CUTTING TOOL MATERIALS & CUTTING FLUIDS Chapter – 21 Introduction Carbon and medium alloy steels High speed steels Cast-cobalt alloys Carbides Coated tools Alumna-based ceramics Cubic Boron Nitride Silicon Nitride based ceramics Diamond Whisker-reinforced tool materials
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& CUTTING FLUIDS
Chapter – 21
Characteristics of cutting tool :
High speed steels (HSS)
M-series - Contains 10% molybdenum, chromium, vanadium, tungsten, cobalt
T-series - 12 % - 18 % tungsten, chromium, vanadium & cobalt
30%- 33% chromium
3-groups of materials
2-groups of carbides used for machining operations
Fig : Methods of attaching inserts to toolholders : (a) Clamping and (b) Wing lockpins. (c) Examples of inserts attached to toolholders with threadless lockpins, which are secured with side screws.
Fig : Relative edge strength and tendency for chipping and breaking of inserts with various shapes. Strength refers to the cutting edge shown by the included angles.
Fig : edge preparation of inserts to improve edge strength.
Unique Properties :
Techniques used :
Plasma assisted CVD
Fig : Ranges of properties for various groups of tool materials.
Titanium nitride (TiN) coating :
Titanium carbide (TiC) coating:
Multi Phase Coatings :
Fig : Multiphase coatings on a tungsten-carbide substrate. Three alternating layers of aluminum oxide are separated by very thin layers of titanium nitride. Inserts with as many as thirteen layers of coatings have been made. Coating thick nesses are typically in the range of 2 to 10 µm.
Ion Implementation :
Cermets, Black or Hot- Pressed :
Fig : (a) Construction of a polycrystalline cubic boron nitride or a diamond layer on a tungsten-carbide insert. (b) Inserts with polycrystalline cubic boron nitride tips (top row) and solid polycrystalline CBN inserts (bottom row).
New tool materials with enhanced properties :
Cutting Fluids: (Lubricants + Coolants)
Used in machining as well as abrasive machining processes
Fig : Schematic illustration of proper methods of applying cutting fluids in various machining operations: (a)turning, (b)milling, (c)thread grinding, and (d)drilling