Engine Bearing | Structure of Engine Bearing

Engine bearing

         The crankshaft if supported by bearing. The connecting rod big end is joined to be crank pin on the crank of the crankshaft through a bearing. A piston pin at the rod small end is accustomed attaching the rod to the piston. The piston pin drives in bearings. Everywhere there is rotating action in the engine, bearings are accustomed supporting the moving parts. The presence of bearing is to decrease the friction and to allow the parts to move easily. Bearings are lubricated with oil to make the relative motion easier.Bearings used in engines are of two types : sliding or rolling

01 - Bearings present in engine - types of bearings

            The sliding type of bearings are sometimes called bushings or sleeve bearings because they are in the shape of sleeve that fits around the rotating journal or shaft. The sleeve-type connecting rod big end bearings usually called simply rod bearings and the crankshaft supporting bearings called the main bearings are of the split sleeve type.

01 - engine bearings - types of bearings

         They must be split in order to permit their assembly into the engine. the upper half of the rod bearing is fitted in the rod, the lower half is mounted in the rod bearing cap. When the rod cap is fastened to the rod shown in the picture complete sleeve bearing is formed. Likewise, the upper halves of the main bearings are assembled in the engine and then the main bearing caps, with the lower bearing halves are attached to the engine to complete the sleeve bearings supporting the crankshaft.

Structure of a bearing

        The typical bearing half is made of steel or bronze back to which a lining of relatively soft bearing material is applied. This relatively soft bearing material, which is made of several materials such as copper, lead, tin and other metals, has the ability to conform to slight irregularities of the shaft rotating against it. If wear does take place, it is the bearing that wears and the bearing can be replaced instead of much more expansive crankshaft or other engine part.

01 - bearing structure - structure of engine bearing

              The rolling-type bearing uses balls or rollers between the stationary support and the rotating shaft. Since the balls or rollers provide rolling contact, the frictional resistance to movement is much less. In some roller bearings, the rollers are so small that they are hardly bigger than needles. These bearings are called needle bearings. Also some rollers bearings have the rollers set at an angle to the races, the rollers roll in are tapered. These bearings are called tapered roller bearings. Some ball and roller bearings are sealed with their lubricant already in place. Such bearings require no other lubrication. Other do require lubrication from the oil in the gasoline or from the engine lubrication system.

        The type of bearing selected by the designers of the engine depends on the design of the engine and the use to which the engine will be put. Generally sleeve bearings, being less expensive and satisfactory for most engine application. Infact sleeve bearings are used almost universally in all automobile engines. But you will find some engine with ball and roller bearings to support the crankshaft and for the connecting rod and piston-pin bearings.

Milling Operations | Functions Performed By a Milling Machine

Milling Machine

         Milling is the process of removing metal by feeding the work past against a rotating multipoint cutter. The metal is removed in the form of small chips. In milling operation the ratio of metal removal is rapid as the cutter rotates at a high speed and has many cutting edges thus the jobs are machined at a faster rate than with single point tools and the surface finish us also better due to multi cutting edges. It is used for machining flat and irregular surface.


Milling operation

1. Plain or slab milling

01 - plain mill cutter - milling operation

Plain milling is the operation of producing flat horizontal surface parallel to the axis of the cutter using a plain milling cutter.

2. Face milling

01 - face milling -types of milling

The method of producing flat surface on the which is at the right angle to the axis of rotation of the cutter is called as face milling.

3. Angular or bevel milling.


It is the operation of machining a flat surface at an angle other than the axis of the revolving cutter. The cutter used may be a single or double angle cutter depending upon whether a single surface is to be machined or two mutually inclined surfaces simultaneously.

4. Straddle milling


Straddle milling is the operation of producing two vertical flat surfaces on both sides of the job by using two side milling cutters which are separated by collars. Straddle milling is very commonly used for milling square and hexagonal surfaces.

5. Gang milling


Gang milling is the production of many surfaces of a job simultaneously by feeding the table against a number of required cutters. The two plain milling cutters have helical teeth of opposite hands. This method of operation saves machining time and hence it is widely used in mass production.

6. Form milling

Form milling is the operation of producing irregular surfaces or contours by using required form cutters. The irregular shape may be convex, concave or any other shape.

7. End milling

01 - end milling - types of milling

It is the operation of producing both peripheral and face milling operation simultaneously generates vertical, horizontal or angular surfaces by using a end milling cutter. It is used for milling slots, grooves, keyway etc.

8. T slot milling

Milling of t-slots is produced in two or three stages. In the first operation, the end milling operation or a plain slot is made by using an end milling cutter.


In the second operation. T-slot is made by using the t-slot cutter to enlarge the slot and to mill the bottom face of the slot.

9. Gear cutting

the gear cutting operation involves cutting of different types of gears on a milling machine.


It is performed by using a form relieved cutter which is having the profile corresponding to the required tooth shape of the gear. Equally spaced gear teeth are cut on a gear blank by holding the work on a universal dividing head and then indexing it.