How To Draw A Keyway In Autocad

Chapter vii

Keys, Cotter Joints, Pivot Joints

Affiliate Outline

Central Joints

Key

Cotter Joint

Example of Orthographic Project Drawing Using AutoCAD

Key, cotter, and pin are employed as temporary fasteners to join two components to transmit motion and forces from one chemical element to another. Maybe the most common of these movement-transmitting connections are keys. Keys are usually driven parallel to the centrality of the shaft that are subjected to torsional movement. Cotters are normally driven at right angles to the axes of the connected parts.

Cardinal JOINTS

The major function of keys is to prevent relative rotation between the members connected by keys and keyways, for instance, motor shaft and pully, gears, couplings crank, crankshaft then on. In addition to relative rotational move, keys as well prevent relative axial movement. The extensive use of fundamental joints is largely due to their simple still robust design, convenience of assembly and disassembly, low cost, and so on.

Key

Key is commonly a rectangular or slightly tapered piece with a square, rectangular, or round department—Fig. 7.1a. Keys are commonly made of cold finished low-carbon steel, though heat treated blend steels are also used when keys are subjected to considerable burdensome and shearing load. Fig. seven.1b illustrates the application of a round key (pin) to connect two components.

FIG. 7.i Awarding of round key

A key should be designed in such a style that information technology becomes the weakest component of the assembly and thus acts as a mechanical fuse. In order to adapt the central, a seat or groove is cutting in the shaft besides every bit on the hub (keyway) as shown in Fig. seven.2. The groove on the shaft makes its effective cross-sectional area smaller, in add-on to the development of stress-concentration at the precipitous corners. This may often cause failure of the shaft or axle. The figure shows a rectangular cantankerous-section of a key without whatsoever tapering. If a taper key is employed, then the keyway depth (d) will not be compatible along its length to adjust the increase in thickness (t) of the fundamental due to tapering.

FIG. 7.2 Fundamental and keyway

A big number of standard keys discover use in engineering application. The choice of a particular central depends on the load to be transmitted. Keys tin can be broadly classified into the following catagories.

Sunk key It is a blazon of key which goes partly in the key seat, machined in the shaft, and partly in the central manner, machined in the hub. The majority of the keys vest to this category amid which rectangular and square sunk keys are commonly used in industry. Fig. 7.2 shows the arrangement of a rectangular sunk cardinal with parallel sides. The cross-department of a foursquare primal (not shown) is d/four × d/4 where d is the diameter of the shaft.

A sunk taper key is used for large power transmission, having either a rectangular or a square cross-department. The depth of the keyway is compatible inside the shaft but there is a tapering in the hub equally shown in Fig. seven.three. The estimate proportion at the thicker terminate of a sunk taper primal may exist taken as width W = 0.25d and thickness, T = 0.66W, for a rectangular cardinal and West = 0.25d and T = West, for a square key where d denotes the diameter of the shaft.

FIG. vii.3 Sunk taper key

Saddle key A saddle key may be of ii types. A flat saddle key–Fig. seven.4a—used for light duty only, is a rectangular piece with a taper of 1 : 100. It is inserted within the keyway made on the hub. No key seat or groove is cut in the shaft.

A hollow saddle key—Fig. 7.4b—is similar to a flat saddle cardinal and suitable for the same kind of work. A concave surface is made at the bottom of the key with a radius slightly less than that of the shaft. The proportion of the primal in terms of the shaft diameter d can be given every bit follows.

Width of the key Due west = 0.25d + 2 mm

Thickness of the cardinal T = 0.8d + one mm

FIG. 7.4 Saddle keys

FIG. 7.5 Woodruff key

FIG. 7.half-dozen Tangential key

Woodruff key It is extensively used in the motorcar manufacture and machine tools manufacture where low ability needs to be transmitted. Information technology has the course of a segment of a circular disc with uniform thickness. The curve portion is placed within the seat cutting in the shaft while the flat portion goes into the hub equally shown in Fig. vii.v. The disadvantage of this fundamental is that the shaft becomes weaker due to removal of material to make room for the keyseat. Various dimensions of the key in terms of shaft diameter (d) are mentioned in the figure.

Tangential primal or kennedy cardinal It is used for high power transmission equally in the case of rolling mills. The keys are tapered and driven tightly. To lock shafts subjected to reversal of management, two keys are placed 90° or 120° apart as shown in Fig. 7.vi.

Gib headed key It is an ordinary, regular primal with a gib at ane end so that it can be easily withdrawn with the help of a wedge between the gib and the hub at the space marked X in Fig. 7.vii The proportion of the gib head in terms of the shaft bore is also mentioned in the figure.

FIG. seven.7 Fundamental with gib head

Plume key A feather primal is similar to a parallel sunk key secured to the shaft by means of a cap screw as shown in Fig. 7.8c. The hub is free to slide axially though relative rotational motion betwixt the hub and the shaft is not possible. The cantankerous-section of a plumage key may be rectangular (Fig. 7.8a), square, or dove tail (Fig. seven.8b). Easier sliding is obtained with 2 keys spaced 180° apart. The ends of a feather primal are sometimes rounded (Fig. 7.ix).

FIG. 7.8 Feather fundamental

Splines Splines are multiple feather keys with the keys machined integral with the shaft (Fig. 7.10a). They are used primarily, when a single fundamental is not skilful enough to withstand the stress. The spline may exist of anfractuous shape or straight sided. It is mainly used in gear boxes of automobiles and motorcar tools where sliding or axial movement between the mating pieces are essential from a functional point of view. The keyways are provided on the sliding part (Fig. 7.10b). Both parts are developed using the AutoCAD solid modelling features.

FIG. 7.ix Feather key (solid model)

FIG. 7.10 Spline shaft (solid model)

COTTER JOINT

A cotter (Fig. seven.11a) is a flat key-like component with a rectangular cross-section of compatible thickness but tapering to one side in general. This tin can be very efficiently used to connect two rods subjected to axial load either compressive or tensile in nature. The cotter is inserted perpendicular to the axes of the rods. Fig. 7.11b clearly illustrates the arrangement of a cotter articulation in parametric view. It should be noted that a cotter joint cannot transmit rotary motion from i shaft to some other.

FIG. 7.11 Cotter joint

The joints are simple in pattern and allow a convenient and quick assembly and disassembly. The primary shortcomings of a cotter joint are that it is difficult to industry and that a locking arrangement for the cotter is necessary for important cases.

The taper in a cotter is more often than not 1 in xxx. If for some reason, a larger taper is provided, a locking organisation is made so that the cotter does not come out or get loose. If the diameter of the rod is given by d, and then the other proportions of the cotter are as follows.

Width of the cotter at the center, W = 1.3d

Thickness of the cotter, T = 0. 31 d

There are some variations of cotter joint to suit unlike purposes. Two of them are discussed beneath with figures.

Socket and Spigot joint Here, one end of the rod is formed into a socket that fits into the other and having a larger diameter called a spigot. Both the ends are formed past forging. The dimensions of both the ends are made such that the socket tin can slide easily within the spigot. A slot, to conform the cotter, is provided in the socket and the spigot. The position of the slots are so adjusted that the cotter can be driven through them.

There is a clearance betwixt the cotter and the slots. Merely the cotter comes in contact with 2 rod ends on opposite sides then every bit to leave clearance on both sides. In fact, the clearance is very essential for the proper functioning of the cotter. Since a cotter either pulls or pushes (depending on the nature of the load) the slots forth the centrality, it makes the articulation perfectly tight and rigid. The orthographic project views of a typical socket and spigot cotter joint with all dimensions are shown in Fig. vii.12.

FIG. vii.12 Socket and Spigot joint

Sleeve articulation Sometimes, instead of making a spigot and a socket on each end of the rod, a split sleeve or muff fits over the end of each rod as shown in Fig. seven.xiii. This facilitates the manufacturing of the joint every bit both the rod ends are round in section. The position of the clearances should be noted as they are important to ensure a tight joint.

The detailed steps for the drawing of this joint in AutoCAD is described at the terminate of this chapter.

FIG. seven.xiii Cotter joint with sleeve

Gib and Cotter joint This type of joint is generally used to connect shafts with square rod ends equally shown in Fig. 7.14. One cease of the rod is converted into a fork or strap in which the rod end fits. Rectangular slots are provided at both ends to adapt the gib and cotter, keeping space for clearances in rod ends. The depth and the width of the gib heads are usually equal. The outer sides of the gib and the cotter are made parallel while the inner mating sides accept matching taper every bit shown in Fig. 7.14a. The orthographic one-half-section view of the gib and cotter joint is shown in Fig. vii.14b.

Pivot articulation or knuckle joint This joint is used to connect 2 rods whose axes intersect at a point and are subjected to tensile or compressive load. The joint is not rigid equally it allows modest relative angular movement between the rods. Unlike components of a knuckle joint along with their assembly view (Fig. seven.17) are developed in AutoCAD solid models and are presented here. The operational principle of the joint can be understood from these figures.

FIG. 7.14 Gib and Cotter joint

A pin joint is necessary to convert reciprocating motility into rotary equally in the case of a slider crank mechanism. Application of this articulation is found in valve and eccentric rods, lever and pump rod joint, tie rod joint for roof truss and so on. The pin is kept in position by ways of a collar and a taper pivot. Fig. 7.15 shows the orthographic views of the knuckle joint with all the dimensions.

FIG. vii.15 Pin-joint or knuckle joint

FIG. 7.16 Assembled view of a knuckle joint

FIG. 7.17 Exploded view of a knuckle joint

Example OF ORTHOGRAPHIC Project DRAWING USING AutoCAD

Cotter Joint with Sleeve

Now that y'all are familiar with AutoCAD cartoon commands required for two-D drafting, let us make an endeavor to develop an orthographic drawing of a cotter joint with sleeve starting from scratch. Since the object is complicated and symmetric, the inherent advantages of AutoCAD over the manual mode of drafting will exist appreciated more than by the readers.

The detailed working principle of the articulation is already mentioned earlier in this chapter. Here, nosotros shall concentrate only on the cartoon part. The dimensions of unlike components of the joint are shown in Fig. 7.18. Our objective is to reproduce the drawing shown in Fig. 7.18 using AutoCAD cartoon commands.

The detailed process of preparing the complete orthographic views is illustrated in the following steps. It is advisable to follow the same procedure for any drafting work with AutoCAD.

Step 1 Gear up upward the units of measurement and cull from the Metric or English options when y'all open a new drawing file. For this example, the option will exist Metric.

Stride two Adjacent set the Limits of your drawing area. This volition depend upon the basic dimensions of the object and the number of projection views to be represented. You lot may take to set aside some infinite for a clear margin all effectually the cartoon and also infinite for the title block, parts listing then on. Based on the dimensions of unlike components of the joint mentioned in Fig. 7.eighteen, the two corner points are called such that the entire cartoon can be accommodated in full scale (1:1). For the present case, the following limits are provided.

Limits: Lower left corner 0, 0

Upper right corner 450, 300

FIG. seven.eighteen Dimensions of dissimilar components of knuckle joint

Pace 3 Y'all should create suitable layers then that the outline of the object, center lines, hidden lines, dimensions, text objects, borders, and and so on tin can exist drawn on split layers. Each layer should have different linetypes with specified thicknesses (and colors, if applicable). For beginners, it may be advisable to create one layer for construction lines (Geometry) which may be turned off in the final drawing. Using the layer control, create the layers shown in Table 7.1.

Table 7.1 Different Layers Created for the Example

Name	Linetypes	Line Thickness
Object outline	Solid line	0.fifty mm
(Ooline)
Eye line	Heart	0.25 mm
(Center)		(Default)
Hidden	ISO dash	0.25 mm
(Hidden)		(Default)
Hatch	Solid line	0.25 mm
(Hatch)		(Default)
Dimension	Solid line	0.25 mm
(Dim)		(Default)
Text	Solid line	0.25 mm
(Text)		(Default)
Construction	Solid line	0.25 mm
		(Default)
Border	Solid line	0.35 mm

Step iv First of all, it is recommended to describe a rectangle (in structure layer) with lower left and upper correct corners as 0, 0 and 450, 300 respectively, indicating the limits of the cartoon area. Then draw the border (in Edge layer) taking showtime distances every bit per the margins to be left. Next, decide on the allotment of space for the drawing expanse and title block. In Fig. 7.nineteen a rectangular border (ABCD) is drawn in the construction layer where different views are to be drawn. Standard title box space (185 mm × 65 mm) is as well located at the bottom right corner. The layout of the drawing is thus consummate.

FIG. 7.xix Layout of the drawing

Stride five The Title Cake is more often than not a standardised format. Information technology can exist drawn separately or it may exist kept set up every bit Wblock for insertion at the appropriate places (discussed in the Block section). Here, a specimen Title Block following BIS guidelines which may be drawn or inserted as shown in Fig. 7.20.

FIG. 7.xx Standard Title box

After placing the Championship block and turning off the construction layer, your drawing will resemble Fig. 7.21. Remember, the shape of or the text in the Title block can be changed by exploding it (created by Wblock command).

FIG. seven.21 The drawing layout with Championship box

Pace 6 The general principle for cartoon whatsoever auto chemical element may be listed equally given below.

Draw center lines in all the views. If the cylindrical role or a pigsty is viewed as a rectangle in a particular view, then draw but ane center line along its axis (Fig. 7.22). However, if information technology is seen every bit a circle, draw two center lines intersecting at right angles at its centre.
Develop details of all the views in the sequence equally mentioned below.
1. Circumvolve and arcs.
2. Straight lines generating the shape of the object.
3. Minor details.
4. If the object is symmetrical, equally in the present case, and so one half may be fatigued in the initial phase and the other one-half may be generated by mirroring the formerly drawn portion.
Wherever necessary, add exclusive lines (hatching).
Put up dimensions.
Insert necessary text.

Following the above principles, draw the center lines for the side and forepart view of the cotter and sleeves. The outlines of the object in the side view will be circles with specified diameters. Afterwards this step your drawing will resemble Fig. 7.22.

FIG. seven.22 Cartoon the eye lines

FIG. 7.23 Projection lines earlier trimming

Footstep 7 Since the front end view is symmetrical about an centrality, develop the shape of the right hand part of the sleeve, shaft, and cotter. The left hand part may be generated past mirroring the correct manus part. The projection lines may be drawn initially by structure lines and later the final object outline parts (afterwards trimming) may be converted into object lines in Ooline layers. The correct paw part should be drawn starting time because, if you notice, the front view is actually a symmetrical view and therefore draw half of the object outset and then use mirror command to go the other half. After drawing the right hand part partially, the drawing will resemble Fig. vii.23. For clarity, only the drawing of the object is given. Note that the taper side of the cotter has been fatigued by giving proper offset distances and and then connecting the upper left betoken with the right bottom point with a line. The 2 lines showing these extremities will be somewhen erased.

Footstep 8 At present utilise the Trim command to delete all the excess lengths of the projections so that only the outline of the object remains in the drawing (Fig. 7.24).

FIG. 7.24 Object outlines afterward trimming

Stride ix Now fillet all the ends (fillet radius = three.0) that require filleting. Too, draw the upper and lower curved parts of the cotter in the front view and consummate its projection to the side view. Too show the broken shaft past cartoon arcs at the extreme right end of the shaft. Your figure will at present wait like Fig. vii.25. Notation that the edge lines of the sleeve on the left have been removed to suit the hatching. At this phase, convert some object lines into hidden lines every bit shown in Fig. seven.25.

FIG. seven.25 The completed front view before mirroring

Pace x Apply the mirror control to create the left hand view of the shaft, sleeve, and cotter at one stroke. Next, put all the essential dimensions in the dimension (Dim) layer. Terminate your drawing by hatching (in Hatch layer) in the required zones. The shaft is provided with local section only. The final version of the completed drawing is equally shown in Fig. 7.26.

FIG. seven.26 The final view of the drawing

Explain, with sketches, the utilise of (i) flat saddle central (ii) sunk cardinal with gib head (iii) woodruff central and (4) feather cardinal.
Explain, with sketches, the organisation of attaching a feather primal with the shaft and the hub of a pulley or gear.
What is the difference between a key and a cotter? State the purpose for which each is used.
Explain the divergence between a cotter joint and a pin joint with sketches. Why is clearance provided in a cotter joint?
Draw the two views of a cotter joint for joining two xxx mm diameter rods. Mention the necessary dimensions in the drawing.
Ii rods of diameter 25 mm are to exist joined by an arrangement of a cotter joint with a sleeve. Depict 2 views in full scale.
Why is a gib used along with a cotter? Draw the arrangement of a gib and cotter joint with the gib and cotter to connect ii shafts having a square section of 40 mm on each side.
Depict the necessary views of a knuckle articulation to connect ii rods, each with 40 mm bore.
Draw the detailed views of a knuckle joint shown in Fig. 7.15.
Depict two views of a 6-spline shaft, taking the outside diameter as eighty mm.
Fig. vii.17 shows different components of a knuckle joint created in solid model. Develop the isometric views of the component using the isometric settings provided in AutoCAD.
Draw the isometric views of the components of the cotter joint with sleeve described in Question vi.
Develop the pictorial view of a gib and cotter joint.
Develop the isometric view of a cotter joint described in Question v.