There are various types of tools which are used with CNC machines. These tools are differentiated by their method of material removal. Generally there are classified as below,
- END MILLS:
- Flat nose mills are used for milling 2D contours and pockets. Ball nose mills are used for 3D milling. Bull noseend mills have a radius corner. They are used to create a fillet on the bottom of a wall. Because they are sturdier than an end mill they are also sometimes used for roughing operations. Chamfer mills have an angled nose used to create a chamfer or to de-burr parts.
|Types Of End Mills|
- Centre Cutting End Mills : Machine tools are generally centre cutting or non centre cutting. The advantage with centre cutting tools is that they can plung directly into the work-piece where as non centre cutting end mills cannot. In case of centre cutting end mills the flutes of cutting tool are extended upto the centre of the tool as shown in figure below but in non centre cutting end mills the flutes advances to a centre hole.
|Centre Cutting & Non Center Cutting End Mills|
- No of Flutes: Milling tools usually have either two or four cutting flutes. Two flute cutters provide more chip clearance when milling in close areas. Four flute mills are more rigid, can be fed faster, and are preferred when greater chip clearance is not required, such as when milling an outside contour.
2. FACE MILLS:
- The face mills consists of "cutting inserts" which can be replaced when worn out. These cutting inserts are mounted on a central boss. There are used for first roughing operation so as to produce a smooth surface for following machining operations. These may have upto 8 or more cutting edges (inserts) hence making material removal process fast.
3. SLOT MILLS:
- These types of cutters are used to cutting T-slots or dowtail type of shapes. T slots are very popular in case of machine beds for mounting fixtures or die etc.
|Slot Cutiing Mills|
4. HOLE MAKING TOOLS:
- SPOT / CENTER DRILL - These are used for creating a conic spot on the face of the workpiece so as to facilitate easy entrance of the twist dill at that point. The are short and rigid and provide precise location for a hole. The conic section created by the spot drill avoids wobbling and eccentric rotation of twist drills.
- COUNTERSINK DRILLS - These drills are used to create countersink type of hole profile so as to accommodate countersink screws. Drills having both spot drilling and countersink profiles are also available so as to carry out both operations by using single tool.
- TWIST DRILLS - These comes in various standard sizes according to metric and English standards. Used for drilling standard holes for various purposes. These are made up of High Speed Steel (HSS), carbide or Titanium Nitride (TiN) coated for long life and strength.
|Twist Drill Terms|
- TAPS & REAMERS - Taps are used to create threads in a pre-drilled hole. These form the materials by shearing away unwanted material. Taps require a hole drilled to the correct size to ensure the thread is formed properly. Most CNC Machines support rigid tapping, which means the tap can be held in a rigid holder. The tap is advanced at a feed rate that matches the thread lead into the hole. The spindle then stops, reverses, and backs out of the hole. Reamers are used to make hole bore of a precise size and excellent surface finish. Reamers give precise holes within 0.0001 mm.
Images Courtesy : CNC Handbook HSMWorks