset Center Method: Taper turning can be achieved by offsetting the tailstock center from the headstock center.
- Taper Attachment: A taper attachment allows precise taper turning without offsetting the tailstock center.
- Compound Rest: The compound rest is used for turning steep tapers or angles.
- Thread Forms: Common thread forms include V-thread, U.S. Standard, and square thread.
- Multiple Threads: Multiple threads (double, triple, etc.) provide a greater lead without weakening the screw.
- Left-hand Thread: A left-hand thread winds in the opposite direction to a right-hand thread.
- Thread Indicators: Thread indicators help “catch” threads by ensuring the carriage engages with the lead-screw at the correct position for each cut.
- Root Diameter: The root diameter of a thread is the diameter at the bottom of the grooves.
- Three-wire System: The three-wire system uses wires and a micrometer to measure the pitch diameter of a thread.
- Forced Fit: A forced fit is achieved by pressing a pin or shaft into a hole with a press, requiring a slight allowance for the fit.
- Shrinkage Fit: A shrinkage fit is achieved by heating the outer member and then cooling it after inserting the inner member, resulting in a tight fit.
- Turret Lathes: Turret lathes are designed for high-volume production of duplicate parts, using tools held in a revolving turret.
- Automatic Chucking and Turning Machines: These machines automate the turning and boring process, using cams and dogs to control tool movements and speed changes.
Statistics:
- Cutting Speed for Ordinary Machine Steel: 45-65 feet per minute.
- Cutting Speed for Ordinary Cast Iron: 40-50 feet per minute.
- Cutting Speed for Annealed Tool Steel: 25-35 feet per minute.
- Cutting Speed for Soft Yellow Brass: 150-200 feet per minute.
- Cutting Speed for Hard Bronze: 35-80 feet per minute.
- Taper Allowance per Foot: Ranges from 0.5 to 2.0 inches per foot.
- Typical Forced Fit Allowance per Inch: 0.001-0.0025 inches.
- Typical Shrinkage Fit Allowance per Inch: Smaller than forced fit allowance, but varies depending on the part’s size and shape.
- Time to Machine a Flywheel in a Turret Lathe: 7.5 minutes.
- Number of Tools on a Double-spindle Flat Turret Lathe: 8.
- Number of Spindles on a New Britain Automatic Chucking Machine: 5 (single-head), 8 (double-head).
- Number of Castings Machined in 9 Hours on an Eight-spindle Double-head Machine: 300.
Terms:
- Back-gears: Gears in the headstock of a lathe used to reduce the spindle speed for slower turning operations.
- Compound Rest: An upper slide mounted on the main cross-slide of a lathe, allowing the tool to be fed at an angle.
- Eccentric Turning: Turning one cylindrical surface eccentric to another.
- Form Tool: A tool with a specifically shaped cutting edge for turning a particular profile or shape.
- Follow-rest: A support attached to the lathe carriage for supporting flexible work during turning operations.
- Lead-screw: The screw that moves the carriage in a lathe, used for thread cutting.
- Steadyrest: A support attached to the lathe bed for supporting long, flexible work during turning operations.
- Taper Attachment: A device on a lathe that allows precise taper turning without offsetting the tailstock center.
- Thread Gage: A tool used for setting and testing the angle of thread tools.
- Worm Thread: A thread with a steep lead, often used in gear drives.
Examples:
- Turning a Steel Shaft: The book describes the process of turning a steel shaft to a specific diameter and length between lathe centers, demonstrating the use of turning tools, calipers, and hand feeds.
- Facing the Ends of a Shaft: The text explains the use of a side-tool for facing the ends of shafts square with the axis.
- Turning a Pulley on an Arbor: The book discusses turning a pulley held on a lathe arbor, highlighting the importance of mandrels for turning parts with holes.
- Boring a Hole in a Pulley: The text describes the process of boring a hole through a pulley held in a chuck, explaining the use of boring tools and methods for measuring the hole diameter.
- Centering Parts for Turning: The book details different methods of forming center-holes in workpieces, including the use of center-punches, drills, and specialized centering machines.
- Turning Taper Plugs: The text demonstrates the process of turning a taper plug to fit a ring gage, using the offset-center method and caliper tools for precise measurement.
- Turning a Steering Knuckle: The book uses the example of turning a steering knuckle on a Lo-swing lathe to illustrate the capabilities of multi-tool turning.
- Turning a Crankshaft: The book describes the process of turning an engine crankshaft, highlighting the use of special lathes and attachments for this operation.
- Turning Spherical Surfaces: The text discusses how spherical surfaces are turned using the compound rest and dedicated spherical turning attachments.
- Cutting a U.S. Standard Thread: The book provides a detailed explanation of cutting a U.S. Standard thread, including the use of thread tools, gages, and the three-wire system for measuring the pitch diameter.
Conclusion:
“Turning and Boring” offers a valuable resource for understanding the principles and techniques of turning and boring operations. The book covers a wide range of topics, including tool grinding, cutting speeds and feeds, taper turning, thread cutting, and the operation of different types of machine tools. It provides detailed explanations and practical examples, making it a helpful guide for machinists, students, and apprentices seeking to improve their skills and knowledge in this area. By carefully studying the text, readers can acquire a solid foundation in turning and boring techniques, enabling them to efficiently and accurately produce a wide variety of components used in various industries.