Historical Development of Metalworking
– Oldest evidence of copper mining and working in northern Iraq from 8,700 BCE
– Earliest metalworking in the Americas with copper processing in Wisconsin around 4000-5000 BCE
– Oldest gold artifacts from the Bulgarian Varna Necropolis dating back to 4450 BCE
– Gold speculated to be the first metal due to its natural occurrence as nuggets
– Metalworking carried out in Mehrgarh (South Asia) between 7000 and 3300 BCE
– Bronze production became common around 2700 BCE
– Iron began to be smelted and emerged as an important metal
– Iron Age followed the period of bronze production
– Precious metals gained value during historical periods (Pharaohs in Egypt, Vedic Kings in India, etc.)
– Metalworkers skilled at creating adornments, religious artifacts, and trade instruments
– Extraction of metal ores and metalworking skills evolved over time
– Metalworkers played important roles in society, affecting economies and civilizations

Metalworking Processes
– Use of tools like combination squares and calipers for precise measurements
– Various ancient techniques, such as granulation, still used by metalsmiths today
Metal objects became more common and complex over time
– Importance of acquiring and working metals grew
– Metals are crucial for jewelry, electronics, construction, and transportation industries
– Forming modifies metal or workpiece without removing any material
– Plastic deformation involves using heat or pressure
– Bulk forming processes include forging, extrusion, and rolling
– Sheet forming processes involve mechanical force at room temperature
– Powder metallurgy is a bulk forming process
– Cutting removes excess material using various tooling
– Chip producing processes include machining and drilling
– Burning processes cut metal by oxidizing a kerf
– Specialty processes include chemical milling
– Technologies for cutting metal include sawing, milling, and plasma cutting
– Milling is the shaping of metal by removing material
– It is done on a milling machine with a rotating cutter
– CNC milling machines can perform complex operations
– Tolerances vary depending on the machine and country
– Coolant is used to keep the bit and material cool
– Turning is a metal cutting process for producing cylindrical surfaces
– It is done on a lathe with a single point tool
– The workpiece is rotated on a spindle
– Surfaces perpendicular to the workpiece can be produced
– Turning is commonly used for cylindrical parts
– Safety is key when working with metalworking machines
– High-speed bits and scalding hot metal pose risks
– CNC milling machines provide operator protection
– Proper coolant usage helps maintain safety
– Training and adherence to safety protocols are essential

Lathe Operations
– Chamfering: Cutting an angle on the corner of a cylinder
– Parting: Cutting off the end of a part by feeding the tool radially
– Threading: Creating external or internal threads using a tool fed along the surface
– Boring: Creating a round hole by feeding the tool linearly
– Drilling: Feeding the drill into the workpiece axially
– CNC lathes can perform secondary operations like milling
– They use x, y, and z coordinates to control the turning tools
– Most modern CNC lathes can produce turned objects in 3D
– They require specialized cutting tools for harder workpieces
– Different types of metal can be turned on CNC lathes
– Threading processes include cutting with taps, dies, and mills
– Taps cut female threads on pre-drilled holes
– Dies cut male threads on cylindrical rods
– Thread milling is another method of creating threads
– Cold root rolling and forming, and thread grinding are other threading processes

Joining and Fixing Techniques
– Soldering: Joining process below 450°C (842°F)
– Similar to brazing, but at lower temperature
– Minimal metallurgical reaction between filler and workpiece
– Weaker joint compared to brazing
– Used in electronics, plumbing, and jewelry making
– Riveting: Ancient metalwork joining process
– Declined in use in the second half of the 20th century
– Retains important uses in industry, construction, and crafts
– Two-headed and unthreaded bolt used to join metal pieces
– Rivets can be removed by shearing off one head and driving it out
– Mechanical fixings: Includes screws and bolts
– Used in flat-pack furniture and joining metal to other materials
– Can be used with an intermediate material like nylon
– Weaker than welding or brazing, but metal can be easily removed and reused
– Can be used in conjunction with epoxy or glue

Additional Metalworking Processes
– Heat treatment alters metal properties like strength and hardness
– Common heat treatment processes include annealing, quenching, and tempering
– Thermo-mechanical treatments combine mechanical and thermal treatments
– Plating and thermal spraying are surface-treatment techniques
– Electroplating is a common surface-treatment technique
– Thin layer of another metal bonded to the surface of the product
– Reduces corrosion and improves abrasion resistance
– Can change properties like conductivity and heat dissipation
– Four main electroplating methods: mass plating, rack plating, continuous plating, and line platingSources: