Gears

   

Gears are machine elements, which are used for power transmission between shafts, separated by small distance. Irrespective of the type, each gear is provided with projections called teeth and intermediate depressions called tooth spaces. While two gears are meshing, the teeth of one gear enter the spaces of the other. Thus, the drive is positive and when one gear rotates, the other also rotates; transmitting power from one shaft to the other.

Gears are classified on the basis of the shape of the tooth profile and the relative position of the shafts between which, power transmission takes place. The pictorial views of some of the most commonly used gear trains, are shown in Fig.

NX UNIGRAPHICS TOOLBARS

friends this post will be useful to the new CAD designers who are at their beginning level.

the following is the list of tools used in unigraphics software.

download and read it . you will be amazed to note at all the tools available at your fingertips

Limits of Size (IQC 5 )

Limits of size are two extreme permissible sizes between which the actual size exists.
 
The maximum limit for a dimension is the largest permissible size, while the minimum limit
for a dimension is the smallest permissible size.

 The maximum or minimum sizes represented by tolerances are called the limits. The basic sizes deviation and tolerances for both shaft and hole are illustrated in Fig

 
                                     Basic size deviation and tolerances for both shaft and hole

SIZE ( IQC 4 )

It expresses the numerical value of a length in a particular unit on the part. The basic
size of a part is its nominal dimension from where all variations are generally made.

 It is determined by the part designer from its functional requirements to meet the specified
objective. The other term used with respect to a part is the nominal size.

 The nominal size is the size of the part specified in the drawing as a matter of convenience. It is used primarily for the purpose of identification of a component and is never used in the precision measurement of parts. 

 A rigid attitude towards the maintenance of a basic size of the part may increase the
manufacturing cost and a little variation in dimension is accepted resulting in a size, which
is different from the basic size of the part. This is called the actual size.

 The actual size of a dimension or part is its measured size. An actual size of a ready part will, therefore, always deviate from one specified in the drawing, i.e. from the nominal or basic size of the part. Whereas the difference between the basic size and actual size must not exceed from a certain limit otherwise it will interfere with the interchangeability of mating components during assembly or sub assembly of parts.

INTERCHANGEABILITY ( IQC-3 )

The dimensions of mating parts are generally controlled to have a proper fitting of
matching parts for its optimal functional requirement. Providing dimensions on components
or parts is the job of a product designer.

 Interchangeability 

 of the parts is, therefore, a major pre-requisite for economic production, operation and maintenance of machinery mechanism and instruments. It is therefore very much possible to interchange spare parts in various machines, tractors, motor cars, machines tools, airplanes and many, others so that they can be dismantled for replacement of parts in service conditions in the field, and also in many local workshops with least possible loss of time.