Section N 25-26

Technical Guidance Chip Control and Countermeasures, Turning Edition

■ Type of Chip Generation Flowing Shearing

■ Type of Chip Control

Depth of cut

A

B

C

D

E

Tearing

Cracking

Large

Classification of chip shapes

Work Material

Work Material

Work Material

Work Material

Small

Continuous chips with good surface finish General cutting of steel and light alloy

Chip is sheared and separated by the shear angle Steel, stainless steel (low speed)

Chips appear to be torn from the surface Steel, cast iron (very low speed, very small feed rate)

Chips crack before reaching the cutting point Cutting of general cast iron and carbon

NC lathe (for automation) General-purpose lathe (for safety)

H H S S J

H S S S to J H

N

Good: C type, D type

Large Large Small Large

Deformation of work material Rake angle Depth of cut Cutting speed

Small Small Large Small

A type: Twines around the tool or workpiece, damaging the machined surface and affecting safety B type: Causes problems in the automatic chip conveyor and chipping occurs easily E type: Causes spraying of chips and poor surface finish due to chattering, along with chipping, large cutting force and high temperatures {

Poor

■ Factor of Improvement of Chip Control (1) Increase feed rate ( f )

.1575

t 1

t 2

f 2

f 1

.0787

f: : When f 2 > f 1, t 2 > t 1

When the feed rate increases, the chip thickness (t) increases and chip control improves.

.0039

.0079

.0118

.0157

0197

Feed Rate f (IPR)

(2) Decrease side cutting edge ( : )

θ 2 :

θ 1 :

45°

t 1

t 2

f

f

: When : 2 < : 1 , t 2 > t 1

15°

Even if the feed rate is the same, a smaller side cutting edge angle makes chips thicker and chip control improves.

.0079

.0098

.0118

.01378

Feed Rate f (IPR)

(3) Reduce nose radius (RE)

t 2

t 1

.0630

RE2

RE1

Corner Small radius

Corner Large radius

f

f

RE : When RE2 < RE1, t 2 > t 1

.0315

Even if the feed rate is the same, a smaller nose radius makes chips thicker and chip control improves. * Cutting force increases proportionately to the length of the contact surface. Therefore, a larger nose radius increases back force which induces chattering. A smaller nose radius produces a rougher surface finish at the same feed rate.

.0157

.0197

.0394

.0591

.0787

Depth of Cut a p (inch)

N39

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