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Material Selection: Choosing What to Cut

Selecting the right material is fundamental to successful lathe work. This guide covers common materials, their properties, and practical considerations for beginners setting up their first workshop.

Understanding Machinability

Machinability refers to how easily a material can be cut, shaped, and finished on machine tools. Materials with good machinability:

  • Form chips that break easily rather than creating long strings
  • Require less cutting force and power
  • Produce better surface finishes
  • Cause less tool wear
  • Are more forgiving of speed and feed variations

Free-machining grades contain additives (like lead or sulfur) that improve chip formation and reduce cutting forces. These materials are ideal for beginners learning proper techniques.

Steel Types and Selection

Steel comes in countless grades, but beginners need focus on just a few key types. Understanding the basics helps avoid costly mistakes and frustration.

Cold Rolled vs Hot Rolled

Cold Rolled Steel

  • Smooth, clean surface finish
  • More precise dimensions
  • Better for machining operations
  • Slightly more expensive
  • Recommended for lathe work

Hot Rolled Steel

  • Characteristic orange-peel "mill scale" surface
  • Less precise dimensions
  • Better for welding and fabrication
  • Requires scale removal before precision work
  • Generally avoid for beginner projects

Essential Steel Grades

1018 Mild Steel

  • General purpose, low carbon steel
  • Inexpensive and widely available
  • Can be welded easily
  • Requires more skill to achieve good finishes
  • Good for projects needing both machining and welding

12L14 Free-Machining Steel

  • Contains small amount of lead for machinability
  • Excellent for learning and practice
  • Produces superior surface finishes easily
  • Very forgiving of speed/feed errors
  • Cannot be welded effectively
  • Ideal first steel for beginners

Mystery Steel Warning

"Mystery steel" refers to any material of unknown composition - salvaged parts, unmarked bar stock from estate sales, or that piece of round bar that's been in the corner for years. While it's tempting to use free or cheap material, especially when starting out, mystery steel creates more problems than it solves. The alloy content, heat treatment, and even basic carbon content remain unknown, making it impossible to work with predictably.

Without knowing the grade, you face several serious challenges:

  • Proper speeds and feeds cannot be determined
  • Results will be inconsistent
  • Learning becomes unnecessarily difficult
  • Safety risks increase with unknown materials

Always purchase known grades. Label and store your stock clearly.

Aluminum Alloys for Beginners

Aluminum offers lightweight, corrosion-resistant options that machine well.
For hobby work, one alloy dominates.

6061 Aluminum

  • Standard general-purpose aluminum
  • Excellent strength-to-weight ratio
  • Machines beautifully in milling operations
  • Creates long, stringy chips on the lathe
  • Requires sharp tools and proper speeds
  • Very affordable and available everywhere

The main challenge with aluminum on the lathe is chip control. Even experienced machinists struggle with the long strings it produces. Use chip breakers and frequent clearing to manage this issue.

Brass and Bronze Options

Brass machines exceptionally well and offers unique advantages for specific applications. Focus on these common alloys.

Brass Fundamentals

360 Free-Machining Brass

  • Also known as C36000
  • Excellent machinability
  • Simple tool geometry requirements
  • More expensive than steel or aluminum
  • Available in convenient shapes (hex bar for fittings)
  • Ideal for decorative and precision parts

Brass costs more but rewards beginners with easier cutting, better finishes, and more forgiving behavior. The investment pays off in learning speed.

Bronze Applications

932 Bearing Bronze

  • Specialized material for bearings and bushings
  • Expensive but necessary for certain applications
  • Recognizable purple-striped appearance
  • Excellent for steam engine work
  • Resists dezincification unlike brass
  • Often available as hollow bar to reduce cost

Cost-saving tip: Check plumbing fittings for bronze stock. Cast fittings often provide cheaper bronze than bar stock, though casting quality varies.

Specialty Materials

Some projects require materials beyond the basics. Here are key options to know about, though beginners should master standard materials first.

Tool Steel

  • Hardenable for making cutting tools
  • Available as precision-ground drill rod
  • More expensive and harder to source
  • Challenging to machine on light equipment
  • O1 and W1 common grades for beginners

Stainless Steel

  • 303 or 316 grades easiest to machine
  • Requires rigid setup and proper technique
  • Work hardens quickly if speeds too slow
  • Special cutting fluids recommended

Engineering Plastics

Delrin (Acetal)

  • Machines beautifully with standard tools
  • Creates long chips like aluminum
  • Excellent for oil-free bearings
  • Quiet operation in moving parts
  • No cutting fluid needed

Reading Material Designations

Understanding material naming helps when ordering:

  • Steel: Four digits (1018, 1215, 4140)
  • Aluminum: Four digits (6061, 7075)
  • Brass: Three digits + zeros (360, 260)
  • Bronze: Three digits (932, 954)

Letters indicate special properties:

  • L = Lead added (12L14)
  • T = Temper designation (6061-T6)

Sourcing and Cost Considerations

Finding affordable materials requires exploring multiple sources:

Local Suppliers

Advantages:

  • Immediate availability
  • Can inspect material
  • Expert advice available
  • Often deliver
  • May cut to length

Disadvantages:

  • High minimum orders (10-20 feet)
  • Limited hobby-friendly materials
  • Can be intimidating for beginners

Pro tip: Check the off-cuts bin first. Random short pieces sell cheap and provide variety for learning.

Online Options

eBay

  • Perfect for small quantities
  • USPS flat-rate boxes keep shipping reasonable
  • Wide variety of sizes and materials
  • Search for specific sellers specializing in hobby quantities

Online Metals / Metal Supermarkets

  • Broader selection than eBay
  • Cut to custom lengths
  • Higher prices but reliable quality
  • Good for exotic materials

McMaster-Carr

  • Excellent for unusual materials
  • Short lengths available
  • Fast shipping
  • Premium prices

Budget Strategies

  1. Buy only what you need for current projects
  2. Start with affordable materials (1018, 6061)
  3. Check local scrap yards for practice material
  4. Split larger orders with other hobbyists
  5. Save and organize all usable scraps

For your first material order, consider:

  1. 12L14 steel round bar - ½" and ¾" diameter
  2. 6061 aluminum round bar - ½" and 1" diameter
  3. 360 brass round bar - ½" diameter
  4. Delrin rod - ½" diameter

These sizes handle most beginner projects while providing variety for learning different cutting characteristics.

Storage and Organization

Proper material storage prevents confusion and waste:

  • Label everything with grade and size
  • Store vertically when possible
  • Protect from moisture (especially steel)
  • Keep materials sorted by type
  • Maintain a simple inventory list

Safety Considerations

  • Never machine materials producing toxic fumes or dust
  • Avoid beryllium copper and leaded materials without proper ventilation
  • Research any unknown materials before cutting
  • Some plastics release dangerous gases when heated