GATE Past Year Questions: Machining Parameters | Manufacturing Engineering - Mechanical Engineering PDF Download

Should be cut by negative SCEA.

Gray Cast Iron because of its damping nature and characteristic to absorb shock.

Molybdenum and Tungsten both increases hot hardness & abrasion Resistance.

Hot Hardness is the property of tool material to withstand at higher temperature with hardness.

10 : 20 : 10 : 5–10 Maximum heat generated must goes with chip and remaining goes to workplace & tool least goes to the Environment.

Detoriation of surface finish

Carbide tool are ceramics, which are having low toughness. So negative rakes angles are used.

Z = teeth table feed = 40 mm / min
N = 100 rpm

f_t = 0.05 mm

Chatter in every 30° .
So 12 chatter mark in one revolution.

Soft tool material must be used in order to avoid tool wear.

For, orthogonal turning,
λ = 90°, F_c = 1601 N
Chip thickness 't_c' = 0.3,
F_t = 1259 N.
N = 1000 r pm , α = 10 m

= 1601 x cos19.19° - 1259 sin 19.19
= 1098.20 N

Specific cutting pressure

By increasing the cutting speed, heat dissipation is increased so maximum temperature is decreased. Hence coefficient of friction is decreased.

BUE is formed while machining ductile materials at low speed.

Wear rate is proportional to tan y, i.e.
Wear rate ∝ tan y
Where, y  = Clearance angle
When clearance angle is decreased from 10° to 7°, then

= 30.37 % decrease.

Nose Radius = 1 – 8 mm, f = ?
R_t = 5 microns
(Peak  to valley height)

f = 0.268 mm/rev

α = 10°, ϕ= 20°
Ernest & Merchants' theory
2ϕ + β - α = 90°
2 × 20 + β - 10 = 90°
40 + β - 10 = 90°
β = 60°

Vanadium increases the wear resistance of High speed steel.

Chip takes away heat from the working zone otherwise tool life and work piece surface finish would get spoiled.

Maximum temperature at the chip tool interface is 2 – 3 mm away from cutting edge because shank provides rapid heat dissipation just below the cutting edge.