Cnc Tool Holding Devices 2k4b26

CncTOOL HOLDING DEVICES cnciti

INSERT & TOOL HOLDERS • TOOL HOLDING DEVICES • The tool holder system for machining centers shown in the figure is a modular toolingsystem. It consists of a basic tool holder, extension or reducer and tool adaptors. Tooladaptors are available for receiving various tools like milling cutters, drills reamers etc.Various methods of holding the tools are shown in figures. • • TOOLS AND TOOL MATERIALS USED IN CNC MACHINE . • The most important properties of the cutting tool material are:1.The material must withstand excessive wear even though the relative hardness of the tool materials changes. • 2.Ability to retain hardness under severe working condition.3.Ability to withstand cutting forces.4.The frictional coefficient must remain low for minimum wear and reasonable surfacefinish.5.Cost and easiness of fabrication should have within reasonable limits.

TYPE OF TOOL MATERIALCARBON STEELS • • • • • • • • • • • • •

It may only be used in manufacture of tools operating at low cutting speed (12mt/min). • Disadvantages of carbon tool steel are they are comparatively low heat and wear resistance. HIGH-SPEED STEEL (HSS) • HSS operate at cutting speeds 2 to 3 times higher than for carbon steels and retain their hardness up to 900c. • Three general types of HSS are high tungsten, high molybdenum and high cobalt. • Tungsten in HSS provides hot hardness and form stability. Molybdenum maintainskeenness of the cutting edge. Cobalt makes the cutting tool more wear resistance.

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STELLITES • Stellite is the trade name of a non-ferrous cast alloy composed of cobalt, chromium andtungsten. • They are used for non-metal cutting application such as rubbers plastics etc. CARBIDESa)Solid Carbidesb)Inserts. • They are composed principally of carbon mixed with other elements.

The basic ingredient of most carbide is tungsten carbide that is extremely hard, puretungsten powder is mixed under high hear (1500c) with pure carbon in the ratio of 94% and6% weight.

The two types of carbides are the tungsten and titanium and both are more wear resistant Carbides are designed for machining tougher materials chiefly for various materials.

• COATED CARBIDES • • The coated carbide has substrate and coating layer. • • Substrate for toughness having hard materials and soft materials (cobalt + carbides) • • Coating layer of carbide (very hard) • • Better impact strength to resist fracture. • MODERN COATING • This layer of coating reduces friction between chip and tool and time duration is verylimited.Modern coating (Multi Layer)Coating processChemical vapour deposition.Physical vapour deposition.Plasma CVD coating. • COATED CEMENTED CARBIDES • The cemented carbides with a very thin coat of carbides. The layers of titanium carbideswere only a few microns thick and increase the performance of carbide tools.

• COATED CARBIDES (GC) • More than 75% of turning operations and more than 40% of milling operations are todayperformed with coated carbides.The main coating materials are • • Titanium carbide (Tic) • • Titanium nitride (Tin) • • Aluminum oxide ceramic (Al203) and • • Titanium carbon nitride (TiCN)