How to Use a Tool and Cutter Grinder

A tool and cutter grinder is used to sharpen the edges of tools that have gone dull. The tool and cutter grinder is not a toy and takes special care and training in order to operate correctly. The tool and cutter grinder is also a rather large machine found in machine shops. It is recommended to take your tools to a professional to grind and sharpen them. The following article will explain how a professional operates a tool and cutter grinder machine.

Step 1 - Prime the Machine

It is always a good idea to turn the tool and cutter grinder on to warm it up. A cold grinder will create rough cuts while a warm or hot grinder disc will produce the best result. Allow the tool and cutter grinder to run for several minutes before taking tool to the grinding disc.

Step 2 - Safety Precautions

Just looking at the tool and cutter grinder suggests a medieval torture device. There are a lot of moving parts, guides and rails to worry about as well as the grinding disc itself. Always wear heavy work gloves when using the machine. You also need to wear safety goggles. The grinding disc is typically abrasive and made with diamonds. When grinder begins to sharpen the tool it can cause small fragments of the tool, the disc or sparks to fly toward your face. Getting any of these superheated fragments in your eye can be very dangerous.

Step 3 - Examine the Tool

Not all tools are made the same and it is important to examine the tool you are about to use the tool and grinder cutter on. You are looking for the angle of the tool, including which way the blade is curved, how the edges are cut and the contact points. This is incredibly important because to properly use the tool and cutter grinder you need to know what direction the tool needs to go. If you fail to do this, you can severely damage the tool you are trying to bring back to life.

Step 4 - Using the Tool and Cutter Grinder

Double check all of your safety areas and examine your clearance. The kind of tool you are using will determine what the settings need to be. For this information you should always consult the instruction manual that came with the machine you have access to. Not every tool and cutter grinder is the same when it comes to this. Turn the machine on and keep a safe distance from the grinding disc. Remember the curvature of the tool you are sharpening and place it against the grinding disc at the appropriate angle. A knife, for example, would be approximately 45 degrees. Use short movements and firm pressure until you are satisfied it is sharp.

Tool and cutter grinder

A tool and cutter grinder is used to sharpen milling cutters and tool bits along with a host of other cutting tools.
It is an extremely versatile machine used to perform a variety of grinding operations: surface, cylindrical, or complex shapes. The image shows a manually operated setup, however highly automated Computer Numerical Control (CNC) machines are becoming increasingly common due to the complexities involved in the process.
The operation of this machine (in particular, the manually operated variety) requires a high level of skill. The two main skills needed are understanding of the relationship between the grinding wheel and the metal being cut and knowledge of tool geometry. The illustrated set-up is only one of many combinations available. The huge variety in shapes and types of machining cutters requires flexibility in usage. A variety of dedicated fixtures are included that allow cylindrical grinding operations or complex angles to be ground. The vise shown can swivel in three planes.
The table moves longitudinally and laterally, the head can swivel as well as being adjustable in the horizontal plane, as visible in the first image. This flexibility in the head allows the critical clearance angles required by the various cutters to be achieved.

CNC tool and cutter grinder

A modern CNC tool grinder with automatic wheel pack exchanger and tool loading capabilities.

Today's tool and cutter grinder is typically a CNC machine tool, usually 5 axes, which produces endmills, drills, step tools, etc. which are widely used in the metal cutting and woodworking industries.

Modern CNC tool and cutter grinders enhance productivity by typically offering features such as automatic tool loading as well as the ability to support multiple grinding wheels. High levels of automation, as well as automatic in-machine tool measurement and compensation, allow extended periods of unmanned production. With careful process configuration and appropriate tool support, tolerances less than 5 micrometres (0.0002") can be consistently achieved even on the most complex parts.

Apart from manufacturing, in-machine tool measurement using touch-probe or laser technology allows cutting tools to be reconditioned. During normal use, cutting edges either wear and/or chip. The geometric features of cutting tools can be automatically measured within the CNC tool grinder and the tool ground to return cutting surfaces to optimal condition.

Significant software advancements have allowed CNC tool and cutter grinders to be utilized in a wide range of industries. Advanced CNC grinders feature sophisticated software that allows geometrically complex parts to be designed either parametrically or by using third party CAD/CAM software. 3D simulation of the entire grinding process and the finished part is possible as well as detection of any potential mechanical collisions and calculation of production time. Such features allow parts to be designed and verified, as well as the production process optimized, entirely within the software environment.

Tool and cutter grinders can be adapted to manufacturing precision machine components. The machine, when used for these purposes more likely would be called a CNC Grinding System.

CNC Grinding Systems are widely used to produce parts for aerospace, medical, automotive, and other industries. Extremely hard and exotic materials are generally no problem for today's grinding systems and the multi-axis machines are capable of generating quite complex geometries.

Radius grinder

A radius grinder (or radius tool grinder) is a special grinder used for grinding the most complex tool forms, and is the historical predecessor to the CNC tool and cutter grinder. Like the CNC grinder, it may be used for other tasks where grinding spherical surfaces is necessary. The tool itself consists of three parts: The grinder head, work table, and holding fixture. The grinder head has three degrees of freedom. Vertical movement, movement into the workpeice, and tilt. These are generally set statically, and left fixed throughout operations. The work table is a T-slotted X-axis table mounted on top of a radial fixture. Mounting the X axis on top of the radius table, as opposed to the other way around, allows for complex and accurate radius grinds. The holding fixtures can be anything one can mount on a slotted table, but most commonly used is a collet or chuck fixture that indexes and has a separate Y movement to allow accurate depth setting and endmill sharpening. The dressers used on these grinders are usually quite expensive, and can dress the grinding wheel itself with a particular radius.

D-bit grinder

D bit grinder

The D-bit grinder is a tool bit grinder that specializes in the grinding of D-bit cutters for pantograph milling machines. Pantographs are a variety of milling machine used to create cavities for the dies used in the molding process, they are being rapidly replaced by CNC machining centers.

Basic Mechanisms Of Tool Wear

The various mechanisms that contribute to wear process are as below .

• Mechanical overload causing micro breakages (attrition). 

• Abrasion
• Adhesion
• Diffusion

Attrition :
The grains of the various components of the tool material hold together at grain boundaries. Those on the rake face and on the flank are supported on at least half of their surfaces and can therefore be rather easily broken out, embedded in the machined surface and in the underside of the chip, and dragged over the tool surface. Some of them may then break out other grains and produce a kind of chain effect.
 

Abrasion :
Abrasion is the commonly known wear process in which a harder material scratches a softer material over which it is sliding under normal pressure. This mechanism is significant for tool wear only in those instances where the workpiece material is very hard or contains hard particles: cast iron with grains of cementite, various metal containing hard inclusions like hypereutectic aluminum with SiC grains, steel killed with aluminum and containing Al2O3 , and so on. The machined surface is cooler than the tool flank, and it may happen that tool material is softened more than some of the constituents of the workpiece materials, which creates the conditions for abrasion.
 

Adhesion :
In the conditions of the intimate contact between the tool and the freshly created surfaces on the workpiece and on the underside of the chip, welding of the workpiece surface and of the chip to the tool can often be observed. The extreme case is the built-up edge, which is formed in the low and middle speed range. Layers of workpiece material welded to the tool are found in ductile materials like in ferritic and Tehran International Congress on Manufacturing Engineering  Tehran, Iran austenitic steels, titanium alloy, and nickel-based alloys. The welded layers and points are periodically sheared away. This mechanism contributes to flank wear as well as to the formation of the crater.
 

Diffusion:
Diffusion is an important mechanism and plays a significant role at higher cutting speeds in some workpiece/tool material combinations. The diffusion rate, that is, the amount of atoms of material penetrating into another material, depends on the affinity of the two, very strongly on temperature, and on the gradient of concentration of the penetrating atoms in the solvent material. The latter aspect is very special in cutting, because the chip materials that absorbs the atoms of the tool material is continuously being carried away, and all the time new, virgin, unsaturated material is always arriving.

Orthogonal and Oblique Cutting

Orthogonal Cutting: 

The cutting condition when chip is expected to flow along the orthogonal plane is known as orthogonal cutting.pure orthogonal cutting is orthogonal cutting when principle cutting angle is 90 degree.

Oblique Cutting:

 When the chip does not flow on orthogonal plane i.e chip deviates from orthogonal plane then it is called oblique cutting.

Basic Difference Between Orthogonal and Oblique Cutting: 

 In oblique cutting inclination angle(lamda) have some value but in orthogonal cutting there is no lamda i.e lamda=zero.

Causes of orthogonal cutting:

• Restricted cutting effect.
• tool nose radius-ing.
• inclination angle (Lamda not equal to zero).

Cutting Processes

Cutting processes work by causing fracture of the material that is processed. Usually, the portion that is fractured away is in small sized pieces, called chips. Common cutting processes include sawing, shaping (or planing), broaching, drilling, grinding, turning and milling. 

Although the actual machines, tools and processes for cutting look very different from each other, the basic mechanism for causing the fracture can be understood by just a simple model called for orthogonal cutting. In all machining processes, the workpiece is a shape that can entirely cover the final part shape. The objective is to cut away the excess material and obtain the final part. This cutting usually requires to be completed in several steps – in each step, the part is held in a fixture, and the exposed portion can be accessed by the tool to machine in that portion. 

Common fixtures include vise, clamps, 3-jaw or 4-jaw chucks, etc. Each position of holding the part is called a setup. One or more cutting operations may be performed, using one or more cutting tools, in each setup. To switch from one setup to the next, we must release the part from the previous fixture, change the fixture on the machine, clamp the part in the new position on the new fixture, set the coordinates of the machine tool with respect to the new location of the part, and finally start the machining operations for this setup. Therefore, setup changes are time-consuming and expensive, and so we should try to do the entire cutting process in a minimum number of setups; the task of determining the sequence of the individual operations, grouping them into (a minimum number of) setups, and determination of the fixture used for each setup, is called process planning

TOOLCHIP INTERFACE TEMPERATURE IN TURNING PROCESS

The cutting temperature is a key factor which directly affects cutting tool wear, workpiece surface integrity and machining precision according to the relative motion between the tool and workpiece. The amount of heat generated varies with the type of material being machined, cutting parameters, contact length between tool and chip, cutting forces and friction between tool and workpiece material. 

The temperatures which are of major interests are: average shear zone temperature, average (and maximum) temperature at the chip-tool interface, temperature at the work-tool interface (tool flanks), average cutting temperature. Temperature on the chip-tool interface is important parameters in the analysis and control of machining process. Total tool wear rate and crater wear on the rake face are strongly influenced by the temperature at chip-tool interface. Much research has been undertaken into measuring the temperatures generated during cutting operations.

To measure the tool temperature at the tool chip interface many experimental methods have been developed. The main techniques used to evaluate the cutting temperature during machining are tool-work thermocouple, embedded thermocouple and thermal radiation method. Design and develop control system to control the temperature lead to decrease tool wear and better surface finish. Production research activities in a real production environment supported by statistical experimental procedures enable continuous improvement of control processes and further cost .

Milling Cutter Nomenclature

As far as metal cutting action is concerned, the pertinent angles on the tooth are those that define the configuration of the cutting edge, the orientation of the tooth face, and the relief to prevent rubbing on the land.

Outside diameter — The diameter of a circle passing through the peripheral cutting edges. It is the dimension used in conjunction with the spindle speed to find the cutting speed (SFPM).

Root diameter — This diameter is measured on a circle passing through the bottom of the fillets of the teeth.

Tooth — The tooth is the part of the cutter starting at the body and ending with the peripheral cutting edge. Replaceable teeth are called inserts.

Tooth face — The tooth face is the surface between the fillet and the cutting edge, where the chip slides during its formation.

Land — The area behind the cutting edge on the tooth that is relieved to avoid interference is called the land.

Flute — The flute is the space provided for chip flow between the teeth.

Gash angle — The gash angle is measured between the tooth face and the back of the tooth immediately ahead.

Fillet — The fillet is the radius at the bottom of the flute, provided to allow chip flow and chip curling.

The terms defined above apply primarily to milling cutters, particularly to plain milling cutters. In defining the configuration of the teeth on the cutter, the following terms are important.

Peripheral cutting edge — The cutting edge aligned principally in the direction of the cutter axis is called the peripheral cutting edge. In peripheral milling, it is this edge that removes the metal.

Face cutting edge — The face cutting edge is the metal removing edge aligned primarily in a radial direction. In side milling and face milling, this edge actually forms the new surface, although the peripheral cutting edge may still be removing most of the metal. It corresponds to the end cutting edge on single point tools.

Relief angle — This angle is measured between the land and a tangent to the cutting edge at the periphery.

Clearance angle — Is provided to make room for chips, thus forming the flute.

Radial rake angle — The angle between the tooth face and a cutter radius, measured in a plane normal to the cutter axis.

Axial rake angle — Measured between the peripheral cutting edge and the axis of the cutter, when looking radially at the point of intersection.

Blade setting angle — When a slot is provided in the cutter body for a blade, the angle between the base of the slot and the cutter axis is called the blade setting angle.