Types of tool wear during turning

Types of tool wear during turning, defective parts and ways to eliminate them

FORMATION OF A GROWTH ON THE CUTTING EDGE

Description and reasons: We are talking about grasping the processed material with the cutting edge of the tool. The growth has the character of a deposited metal on the cutting edge. If it breaks, the cutting edge of the tool may be discolored. This phenomenon is characterized by a decrease in the quality of the treated surface

Recommendations:

• change (increase) cutting speed

• change (increase) the feed

• apply coated types of hard alloy

• apply a different cutting geometry

• apply a coolant with a higher action against the formation of a build-up (in its absence, refuse cooling) 

WEAR ON THE BACK SURFACE 

Description and reasons: Wear on the back surface is one of the main criteria characterizing the service life of the SMP. It occurs as a result of the contact of the SMP material and the processed material during the cutting process. Its size (intensity) can only be reduced.  

Recommendations:

• apply a more wear-resistant type of hard alloy

• reduce the cutting speed

• increase the feed (if the feed is less than 0.1 mm/tooth)

• apply coolant or increase the cooling intensity

THE HOLE ON THE FRONT SURFACE 

Description and reasons: Hole formation is a type of wear that is most pronounced in SMP without chip–breaking grooves, but is not limited only to this type пластин. When processing soft materials, a wider and smaller hole is formed, and, conversely, when processing harder materials, a narrow and deep hole is formed. 

Recommendations:

• apply a more wear-resistant type of hard alloy

• apply a hard alloy with a coating, first of all, MT CVD

• reduce the cutting speed - apply a different, more positive type of cutting geometry

• apply coolant or increase the cooling intensity;

THE GROOVE ON THE AUXILIARY CUTTING EDGE 

Description and reasons: The oxidizing groove on the auxiliary cutting edge is one of the main criteria that reduces the life of the SMP. It appears mainly in the process of turning. The connection of the oxidizing groove with the hole on the front surface repeatedly increases the roughness of the treated surface. 

Recommendations:

• apply a coated hard alloy or a more wear-resistant type of hard alloy, if conditions allow

• apply SMP with a coating containing Al2O3

• apply coolant or increase the cooling intensity

• reduce the cutting speed;

PLASTIC DEFORMATION OF THE VERTEX;

Description and reasons: Plastic deformation of the top – the cause of this type of wear is the overload of the cutting edge as a result of exposure to high temperatures in the cutting zone (high cutting speeds and feeds). 

Recommendations:

• apply a more wear-resistant type of hard alloy;

• reduce the cutting speed

• reduce the feed

• apply coolant or increase the cooling intensity

• apply a NSR with a large radius of rounding the vertex

• apply a SMP with a large angle at the top;

THE GROOVE ON THE MAIN CUTTING EDGE 

Description and reasons: The groove on the main cutting edge occurs in the area of the "first contact" of the cutting edge of the tool with the surface of the workpiece. This type of wear occurs, as a rule, when processing corrosion-resistant austenitic steels (during processing, the surface layers of the workpiece material are hardened). 

Recommendations:

• apply a hard alloy with a coating or a more wear-resistant type of hard alloy, if conditions allow

• apply SMP with a coating containing Al2O3

• choose a tool with a smaller angle in the plan

• process with variable cutting depth (along the cone)

PAINTING OF THE CUTTING EDGE;

Description and reasons: The chipping of the cutting edge occurs, in most cases, in combination with a different type of wear, it is difficult to identify it independently. 

Recommendations:

• apply a more viscous type of hard alloy;

• choose less intensive cutting conditions

• apply a different cutting geometry

• when cutting in, reduce the feed

• change the way the tool enters and exits when cutting;

DESTRUCTION OF THE CUTTING EDGE (OUTSIDE THE CUTTING AREA) 

Description and reasons: Destruction of the cutting edge (outside the embedding) – the reason for this is an unsatisfactory chip crushing process - the direction of the chip coming off, which, when it is withdrawn, "touches" the cutting edge and damages it. 

Recommendations:

• change the feed

• choose a tool with a different main angle in the plan;

• apply a different cutting geometry (a different chip breaker)

• apply a more viscous type of hard alloy;

THERMAL CRACKS 

Description and causes: Thermal cracks are a consequence of dynamic thermal load during intermittent cutting.  

Recommendations:

• refuse liquid cooling (air can be used to eliminate chips from the cutting area) 

• choose a more viscous SMP material

• reduce the cutting speed;

FATIGUE CRACKS;

Description and causes: Fatigue cracks occur as a result of dynamic loading of the area directly behind the cutting edge. 

Recommendations:

• apply a more viscous type of hard alloy;

• will change the way the tool enters and exits the workpiece

• change the embedding conditions

• apply a different type of cutting geometry or a different shape of the NSR (...T, ....S, ....K, ....P) 

PAINTING THE CUTTING EDGE OR THE TOP OF THE TOOL;

Description and reasons: The coloring of the cutting edge or the top of the tool - the causes of this phenomenon can be very diverse and depend on the state of the material of the tool and the workpiece, and, in particular, the rigidity of the "machine – tool – workpiece" system and the conditions of embedding. 

Recommendations:

• apply a more viscous type of hard alloy;

• choose less intensive cutting conditions (reduce feed and depth)

• apply a NSR with a large radius of rounding the vertex

• apply the SMP with a large angle at the top

• apply a different cutting geometry (a different chip breaker)

• stabilize the cutting edge (cutting edge)

• reduce the feed when cutting 

BURR FORMATION;

Description and reasons: This phenomenon is very common, but it can not always be prevented. Burr occurs primarily in the processing of soft steels and plastically deformable materials. 

Recommendations:

• apply SMP with a sharp cutting edge;

• apply SMP with positive geometry

• apply a tool with a smaller angle in the plan;

INACCURACY OF THE SIZE AND SHAPE OF THE WORKPIECE;

Description and reasons: It arises as a result of a large number of factors, or the properties of the "machine – tool – workpiece" system. 

Recommendations:

• select СМП with sufficient wear resistance;

• check the reliability of fixing the workpiece

• check the reliability of fixing the tool (reduce overhang or eliminate imbalance)

• choose the appropriate size of the allowance for processing;

UNSATISFACTORY CHIP FORMATION;

Description and reasons: Acceptable chip shape is currently as important a criterion as the service life of the plate itself. The chip crushing process is influenced by: the material of the workpiece, feed, cutting depth, and, of course, the appropriate choice of cutting geometry (chip breaker). Long (unformed) chips are unacceptable for many reasons, as well as too short - very finely "fragmented" chips are undesirable - this indicates an overload of the cutting edge and the possibility of vibrations.

Recommendations:

• change the feed and cutting depth;

• choose a more suitable geometry

• change the embedding conditions;

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GENERAL RECOMMENDATIONS;

Control of the correct fit of the NSR in the socket. Before installing a new SMP or changing the cutting edge, it is necessary to clean the seat, check its condition - there is no damage to the wedge and the backing plate. 

Control and repair of fasteners. It is important to control the fasteners themselves: the angle lever, screw, tack or clamping wedge. Only undamaged elements should be used for fastening, in case of their replacement, only spare parts that are listed in the catalog of this tool should be used. Regularly lubricate the thread and the conical bearing surface of the screws with grease resistant to elevated temperatures, for example, Molykote G. When mounting or disassembling, use only screwdrivers and keys specified in the catalog and recommended by the tool manufacturer. It is necessary to tighten all screws using a torque wrench. 

Pinning control. When fixing the NSR, it is necessary to check its tight fit over the entire support surface and the emphasis - in the radial and axial directions. Fixed SMPS and tools must always be clean and undamaged. 

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Sandvik materials were used, Pramet.

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