Cutting Tools: Types, Geometry, and Selection

Overview of Topics

• Cutting-Tool Types
• Cutting-Tool geometry
• Cutting-tools for different operations
• Turning Operation Times
• Tool selection

Cutting-Tool Types

• There are three main types of cutting tools: integral, welded insert, and interchangeable insert.
• Refer to https://www.youtube.com/watch?v=q5TCwOwGPiE&ab_channel=AutoHub for further visual understanding.

Integral Tools

• The whole tool is made of cutting-tool material, typically high-speed steel (HSS).
• Durable but require resharpening.
• Made from high-speed steel (HSS) or carbide.
• Manufactured from square or round bars by grinding or forging.
• Less common in modern industry, they are useful for:
  • Custom tool profiles in shaping operations.
  • Low-cost machining where tool replacement is infrequent.
  • Precision form cutting in prototyping.
• Right-hand or left-hand tools are based on cutting direction.
• Types of integral tools include:
  • Straight and curved tools for general turning.
  • Cutting-edge tools for high precision.
  • Wide tools for heavy material removal.
  • Side cutting tools for facing and contouring.
  • Form tools for grooving, threading, and special profiles.

Welded Insert Tools

• A steel tool body with a carbide or ceramic insert is welded onto the cutting edge.
• More wear-resistant than integral tools.
• More rigid and stable than interchangeable inserts.
• Lower cost compared to fully carbide tools.
• Cannot be replaced when worn and must be reground or discarded.
• Not ideal for high-speed machining due to heat accumulation.
• Common applications include:
  • Medium-production environments where tool life is a priority and where replacement costs must be minimized.
  • Suitable for custom tool geometries that are not available as interchangeable inserts.
• Standard Geometries:
  • Turning tool (ISO 1, 2 and 6)
  • Tip tool Tool angled to the left.
  • Tool angled to the right (ISO 3)
  • Front cutting tool (ISO 5)
  • Interior tools (ISO 8 and 9)
  • Tools for grooving (ISO 4 and 7).

Interchangeable Insert Tools

• The most widely used cutting tools in modern machining, especially in high-speed and precision turning.
• Inserts are fixed by some method that allows for exchange once worn (not sharpened).
• Inserts are typically made from carbide, cermet, ceramic, or polycrystalline diamond (PCD) for advanced machining applications.
• Offer superior performance, extended tool life, and quick insert replacement.
• Clamping System Types:
  • Flange: Easy to change but less secure at high speeds.
  • Screw: More compact and highly stable, but takes longer to replace.
  • Lever: Allows for quick insert changes, but applies uneven stress, which may cause insert failure in demanding operations.
• Ensure stability and precise positioning by placing the insert on a support plate.

Comparison of Cutting-Tool Types

• Integral Tools:
  • Material: Single piece of HSS or carbide
  • Sharpening: Can be resharpened and reused
  • Durability: Lower due to wear over time
  • Cost: Low initial cost, high long-term cost (regrinding)
  • Performance: Limited; suitable for low-speed operations
  • Tool Change Time: Slow; requires regrinding or replacement
  • Best for: Custom tools, prototyping, and low-cost machining
  • Application: Specialized cases for soft metals or prototypes
• Welded Insert Tools:
  • Material: Steel body with welded carbide/ceramic tip
  • Sharpening: Can be reground but loses shape
  • Durability: Higher than integral, limited lifespan
  • Cost: Medium, needs replacement
  • Performance: Moderate, heat buildup is a concern
  • Tool Change Time: Moderate, replacement after wear
  • Best for: Medium-production machining with specific geometries
  • Application: specific operations requiring custom profiles
• Interchangeable Insert Tools:
  • Material: Steel or carbide tool holder with replaceable carbide, cermet, ceramic, or PCD insert
  • Sharpening: Cannot be sharpened; replaced when worn
  • Durability: Longest multi-edged inserts
  • Cost: Higher initial cost, cost-effective in the long run
  • Performance: Excellent, high-speed cutting
  • Tool Change Time: Fast, quick replacement
  • Best for: High-speed, high-precision, mass production
  • Application: Dominates aerospace machining (titanium, Inconel)

Cutting-Tool Geometry

• The majority of turning operations uses single-point cutting tools, with the geometry of a typical right-hand cutting tool.
• Refer to https://www.youtube.com/watch?v=fCE7absndlc&ab_channel=ADTWStudy for further visual understanding.
• The angles in a single-point cutting tool have important functions in machining performance, affecting cutting forces, chip flow, heat generation, and tool wear.
• The angles may be different with respect to the workpiece after the tool is installed in the toolholder.

Rake Angle (γ)

• Controls chip flow direction and the strength of the tool tip.
• Positive Rake Angles (γ > 0):
  • Reduce cutting forces and temperatures, improving machining efficiency.
  • Result in a sharper tool tip, increasing the risk of chipping for brittle materials.
• Negative Rake Angles (γ < 0):
  • Strengthen the tool tip and extend tool life but require more cutting force.
  • Preferred for hard metals and interrupted cutting operations.

Back Rake Angle (BRA)

• Controls chip flow direction along the tool face.
• Higher angles reduce cutting force but weaken the tool edge.

Side Rake Angle (RA)

• More significant than BRA in determining cutting performance.
• Controls chip thickness and affects cutting force requirements.
• RA typically ranges from -5° to 5° for carbide inserts.

Cutting Edge Angle (β)

• Affects chip formation, tool strength, and cutting force distribution.
• Typically set to 15° for general turning.

Flank/Relief Angle (α)

• Prevents rubbing between the tool and workpiece.
• Too Large Increases chipping risk.
• Too small Causes excessive flank wear
• Usually set to 5° for general applications.

Nose Radius

• Affects surface finish and tool-tip strength.
• Smaller Nose Radius:
  • Produces rougher surface finish.
  • Reduces tool strength.
• Larger Nose Radius:
  • Enhances tool strength and improves surface finish.
  • Can cause chatter if cutting forces become too high.

Function Effects of Increasing or Decreasing the Angle

Rake Angle (γ):

• Controls the flow of chips and cutting forces.
• Increasing:Reduces cutting forces & temperatures, Improving chip evacuation, Increasing tool sharpness (but weakens the tip)
• Decreasing: Increases tool strength, Requires higher cutting forces, Generates more heat. Back Rake Angle (BRA):
• Directs chip flow along the tool face
• Increasing: Reduces cutting forces & Improves chip control
• Decreasing: Increases cutting forces & Strengthens cutting edges Side Rake Angle (RA):
• Determines chip thickness and flow direction.
• Increasing: Reduces cutting forces & Improves chip evacuation.
• Decreasing: Increases tool strength & Requires more force to cut. Cutting Edge Angle (6):
• Controls tool impact resistance and chip formation.
• Increasing: Increases tool strength & Reduces sudden tool wear
• Decreasing: Produces sharper cutting edges & Increases risk of tool chipping. Relief Angle (a):
• Prevents tool rubbing against the workpiece.
• Increasing: Reduces friction & Decreases heat generation.
• Decreasing: Increases tool strength & Causes rubbing and excessive heat. Nose Radius:
• Affects surface finish and tool durability.
• Increasing: Improves surface finish & Increases tool life and Reduces tool wear
• Decreasing: Produces sharper cutting edges & Rougher surface finish and Increases risk of tool chipping.

Cutting-Tools for Different Operations

• Turning Cutting-Tools, Threading tools & Drilling tools

Turning Operation Times

• Time estimation depends on the cutting length (L), the feed rate (f), and the spindle speed (n).
• Formula: tc = L/VF = L / f * n [min]
• Spindle speed (n) is related to cutting speed (Vc) and workpiece diameter (D):
  • n = 1000 Vc/pi * D
• Turning cutting velocity (vc or n)
  • Spindle speed n is dependent on cutting speed Vc and workpiece diameter D.
  • In a Manual LatheSpindle speed is constant and defined as: n = 1000 Vc/pi * D
• Numerically controlled (NC)
  • The system keeps Vc constant and adjusts n as D changes.
• Manueal Lathe
  • The spindle speed is set based on maximum work piece diameter (Dmax) as: n = 1000 Vc/pi * Dmax
• Differences (Manual & NC Lathes):
  • Manual n is fixed, whereasVc changes, the diameter Varies NC Vc remains constant and hence the n can adjust.
• FACING process
  • Moving outside diameter cutting tool toward the rotating workpiece
  • Requires Depends on operations of the lathe
• Time requires is dependent on lathe operation
  • Constant
  • Speedn, the (Rot) Speed Remains Constant.
  • Constant
  • Cutting Speed ,the machine Adjusts Inward to maintain Constant Cutting Velocity
• The cutting time can be Constant Vc
  • The spindle must have the proper speed
  • the cutting speed is from the based on the spindle speed R= workpiece Radius Vc= Cutting speed per MinVF= Feed Speed(mm\min) D= Exterior dam of The Work Piece: f= Feed Rate( mm \rev) n=Spindle speed
• FACING formula for Time Constant Vc for circular ring: tc = pi * (R2-r2)/1000 F *Vc (Spindle)

Cutting time in a straight turning

• machining a cylindrical workpiece along its axis removes material uniformly.
• the initial clearance c is typically small and neglected
• depends on feed rate f,machining length l
• calculated as follows: c= p * tan (G)
• formula: + l + c/f*n ≈ l/fn
• formula Spindle speed = n = 1000 * Vc/pi * D or in depth : n =N, whereas * f= depth per Cut (mm\rev) formula: tc =N. L/Fn = NL TD100 * Ve - where v= Constant 10 = LN/Dmed F100 =L N/1000 *Vc

Cutting time

• Threaded Operations
  • Thread cutting is a machining process that is used to create helical grooves and Cylindrical
  • Surfaces or threading surface is Cut and that is calculated using number of threader length, pitches.
• The Parameters are in (N₁) = D₁ *N = L. N t(TH) = [I ÷ c/DN] * Np ≈ LDN DP * Np where : l= total length DP= Adjected thread numbers, of the total passes and the spindle, the process on which is an estimated as: T(TH) = {L Np. ND, *D 1000 =Vc} The Thread is general smaller and we have to approximate some time

Cutting time Taper Turning

• Taper turning is a machining process that requires and increasing or decreasing a diameter it that will produce along the length of where is to be to be used shafting and spindles. And Conical parts are produced for Applications In Taper turning, where at each pass where to make the Lengths and which varies per Cut time, with the formula depend on
• Number and Precision L₁ = Conical Shapes i= material
• Per cutting Length on removalRate where C = ΣL/Σdn, =Σ(Σ p + /sin(y2)/an),
• And which equals d and y = L₁ = Conical Shapes i = materiel and d= per Σ

Tool Selection

• The machine has the following
• Tool Holder
• Tool Length
• Insert
• Parameters required for tool Holders or selection: I- Material to be machined and Ii- Type if turning & iii- milling, drilling etc and 4- Cutting Conditions 5- Shape to be obtained in turning.

Selection on following

I- Selection Material which requires

• a)
• II- type of applications And IV- to be obtained.

4. • The material being cut needs to follow criteria
5. Shape

Codes and tool selection

a) -Select a code that requires tool selection and the cutting, selection and the cutting tools needs. b) -Tool Holders c) -Tool type and size is code listed.

TOOL HOLDERS

-  The material is related to tool selections and which should to the correct holder, size and shape to produce high quality.