Wednesday, 14 October 2015

Tool Bits


A Tool Bit is a type of non rotary cutting tool usually used with power tools like Milling machines and lathes also in shapers and planers. 


Since it is widely used in lathe lets review in short about the lathe and its operations.

Lathe : 

A Lathe is a machine tool used for shaping metal, wood and at times other pieces too. Lathe usually holds the workpiece and rotates it against the cutting material usually a tool bit to perform a cutting action. Lathe tool works on a principle of rotating work piece and a fixed cutting tool. Wood lathes were in use in France as early as 1569.
Below is the short description of the the various operations performed in lathe. 

Chamfering:

Chamfering is the beveling the extreme end of a workpiece and is a process done on finishing machined parts, usually making a cut at a 45 degree angle, to remove a 90 degree edge. A burr is a rough edge left on a workpiece after cutting, drilling. It is usually an unwanted piece of material and is removed with a deburring tool. Burrs are most commonly created after machining operations.

Threading: 

Thread cutting is one of the most important operations performed in a lathe. Pointed tool is fed linearly across the rotating workpiece at large feed rate, thus producing threads. External or male thread is a thread on the outside of a cylinder or cone. Internal or female thread is a thread on the inside of a hollow cylinder or bore.

Turning:

Turning is one of the most common of metal cutting operations. As showed in the above diagram, turning is used to reduce the diameter of the workpiece, usually to a specified dimension.

Facing:

Facing is removal of material from the flat end of a cylindrical part. It is often used to improve the finish of surfaces that have been cut.

Grooving: 

Grooving is the act of making grooves of reduced diameter in the workpiece often done on workpiece shoulders to ensure the correct fit for mating parts. In Face grooving operations the tool is fed axially rather than radially toward the end surface of the workpiece.

Drilling

  It creates a cutting hole in a workpiece. It is different from boring as boring can only enlarge the existing holes. The tool used for drilling is called as drill or a drill bit.

Boring: 

Boring is the enlarging and truing of a hole by removing material from internal surfaces. Boring cannot originate a hole it can only enlarge a hole that has already been drilled. Counter Boring is enlarging a hole through a specific depth from the end instead of enlarging the whole drilled surface. On the other hand Countersinking is to enlarge and bevel the rim of a drilled hole. It allows the screw to sit flush with the surface of the material. Countersinking is done using a countersink drill bit.

Knurling:

Is a process where diamond shaped projections are formed on the workpeice, used for some types of screws and tool.

Magicut Tool Bits are made from the finest grades of steel imported from Western Europe and Japan. These are then tested in our well equipped laboratory for physical appearance, surface finishes, dimensions, grain size, chemical composition, other variables and defects before further processing - that includes a whole battery of tests, from checking of chemical composition to microscopic tests for carbide distribution. It is made sure that raw materials used meet with our requirements.

Heat-treatment is what transforms a soft, pliable piece of steel into hard, tough and wear resistant tool bit. This is the factor where there is no chance for compromise on quality. We have therefore opted for furnaces manufactured under German License to ensure precise automatic temperature control and of course very close process control. Even then each batch is carefully tested for micro-structure and each tool for hardness in well-equipped laboratory and quality control department. After well - controlled further processing what we have is tool bit to give you the best in every desired quality.


Below are the qualities available in Tool Bits. 

Magicut HSS M2 Tool Bits:

Made from High Speed Steel bearing tungsten- molybdenum grade for use on relatively soft material. They have good heat and abrasion resistant properties.

Magicut HSS M35 Tool Bits:

 Made from High Speed Steel bearing 5% Cobalt. It is an economical grade for general purpose use in workshop and is best suited for applications involving interrupted cuts and roughing operation. They have high heat and abrasion resistant properties and are best used when making heavy cuts, at high speeds.

Magicut HSS M42 Tool Bits: 

Have a high degree of hot hardness and wear-resistance. Made from High Speed Steel bearing 8% Cobalt, these offer top efficiency on difficult-to-machine alloys and high strength steels. They have increased water resistance and tool life.

HSS T - 42 Tool Bits: 

Have exceptional wear resistance property. Made of 10% Cobalt bearing High Speed Steel, these have high hot hardness, edge-holding ability in addition to ample toughness for all types of cutting tool applications including those at high temperatures and speeds. They are especially adopted for roughing or finishing operations where maximum tool life is required; for large- batch automatic lathe work and all types of lathe and boring operations.

Relative Properties of Magicut Grades: 

Depending on the nature of cutting operation like ease of cutting, hardness of job, machinability of the job, speed of cutting and heat generated at the cutting action the right grade of tool is to be selected. The relative hot hardness, wear resistance and toughness of various grades are indicated in the chart.


Correct Grinding:
 
The heat generated while grinding the cutting edges reduces the hardness at the cutting edges, thereby lowering the cutting efficiency of a sharpened tool. Therefore, when grinding tool bits:

- Use a soft wheel, appropriately dressed.
- Apply light pressure and constantly rotate the tool bit surface to avoid discoloration or burning of the cutting edge.
- Avoid sudden change of temperature DO NOT dip the hot tool in cold water (otherwise the tool will develop surface cracks, which reduce the tool efficiency and life).
- Hand stoning of the finish ground faces lengthens life between regrinds and enhances surface finish achieved with finishing cuts.

Correct Form:
  
 To get high cutting efficiency it is vital that correct tool geometry (profile) is maintained when regrinding the tool. Correct grinding of various angles of a tool can greatly improve the tool bit's performance. Please refer to the Magicut chart for details of correct angles for cutting different materials.

 
Recommended tool Geometry:



Tool Bits should be fitted in the tool post or tool holder with a minimum of overhang as shown below (in the ratio of 1:1 of the tool size or less). The base of the tool bit should be flush with the tool post. When shims are used they should cover the entire length of the tool bit that rests on the tool post.It is not advisable to use a bent shim. Tool bits can break at section XX as shown in figures 1, 2 & 3.

HSS Square Tool Bits:



Magicut Square Tool Bits are available in M2, M35 (5% Cobalt), T42 ( 10% Cobalt), T42 ( 10% Co CRYO) grades.

Rectangular/Flat Tool Bits:

 


Magicut Rectangular or Flat tool bits are available in M2 grade.

Parting tools:

Parting Tool is a type of cutting tool inserted directly into the workpiece to cut off the workpiece at a specific length. It is  used to remove the finished end of a workpiece that is attached to the chuck. Parting tools are tools that are generally thin blades of HSS.

 





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