Cutting-Tool Types: Integral, Welded, Insert

Cutting-Tool Types

• Integral Tools: The whole tool comprises cutting-tool material, especially high-speed steel (HSS).
• Integral tools are durable but require resharpening.
• Welded Insert Tools: Only the insert comprises cutting-tool material like carbide or ceramics, welded permanently to the toolholder.
• These tools balance cost and performance.
• Interchangeable Insert Tools: The insert, made of hard metals or ceramics, is replaceable without sharpening.
• Interchangeable Insert Tools are widely used in high-precision machining, including aerospace work.

Integral Tools

• Materials include high-speed steel (HSS) or carbide, made from square or round bars by grinding or forging.
• Less common currently, but still useful for:
• Custom tool profiles in shaping.
• Low-cost machining requiring infrequent tool replacement.
• Precision form cutting in prototyping.
• Orientation comes in right or left-hand based on the cutting direction.
• Types of integral tools for:
  • 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

• Material: Composed of a steel tool body with a carbide or ceramic insert welded onto the cutting edge.
• Offers more wear resistance than integral tools.
• Welded Insert Tools are more rigid and stable than interchangeable inserts.
• Lower costs compared to fully carbide tools.
• Cannot be replaced when worn, needing regrinding or discarding.
• Not ideal for high-speed machining due to heat accumulation.
• Used in medium-production settings where tool life is key and replacement costs must stay minimized.
• Suited for custom tool geometries not available as interchangeable inserts.
• Types include:
• Turning tools (ISO 1, 2, 6).
• Tip tools.
• Tools angled to the left.
• Tools angled to the right (ISO 3).
• Front cutting tools (ISO 5).
• Interior tools (ISO 8, 9).
• Tools for grooving (ISO 4, 7).

Interchangeable Insert Tools

• These are the most common modern machining cutting tools, especially in high-speed and precision turning.
• Formed by a handle/support, plus an insert fixed to allow exchange once worn (not sharpened).
• Inserts usually comprise carbide, cermet, ceramic, or polycrystalline diamond (PCD) for advanced machining.
• They give superior performance, longer tool life, and quick insert replacement, cutting downtime.
• Clamping system types consist of:
• Flange: Easy to change, but less secure for high speeds.
• Screw: More compact and highly stable, but takes longer to replace.
• Lever: Quick insert changes, but applies uneven stress, causing insert failure in challenging jobs.

Cutting-Tool Type Comparison

• Integral Tools:

• Made from single piece of HSS or carbide

• Can be resharpened.

• Lower durability

• Low initial cost

• Limited speed - good for low speed use

• Slow tool change, re-grinding needed

• Good for prototyping

• Welded Insert Tools:

  • Steel body and carbide/ceramic tip.
  • Can be reground.
  • Higher durability than Integral tools but lower than Interchangeable
  • Medium Cost.
  • Moderate Speed, worry about buildup of heat.
  • Moderate Tool Change speed.

• Interchangeable Insert Tools

  • Made of steel or carbide with replaceable inserts.
  • Cannot be sharpened.
  • Longest Lifespan.
  • High Initial Cost, but cost effective.
  • Excellent for high speed.
  • Fast Tool Change.

Cutting-Tool Geometry

• Most turning uses single point cutting tools with typical right-hand cutting tool geometry.
• Various angles in a single-point cutting tool perform important functions in cutting performance, affecting cutting forces, chip flow, heat creation, and tool wear.
• Angles may differ regarding the workpiece.

Rake Angle (γ)

• Controls chip flow direction and tool tip strength.
• Positive rake angles (>0):
• Reduce cutting forces and temperatures.
• Increase chipping risk for brittle materials.
• Negative rake angles (<0):
• Strengthen the tool tip.
• Useful for hard metals and interrupted cuts.

Back Rake Angle (BRA)

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

Side Rake Angle (RA)

• Is more important than BRA for determining how well the cutting happens.
• Controls chip thickness and the cutting force needs.
• RA ranges from -5° to 5° for carbide inserts.

Cutting Edge Angle (β)

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

Flank/Relief Angle (α)

• Prevents rubbing between the tool and the workpiece.
• If too large, it increases the risk of chipping.
• If too small, it causes excessive flank wear.
• Set to 5° for general use.

Nose Radius

• Affects surface finish and tool-tip strength.
• Smaller nose radius:
• Creates a rougher surface finish.
• Reduces tool strength.
• Larger nose radius:
• Enhances tool strength and surface finish.
• Triggers chatter if cutting forces get too high.

Tool Geometry Summary

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

Cutting-Tools for Different Operations

• Turning Cutting-Tools come in various types:
• Cutting Off, Back Turning, and Grooving
• Front Turning, Threading, and Boring

Turning Operation Times

• The time needed to complete a turning operation depends on:
• Cutting length (L).
• Feed rate (f).
• Spindle speed (n).
• The general formula is: tc = L / VF = L / f * n [min]
• Spindle speed (n) relates to the cutting speed (Vc) and diameter (D): n = 1000 * Vc / (π * D) Tc= L * π * D / f * 1000 * Ve

Cutting Velocity - Constant Vc or n

• Spindle speed (n) depends on the cutting speed (Vc) and diameter (D). For manual lathes, the spindle speed is constant.
• Formula: n = 1000* Vc/ π * D
• For a controlled (NC) setting the Vc stays the same but (n) changes.
• For manual machines (n) is based on a set maximum diameter value (Dmax).
• Formula: n = 1000* Vc/ π * Dmax
• For manual versions the (n) stays steady and the Vc changes when the diameter varies.
• (NC) lathes keep the Vc steady, so adjustments to (n) happen normally.

Cutting Time in a Facing Process

• Facing: Moving the cutting tool from the outer diameter into centre of rotating material.
• Time needed relies on the lathe working with:
• Constant spindle speed (n), implies rotational rate stays still.
• Constant cutting speed (Vc), tells of the machine setting the ‘nnn’ as tool moves inward.

Constant (n)

• Determines the cutting time derived from feed rate and spindle speed.
• If circular surface, formula is condensed down.

Constant (Vc)

• For determining the cutting time, the speed is set on the average spindle speed when variations in diameter are present.

Straight Turning Time

• Depends on the length (I), the feed rate (f) and the speed.
• Set by the depth of the cut (p) and also the angle of inclination (G).

Threaded

• Relies on the length, the pitch(dp), the number of passes (Np) and the speed
• Time is calculated by number of passes * pi * diameter divided by the pitch and 1000 * Vc

Taper turning

• Time varies based on length, number of passes, depth, and the cone angle

Tool Selection

• Criteria for tool selection
• Material
• Steel (ISO P), Stainless Steel (ISO M), Cast iron (ISO K), Aluminium alloys (ISO N), Heat resistant alloys (ISO S), Hardened steel (ISO H)
• Type of application (Turning, milling, drilling...)
  • Determined by roughing (H - Operations for max stock removal) , Medium Machining (M - For general purpose), and Finishing (L - Ops that operate at light DOC)
• Other considerations
  • What kind of machine? (Good - High Speed Cuts, Average: Medium cut speeds, Difficult - Low cut speeds)
  • Shape and Size (Tool holder size)
  • Tool type code (CNMG09)