Turning Operations: Tool Selection

• The objective is to utilize catalogs and programs for tool selection.
• Selection criteria depends on turning operations to select the most suitable tool.

Factors to consider when selecting a tool

• Piece material, properties, and machinability
  • Tool quality and geometry
  • Machining conditions.
• Part profile
  • Shape of the tool holder
  • Insert clamping system.
• Type of operation
  • External or internal roughing, grooving, finishing, etc.
  • Tool holder shape
  • Insert clamping system
  • Machining conditions.

Geometric aspects of the edge in a single-edged tool

• Includes the secondary edge, principal edge
• Includes the nose, upper surface of the tool
• Auxiliary clearance face, and principal clearance face.
• Tools angles include:
  • Clearance angle
  • Cutting edge angle
  • Rake angle.

Tool Material Angles

• Very hard cast iron, brasses, and hard bronzes:
  • α (clearance angle) is 6°
  • β (wedge angle) is 84°
  • γ (rake angle) is 0°.
• Extra-hard steel, hard cast iron, bronze, brass:
  • α is 6°
  • β is 76°
  • γ is 8°.
• Hard steel, soft cast iron, soft brass:
  • α is 8°
  • β is 68°
  • γ is 14°.
• Soft steel:
  • α is 8°
  • β is 62°
  • γ is 20°.
• Very soft steel, soft bronze:
  • α is 8°
  • β is 54°
  • γ is 28°.
• Light alloys and plastic materials:
  • α is 10°
  • β is 40°
  • γ is 40°.

Different tool shapes are useful

• Tool for circular point grooving
• Round nosed tool
• Tool for cutting from below/grooving
• Right tool for facing or trimming
• Right tool for roughing and turning
• Right tool for finishing.
• 60° tool for threading.

Analyzing Carbide Material (Inserts)

• Blue inserts are used for steels with carbon (C) and alloyed steels.
• Yellow inserts are applicable to stainless steels, titanium, high-temperature alloys, and gray and ductile cast irons.
• Red inserts are for aluminum and non-ferrous materials.

Tool insert color codes for turning

Blue P inserts:

• Used for machining long-chipping materials like steel and malleable cast iron.
  • P01: Finishing and boring at high cutting speed, small chip section, high surface finish, tight tolerances, free of vibrations.
  • P10: Turning, copying, threading, milling at high cutting speed, small to medium chip section.
  • P20: Turning, copying, milling at medium cutting speed, medium chip section, moderately unfavorable conditions.
  • P30: Turning, milling at medium to low cutting speed, medium to long chip section, unfavorable cutting conditions.
  • P40: Turning, milling, grooving, parting, planing at low speed, large chip section, very unfavorable working conditions.
  • P50: High toughness is required in turning, planing, grooving and parting.

Red K inserts

• Used for machining short-chipping materials such as gray cast iron and non-ferrous materials like aluminum, bronze, and plastics.
  • K01: Turning, finish turning, boring, and finish milling.
  • K10: Turning, milling, boring, reaming, etc.
  • K20: Turning, milling, planing, boring, broaching, operations requiring very tough tools.
  • K30: Turning, milling, planing, boring, grooving, unfavorable conditions.
  • K40: Turning, milling, planing, parting and highly unfavorable machining conditions.

Yellow M inserts

• Applicable in machining harder materials like austenitic stainless steel, heat-resistant materials, manganese steel, alloyed iron, etc.
  • M10: Turning at medium to high cutting speed, small to medium chip section.
  • M20: Turning, milling at medium cutting speed, medium chip section.
  • M30: Turning, milling, planing at medium cutting speed, large chip section.
  • M40: Turning, profile turning, parting, especially in automatic machines.

Tool Selection Process

• Selecting the insert clamping system.
• Determining the tool holder size and type.
• Choosing the insert shape, size, and nose radius.
• Selecting the quality of the insert.
• Factoring cut data and giving practical advice.

Insert Clamping Systems

• Lever Lock (P) system
  • Offers excellent stability and high positional accuracy
  • Good repeatability
  • Does not obstruct chip flow
  • Allows quick and easy insert changes
  • Suitable for external turning and boring of large holes.
• Clamp Lock (C)
  • Applied in external and internal precision finishing operations.
  • Special designs in the clamp and/or insert enable high-precision copy machining.
• Screw Lock (S)
  • Accommodates a wide variety of inserts with secure clamping and excellent repeatability.
  • Chip flow is uninhibited.
  • Requires minimal space.
  • Used in small diameter internal machining
  • Light external roughing to finishing small parts.
• Top Clamp Lock (M)
  • Characterized by high rigidity, excellent stability
  • Highly accurate positioning, and good repeatability
  • More accessible for external copying operations.

Clamping Method Selection

• For roughing with screw and clamp: 3 (most appropriate).
• For finishing 2 is the appropriate choice.
• For roughing with clamp lock: 3 is the appropriate choice.
• For finishing choose 2.
• For roughing with lever Lock: 1 is appropriate.
• For finishing applications 3 is the value.
• For roughing with screw lock: 1 is appropriate.
• And likewise for finishing select 3.
• Double-sided inserts are paired with screw and clamp.
• Single sided inserts with chip breakers are used in for brace lock and lever lock clamping.
• Lisa inserts with screw lock.

Boring Bar Clamping System Characteristics

• Bore operations are sensitive to hole diameter and length
• Cutting forces tend to displace the tool creating vibration, and flexion.
• Select the largest possible diameter alongside the shortest possible overhang.
• Surface requirements include support:
  • Ra = 0.8 µm
  • Hardness 45 HRC
  • Tolerance H8
  • Solid bars
  • Anti-vibration bars.

Different Clamping Methods

• Solid bar, providing optimal clamping.
• Tool holder, offering good clamping.
• V-shaped holder with screws are other clamping options, but they offer poor clamping quality.
• Cylindrical tool holder, also offering poor clamping quality.

Boring System Vibration Settings

• Low: Use a 90° position angle.
• High: Adjust to 75° position angle.
• Low: Use a 0.2mm Tip Radius.
• High: Adjust to the values on the image.
• Adjust inclination angles accordingly.

Tool Holder Size and Type

• Influenced by the angle of the cut
• Affected by the direction of cut.
• Affected by the required rigidity, and shank dimensions.
• Selection depends on:
  • Direction of feed
  • Depth of cut
  • Shape of the part to be machined
  • Accessibility of the tool on the part.
• Choose the largest possible size with the smallest position angle.

Toolholder Types

• Outer holders for roughing have a particular geometry relating to the direction of the arrows in the image.
• Outer holders for finishing also have a geometric layout.
• Inner Toolholders, etc.

Insert Shape Affecting Factors

• Positional angle.
• Required accessibility.
• Required Versatility.
• Larger point angles offer greater resistance and economy.

Insert Shape Comparison Values

• Round inserts (R) provide the highest tenacity and lowest accessibility.
• 90° square inserts have good tenacity but lower scores for finish than round inserts.
• 80° rhombus inserts have good tenacity and versatile operability.
• 60° triangle inserts have good performance for turning and facing but are otherwise limited.
• 55° rhombus inserts offer a good combination of characteristics.
• 35° rhombus inserts offer the greatest accesibility.

Inserts to consider when machining a work piece

• Round (R) inserts are suited to roughing (tenacity).
• Square inserts are suited to light roughing /semi-finishing.
• Shaped inserts are suited to finishing.
• Shaped inserts are used in turning and facing (feed directions).
• Rhombus inserts may be used when profiling.
• Rhombus inserts offer versatile operation, and material hardness.

Length Dimensions of inserts

• The length of the effective cutting edge.
• Determine the highest value for ap.
• Then calculate leffect ≥ a / sen K.

Effective cutting edge length

• la = 0.4d
• la = 2/31
• la = 1/2 1
• la = 1/4 1

Cutting Edge Radius

Roughing

• Employ the largest radius possible for a more robust cutting edge and to facilitate a higher feed rate.
• Using a small radius is recommended if vibrations are an issue.
• Empirical relation is f = 0.5 r.
• Max relation is f= (2/3) r.
• The chart in this section outlines the relationship between point radius (mm) and max feed (mm/rev).

Finishing

• Relies on:
  • Feed
  • Cutting edge radius
  • General machine conditions.
• Progress through:
  • Increased cut velocities
  • Positive disengagement angle.
  • Reduced Radii
  • Non-coated Tools.

Cutting area types for external turning

• A= Extreme finishing - f = 0.05 - 0.15; ap = 0.25 - 2.0
• B = Finishing - f = 0.1 - 0.3; ap = 0.5 - 2.0
• C = Light roughing - f = 0.2 - 0.5; ap = 2.0 - 4.0
• D= Roughing - f = 0.4 -1.0; ap = 4.0 - 10.0
• E= Heavy roughing - f = > 1.0; ap = 6.0 - 20.0
• F= Very heavy roughing - f = > 0.7; ap = 8.0 - 20.0

Data depends on

• Cutting material
• Area of work
• Part material.
• Nominal values are per the manufacturer.
• Correct based on the material and tool life.

Practical Advice

• Follow these steps when making selections
  • Material of the piece. (PMK)
  • Qualitative insert characteristics
  • Type of application.
  • Exterior/interior grooving, parting, copying or tapping.
  • Type of pass- finshing, medium, roughing
  • Favorable, normal or difficult cutting conditions.
  • Part Parameters- machine piece.
  • Geometry of the insert.
  • Geometry of the cutting edge
  • Angle and size of hte tool holder.

Productivity Improvement Considerations and Methods

• Streamline Tool Inventory Simplify the types of tools inventoried to cover most situations and reduce waste.
• Adjust cutting data versus tool life +50% life of the tool. +20% cutting data.
• Use dry machining.
• Cut coolant costs.
• Use scraper inserts. and modular quick change tooling systems.