Fundamentals Of Machining Flashcards
State common machining operation
- Turning - work piece rotate, curring tool layers of material as it move to the left.
- slab Milling - rotating cutting tool remove material from surface
- end milling - rotating cutter travel along a depht in work piece producing cavity.
- cutting - tool move radially inward removing piece from bulk of blank
Define turning
Tool set to a cutting dept, move from right to left at a certain feed rate (mm/rev)
Common term in cutting process diagram
Rake angle (a) , relief angle (@), depth of cut, depth of chip, flank, shear angle
Factor influencing machining op
Chips, temp, cut spd/depth/feed/fluid, angle, wear, machinibility
Major independent variable
Tool material/coat/shape/surface finish/sharpness/characteristic, workpiece material and condition, cutting spd/feed/depth/fuild, workholding/fixturing.
Cutting ratio
r= To/Tc =sin @/ cos (@-a)
Shear angle preditions
@ = 45 + a/2 -b/2
b = friction angle
Velocity of chip
Vc = vsin@/ cos(@-a)
Shear velocity
Vs = Vcosa/cos(@-a)
Continous chip
- From high rake angle and/or high cutting spf.
- good surface finish
- bad for auto (tangled)
Built up edges chip
- from layers of material deposited onto tool
- breaks up eventually and carried awy to side of tool
- deposited randomly on surface
- poor surface finish
- prevent by increasing rake angle which decrease depth of cut
Discontinued chip
-from hard brittle material
- segments may be firmly or losely attached
- brittle failure takes place along shear plane before plastic flow occurs
- occurs from low rake angle (large depth of cut)
Serrated chips
-semi continuous chips with low and high shear strain
- from low thermal conductivity and strength metals
Chip breaker
-cuts chip
- can be build in or is a piece of metal
Relationship between angle of oblique tool and chips
As angle increase, chips becomes more tightly curled
