Blueprint Forged Rocker. Section 5 Sections Unit 26 Cutting Planes, Full Sections,. Blueprint 26A: Idler Shaft Support. Assignment BPA. Blueprint 26B: Pump System Mount. Assignment BPB. Unit 27 Half Sections, Partial Sections, and.
Full Section Assembly Drawings. Blueprint 27A: Cone Clutch. Blueprint 27B: Adapter Bracket. Section 6 Computer Numerical Control. CNC Fundamentals Unit 28 Datums: Ordinate and Tabular. Blueprint Shifter End Plate.
Blueprint 34B: Tee Slide. Unit 35 Sketching Curved Lines and Circles. Blueprint 35A: Shaft. Blueprint 35B: Slide Block. Blueprint 35C: Flange. Assignment BPC. Unit 36 Sketching Irregular Shapes. Blueprint Tool Block. Unit 37 Sketching Fillets, Radii, Rounded. Corners, Edges, and Shading. Blueprint 37A: Drop Forged Strap. Blueprint 37B: Shaft Support. Section 7 Geometric Dimensioning. Unit 29 Geometric Dimensioning, Tolerancing,.
Blueprint Intake Shaft. Bearing Plate. Section 8 Computer Graphics Technology Blueprint Fixture Slide Block. Section 9 Speciality Drawings Unit 31 Welding Symbols, Representation,. Blueprint 31A: Welded Slide. Bearing Support.
Blueprint 31B: Welded Rotary Plug. Unit 32 Surface Development and. Precision Sheet Metal Drawing. Blueprint Circuit-Dial Cover. Section 10 Working Drawings Unit 33 Detail Drawings and Assembly. Blueprint 33A: Rotary Indexing. Sheet 1: Tiller Shaft. Sheet 2: Tiller Shaft. Sheet 3: 30 Tooth Cast Gear. Sheet 4: Button-Hard, Sheet 5: Remachining-Tiller. Section 11 Sketching Lines and. Basic Forms Unit 34 Sketching Horizontal, Vertical,.
Blueprint 34A: Punch Plate. Unit 19 Representing and Dimensioning. External Screw Threads. Blueprint Spindle Shaft. Unit 20 Representing and Specifying Internal. Blueprint Rocker Base.
Unit 21 Dimensioning Tapers and. Machined Surfaces. Blueprint Offset Carrier Arm. Unit 22 Dimensioning with Shop Notes. Blueprint Cutter Adapter. Section 12 Freehand Lettering Unit 38 Freehand Vertical Lettering.
Blueprint Straight Lettering. Unit 39 Freehand Inclined Lettering. Blueprint Slant Lettering. Section 13 Technical Sketching: Pictorial Drawings Unit 40 Orthographic Sketching.
Blueprint 40A: Rocker Fixture. Blueprint 40B: Guide Bracket. Unit 41 Oblique Sketching. Blueprint Pawl Reset Arm. Unit 42 Isometric Sketching. Blueprint Clutch Guide. Unit 43 Perspective Sketching.
Blueprint Turntable Unit. What is the overall height from the top of the brace to the bottom? What is the width of each leg of the brace? What is the thickness of the metal in the brace? What is the name given to the kind of line 6. What kind of lines are D and E? What kind of lines are F and G? Why are object lines made thicker than extension and dimension lines?
What kind of line is A? What kind of line is B? What kind of line is C? Determine the overall length of the plate from left edge to right edge. Note: R 5 Radius. Determine the overall height of the plate from top to bottom. Give the center distance between the two upper holes. Determine distance D. What kind of line is E? What kind of line is F? What radius forms the rounded corner of the plate.
Name the material specified for the corner plate. How many corner plates are required? Projection lines, Figure 5—1, are thin, unbroken lines projected from a point in one view to locate the same point in another view. Projection lines do not appear on finished drawings except where a part is complicated and it becomes necessary to show how certain details on a drawing are obtained. In addition to the six common types of lines, the alphabet of lines also includes other types, such as the cutting plane and viewing plane lines, break lines, and phantom lines.
These less frequently used lines, Figure 5—2, are found in more advanced drawings and will be described in greater detail as they are used in later drawings in this text. What is the name of the part? What is the blueprint number? What is the plate order number?
How many parts are to be made? Name the material specified for the part. Study the Feeder Plate, BP Locate and name each line from A to Z in the space provided for each in the table.
Tell how each line from A to L is identified. However, when the shape of the object changes, portions are cut away or relieved or complex machining or fabrication processes must be represented on a drawing, the one view may not be sufficient to describe the part accurately.
The number and selection of views is governed by the shape or complexity of the object. A view should not be drawn unless it makes a drawing easier to read or furnishes other information needed to describe the part clearly. Throughout this text, as the student is required to interpret more complex drawings, the basic principles underlying the use of all additional views that are needed to describe the true shape of the object will be covered. Immediate application of these principles will then be made on typical industrial blueprints.
The combination of front, top, and right-side views represents the method most commonly used by draftspersons to describe simple objects. The manner in which each view is obtained and the interpretation of each view is discussed in this section. The surface that is to be shown as the observer looks at the object is called the front view. To draw this view, the draftsperson goes through an imaginary process of raising the object to eye level and turning it so that only one side can be seen.
If an imaginary transparent plane is placed between the eye and the face of the object, parallel to the object, the image projected on the plane is the same as that formed in the eye of the observer, Figure 6—1. If, instead of converging, these rays are parallel as they leave the object, the image they form on the screen is equivalent to a front view, as shown in Figure 6—2. However, instead of looking squarely at the front of the object, the view is seen from a point directly above it, Figure 6—3.
When the horizontal plane on which the top view is projected is rotated so that it is in a vertical plane, as shown in Figure 6—4, the front and top views are in their proper relationship.
In other words, the top view is always placed immediately above and in line with the front view. That is, the draftsperson imagines the view of the object from the side that is to be drawn.
This person then proceeds to draw the object as it would appear if parallel rays were projected upon a vertical plane, Figure 6—5. Figure 6—6 shows the front, top, and right-side views in the positions they will occupy on a blueprint. The terms height, width, and depth refer to specific dimensions or part sizes. ASME designations for these dimensions are shown in Figure 6—7. Height is the vertical distance between two or more lines or surfaces part features that are in horizontal planes.
Width refers to the horizontal distance between surfaces in profile planes. Depth is the horizontal front to back distance between two features in frontal planes. Depth is often identified in the shop as the thickness of a part or feature.
These views show the exact shape and size of the object and define the relationship of one view to another. VIEWS 32 1. Name the material specified for the angle bracket. State the order number of the angle bracket. What is the overall width length of the angle bracket? What is the overall height? What is the overall depth? What is dimension A? What is dimension B? What surface in the top view is represented by line C in the right-side view?
Name the three views that are used to describe the shape and size of the part. What surface in the top view is represented by What line in the right-side view represents What line in the top view represents surface O in the right-side view?
What line in the front view represents surface H in the top view? What line in the right-side view represents surface H in the top view? What kinds of lines are A and B? What encircled letter denotes an extension line? What encircled letter in the front view denotes an object line? UNIT 6 1. How many angle brackets are required? Are the holes drilled all the way through the slide? What is the diameter of the holes? What line in the side view represents surface D in the top view? What line in the top view represents surface J in the front view?
What line in the front view represents surface D in the top view? What line in the front view represents surface Q in the right-side view? What line in the right-side view represents the slot shown in the front view? What two lines in the top view represent the slot shown in the front view? What do the lines marked A represent?
What are the lines marked A and B called? What is the overall height of the cross slide? What is the order number? UNIT 6 What kind of line is used at O and P? What kind of line is M? How high is the projection? What is the width of the projection at the top of the slide? Determine dimension S. What is the height of the slot?
What is the width of the slot shown in the front view? What is the overall width length of the cross slide? How far is the center of the first hole from the front surface of the side? How many pieces are required? What is the center-to-center dimension of the holes?
What material is used for the cross slide? Since the selection and arrangement of views depends on the complexity of a part, only those views should be drawn that help in the interpretation of the drawing. The average drawing that includes front, top, and side views is known as a three-view drawing. However, the designation of the views is not as important as the fact that the combination of views must give all the details of construction in the most understandable way.
The draftsperson usually selects as a front view of the object that view which best describes the general shape of the part. This front view may have no relationship to the actual front position of the part as it fits into a mechanism.
The names and positions of the different views that may be used to describe an object are illustrated in Figure 7—1. Note that the back view may be placed in any one of three locations.
The views that are easiest to read and, at the same time, furnish all the required information should be the views selected for the drawing. Front View F.
Right-Side View R. Left-Side View L. Bottom View Bot. Back or Rear View B. Auxiliary View Aux. Top View T. Then, identify and place the name of each view in the spaces provided in Figure 7—4 and Figure 7—5.
The two views usually include the front view and a right-side or left-side view, or a top or bottom view. Symmetrical SYMM means that features on both sides of a center line C L shown on a drawing are the same size and shape.
Objects are indicated by two equal-length short, dark, parallel lines. These lines are placed outside the drawing of the object on its center line C L , Figure 8—1 below and BP-8C, page In the front view, Figure 8—1, the center line runs through the axis of the part as a horizontal center line. If the plug is in a vertical position, the center line runs through the axis as a vertical center line. The second view of the two-view drawing contains a horizontal and a vertical center line intersecting at the center of the circles that make up the part in this view.
Combinations of views commonly used in industrial blueprints are shown in Figure 8—2. There are two main reasons why a draftsperson will show a primary view, also known as the front view.
Whatever the shape of the detail and regardless of the number or positions of views, the hidden detail is represented by a hidden edge or invisible edge line, Figure 8—3. Name line I. What kind of line is D? Name line J. What kind of line is K? What circle in the top view represents diameter L? Give the diameter of L. What is the smallest diameter of the shaft? What is the height length of the rectangular part of the shaft?
Is the end shaft SYMM? Give the overall height length of the shaft. State the material from which the shaft is to be machined. UNIT 8 1. Name the two views shown. Is this part SYMM? What material is used? Name the two views that are used to represent the flanged sleeve. Name the kind of line indicated by each of the following encircled letters.
What is the outside diameter of both flanges? What is the height thickness of each flange? What is the diameter of the center hole? Does the hole go all the way through the center of the sleeve? What is the diameter of the hidden circle? Determine the total or overall height of the flanged sleeve. Name the two views used to describe the part. Identify the kind of line indicated by each of the following encircled letters. What is the overall depth A? What is the overall length B?
How many holes are to be drilled? What is the thickness height of the plate? What is the distance between the center of one of the two upper holes and the center line of the cover plate? Give the center distance C of the two upper holes. What is the radius that forms the two upper rounds of the cover plate? What radius forms the lower part of the cover plate? What kind of line is drawn through the center of the cover plate?
How much stock is left between the edge of one of the upper holes and the outside of the piece? These drawings are often supplemented with notes, symbols, and written information, Figure 9—1B and Figure 9—3. They are normally used to describe the shape of cylindrical, coneshaped, rectangular, and other symmetrical parts. Leaders are used to relate a note to a particular feature, as in Figure 9—2. Thin, flat objects of uniform thickness are represented by one-view drawings.
The one-view drawing at A in Figure 9—1 represents a cylinder of a given length and diameter. The drawing at B represents a symmetrical flat part. A capital R always refers to a radius on a blueprint. Example: In Figure 9—3, the diameter of the two holes in the gasket is. These will also show the usage of abbreviations and symbols. The combination of the one view and the supplemental information indicates the millimeter sizes for the hexagon head, the body diameters and lengths, the dimensions of the square end, and the overall length.
A pictorial drawing, which normally would not be included, shows what the part looks like. Figure 9—3 is a typical one-view drawing of a gasket. Since the third dimension, such as thickness depth , can be given as a note, gaskets, shims, and the like may be represented on a drawing by one view. Another example of a one-view drawing where symbols and machining notes are used to supplement the dimensions is shown in Figure 9—4.
Name the view represented on BP-9A. What is the shape of the shoulder pin? How many outside diameters are shown? What is the largest diameter? What diameter is the smallest hole? What is the overall length of the pin?
How deep is the. What letters represent object lines? What kind of lines are B and D? What letter represents the center line? What does the center line indicate about the holes and outside diameters? State the order number of the part. What material is specified for the pins? Explain briefly why all information required to produce the part may be provided in one view.
Tell why the part is symmetrical with the vertical axis. Identify the: a Order Number 4. Indicate the following: 5. Weight a a The thickness and kind of material in the pump spacer. Calculate the weight of the stamped parts in the order. Identify the letter that relates to each of the following types of lines or function: 6. Specify the angular dimension between each of the three center lines for the three equally spaced holes on the pump spacer. Give the size of the square hole. Calculate the number of degrees center line A is from center line C.
Explain the meaning of the note E. Compute the radius to the center of the 1. Determine the following dimensions: a The body diameter of the pump spacer. UNIT 9 1. Name the type of drawing used to represent the pump spacer. UNIT 10 Auxiliary Views As long as all the surfaces of an object are parallel or at right angles to one another, they may be represented in one or more regular views, Figure10—1. The surfaces of such objects can be projected in their true sizes and shapes on either a horizontal or a vertical plane or on any combination of these planes.
Some objects have one or more surfaces that slant and are inclined away from either a horizontal or vertical plane. In this situation, the regular views will not show the true shape of the inclined surface, Figure 10—2.
If the true shape must be shown, the drawing must include an auxiliary view to represent the angular surface accurately. The auxiliary view is in addition to the regular views.
Figure 10—3 shows an auxiliary view in which only the inclined surface and other required details are included. In an auxiliary view, Copyright Cengage Learning. In Figure 10—3, the true size and shape of surface A is shown in the auxiliary view of the angular surface.
For example, the auxiliary view may be an auxiliary front, top, bottom, left-side, or right-side view. On drawings of complex parts involving compound angles, one auxiliary view may be developed from another auxiliary view. The first auxiliary view is called the primary view, and those views developed from it are called secondary auxiliary views. For the present, attention is focused on primary auxiliary views.
Rounded surfaces and circular holes, which are distorted and appear as ellipses in the regular views, will appear in their true shapes and sizes in an auxiliary view.
The draftsperson develops this view by projecting lines 1 , 2 , 3 , 4 , and 5 at right angles to surface A. When the front view is compared with the partial auxiliary view, it can be seen that the hole in surface A appears as an ellipse in the front view.
The height of surface A is foreshortened in the regular view, while the true shape and size are shown on the auxiliary view.
In Figure 10—3, the combination of left-side view, partial auxiliary top view, and front view, when properly dimensioned, shows all surfaces in their true size and shape. As a result, these are the only views required to describe this part completely. What is the center-to-center distance of the DIA. How many DIA. What surface in the front view is the same as 9. Determine dimension B. What is the distance between the face surface represented by line Q. Determine the vertical distance between the surface N in the top view?
What line in the front view represents surface 7. Give the diameter of hole F. Determine dimension A. What do K lines and R represent? J in the top view? What line in the front view represents surface What line in the top view represents surface H in the front view? G in the front view? What surface in the top view is represented by line E in the auxiliary view? What kind of line is P? Name each of the following: 3. III II 4. However, to construct or machine a part, the blueprint or drawing must include dimensions that indicate exact sizes and locations of surfaces, indentations, holes, and other details.
The lines and dimensions, in turn, are supplemented by notes that give additional information. This information includes the kind of material used, the degree of machining accuracy required, details regarding the assembly of parts, and any other data that the craftsperson needs to know to make and assemble the part. These standards are called the language of drafting and are in general use throughout North America.
While these drafting standards or practices may vary in some respects between industries, the principles are basically the same. The practices recommended by ASME for dimensioning and for making notes are generally followed in this section. Standards for Dimensioning All drawings should be dimensioned completely so that a minimum of computation is necessary and the parts can be built without scaling the drawing.
However, there should not be a duplication of dimensions unless such dimensions make the drawing clearer and easier to read. Many parts cannot be drawn full size because they are too large to fit a standard drawing sheet or computer screen or too small to have all details shown clearly.
The draftsperson can, however, still represent such objects either by reducing in the case of large objects or enlarging for small objects the size to which the drawing is made. This practice does not affect any dimensions, as the dimensions on a drawing give the actual sizes.
If a drawing 60 long represents a part long, a note should appear in the title box of the drawing to indicate the scale that is used. This scale is the ratio of the drawing size to the actual size of the object. In this case, the scale 60 5 is called half scale, or Other common scales include the one-quarter scale , one-eighth scale , and the double-size scale Dimensions may appear on drawings as twoplace decimals.
These are widely used when the range of dimensional accuracy of a part is between 0. Where possible, two-place decimal dimensions are given in even hundredths of an inch. Three- and four-place decimal dimensions continue to be used for more precise dimensions requiring machining accuracies in thousandths or ten-thousandths of an inch. In the case of a regular prism, two of the dimensions are usually placed on the principal view and the third dimension is placed on one of the other views, Figure 11—2.
These dimensions serve two purposes: 1 they indicate size, S , and 2 they give exact locations L. For example, to drill a through hole in a part, the technician must know the diameter of the hole and the exact location of the center of the hole, Figure 11—1. This technical information assists them in placing size and location dimensions, required for each operation, on the drawing.
Figure 11—3 shows how size and location dimensions are indicated. This practice is followed to overcome inaccuracies due to variations in measurement caused by surface irregularities.
Leaders used for dimensioning. The term leader refers to a thin, inclined straight line terminating in an arrowhead. The leader directs attention to a dimension or note and the arrowhead identifies the feature to which the dimension or note refers. A few sample leaders are given in Figure 11—5. If a series of dimensions is required, the dimensions should be placed in a line as continuous dimensions, Figure 11—7A.
This method is preferred over the staggering of dimensions, Figure 11—7B, because of ease in reading, appearance, and simplified dimensioning. UNIT 11 Continuous dimensioning is also called chain dimensioning, whereby each dimension is dependent on the previous dimension. Chain dimensioning is commonly used on architectural and construction drawings.
It is also used in computer-controlled applications requiring a high degree of dimensional accuracy. The common practice in placing dimensions is to keep them outside the outline of the object. The exception is where the drawing may be made clearer by inserting the dimensions within the object. When a dimension applies to two views, it should be placed between the two views, as shown in Figure 11—6.
In such instances, the dimension is placed on either side of the extension line or a leader is used, Figure 11—8 A, B, C, and D. Dots are also used on drawings for dimensioning when space is limited as shown in Figure 11—8E.
Place an X in the correct block to identify the kind of dimension to which each letter refers. Indicate one letter on the two-view drawing that identifies each of the following types of lines: 1. Give the dimensions in both views in the circles provided.
In the older almost obsolete method, called the aligned method, each dimension is placed in line with the dimension to which it refers, Figure 12—1A.
The second method, the unidirectional method recommended by ASME , has all numbers or values placed horizontally one direction , regardless of the direction of the dimension line.
All values are read from the bottom, Figure 12—1B. The aligned and unidirectional methods are illustrated in Figures 12—1A and Figure 12—1B on similar drawings of the same part.
Note at A that the aligned dimensions are read from both the bottom and the right-side. By contrast, the unidirectional dimensions, Figure 12—1B, are read from the bottom one direction only. This method of dimensioning is preferred because on small diameter cylinders and holes, a dimension placed in the hole is confusing. Many round parts, with cylindrical surfaces symmetrical about the axis, can be represented on one-view drawings.
The abbreviation for diameter, DIA, is used with the dimension in such instances because no other view is needed to show the shape of the surface, Figure 12—3A. In other words, when a cylinder is dimensioned, DIA should follow the dimension unless it is evident that the dimension refers to a diameter.
ASME standards require a radius dimension to be preceded by the letter symbol R, as shown in Figure 12—4. Many times, the center is not important, since the location of a radius arc is controlled by features or dimensions.
Dimensioning in such cases is simplified by conveniently placing the radius dimensions, as shown in Figure 12—5. Refer to the two-view drawing. Give one letter that identifies each type of line.
Name the two views. Determine the overall length of the Gear Arm. Give the overall length of the elongated slot. What is the outside diameter of the upright portion? Give the dimensions required in both views in the circles provided, by using the unidirectional method. The dimensioning at B shows the use of the ASME symbol to represent a counterbored hole and to indicate depth.
The counterbored hole provides a flat surface for the bolt or pin to seat against. The dimension line for an angle should be an arc whose ends terminate in arrowheads. The numeral indicating the degrees in the angle is read in a horizontal position, except where the angle is large enough to permit the numerals to be placed along the arc, Figure 13—5.
The symbol is used to indicated an arc. The amount of the divergence the amount the lines move away from each other is indicated by an angle measured in degrees or fractional parts of a degree. Two common methods of dimensioning angles show 1 linear dimensions or 2 the angular measurement, as illustrated in Figure 13—4. What does the line E in the front view represent?
What lines in the top view represent the dovetail? Name the kind of line shown at J. Name the kind of line shown at I. UNIT 13 5. What is the angle to the horizontal at which the dovetail is cut? How deep is the dovetail machined? How wide is the opening in the dovetail? What is the basic dimension C? Give the diameter of the B largest holes. What dimensions are given for the countersunk holes? Name the kind of line shown at G. Name the kind of line shown at H. Give the dimensions for the counterbored holes.
What is the outside diameter of the boss? How many bosses are shown on the uprights? Determine height A. How far off from the center of the support is the center of the two holes in the bosses of the uprights? Name the kind of line shown at E. This method of locating the center is preferred to making an angular measurement. In Figure 14—1, the center of the circle and arc may be easily found by measuring the vertical and horizontal center lines from the machined surfaces.
The size and position of each hole are noted on the drawing, Figure 14—3A. If more than one hole is the same diameter, then a notation may be used to indicate this fact, Figure 14—3B. Dimensions are usually given, in such cases, in the view that shows the shape of the holes; that is, square, round, or elongated.
The preferred method of placing these dimensions is shown in Figure 14—4A. Name the view that shows the width height of the coupling. Name the view in which the holes are shown as circles.
What circle represents the 4. What circle represents the 1. Name the kind of line shown at N. How many holes are to be drilled in the larger flange? Indicate the drill size to be used.
Give the diameter circle on which the equally spaced holes are drilled in the larger flange. How many holes are to be drilled in the smaller flange? How deep is the 1. Give the diameter of the reamed holes. What is the overall width height of the coupling? What is the diameter of the smaller flange?
UNIT 14 State the angle with the horizontal center line used for locating reamed hole O. What is the diameter of the circle A and B? What is the depth of the 1. What is the thickness of the larger flange? Determine distances C and D. C D Copyright Cengage Learning. This dimension line gives the size of the arc and indicates that the arc center lies on a center line outside the drawing. This technique is also used when a dimension line interferes with other parts of a drawing. Base line dimensioning is used when accurate layout work to precision limits is required.
Errors are not cumulative with this type of dimensioning because all measurements are taken from the base lines. Dimensions and measurements may be taken from one or more base lines. In Figure 15—2, the two base lines are at right angles to each other. The horizontal dimensions are measured from base line B , which is a machined edge. The vertical dimensions are measured from surface A , which is at a right angle to surface B and is also a machined surface.
An application of base line dimensioning, where a center line is used as the reference line, is shown in Figure 15—3A.
Base line dimensioning may also be applied to irregular shapes, such as the template shown in Figure 15—3B. UNIT 15 Base line dimensions simplify the reading of a drawing and also permit greater accuracy in making the part.
This applies primarily to manufacturing industries. By comparison, measurements for structural work and the building industry are usually given in feet and inches. What material is used for the base part? How many parts are required? What is the length of the base plate? What is the height of the base plate? What is the thickness depth of the base plate? How many. Give a the diameter and b the depth of counterbore for the.
What system of dimensioning is used on this drawing? Give the letter of the base line in the front view from which all depth dimensions are taken. Give the letter of the base line in the front view from which all horizontal dimensions are taken. Compute the following height dimensions: C , D , M , and F. Compute the following vertical dimensions: G , H , J , and K.
Compute dimensions N and O. Give the radius to which the corners are rounded. What is the radius of arc L? What letter indicates the center for arc L? Compute dimensions P and Q. P 5 Q 5 Copyright Cengage Learning.
UNIT 15 1. Each of these factors influences the degree of accuracy to which a part is machined. The dimensions given on a drawing are an indication of what the limits of accuracy are.
These limits are called tolerances. Parts may have a tolerance given in fractions or decimal inches or decimal millimeters. CAD drawings can dimension in any of these systems. For CNC-manufactured parts, decimal dimensions are required. The larger size is called the upper-limit; the smaller size is called the lower-limit. The degree may be divided into smaller units called minutes.
There are 60 minutes in each degree. Each minute may be divided into smaller units called seconds. There are 60 seconds in each minute.
To simplify the dimensioning of angles, symbols are used to indicate degrees, minutes, and seconds, Figure 16—2. Decimalized angles are now preferred. To convert angles given in whole degrees, minutes, and seconds, the following steps should be followed.
Convert minutes into degrees by dividing by 60 ing angles. Add whole degrees plus decimal degrees. The tolerance on an angular dimension may be given in a note on the drawing, as shown in Figure 16—3.
The tolerance may also be shown on the angular dimension itself, Figure 16—4. What letter is used to denote a a hidden edge line? Determine basic dimension G. What is the diameter of the drilled pilot hole for the counterbore? Give the diameter and depth heighth of the counterbore. Diameter 5. What are the upper- and lower-limits of tolerance for fractional dimensions? What limit of tolerance is specified for angular dimensions?
Give the upper-limit to which diameter B may be machined. Give the upper- and lower-limit on the diameter for shank F. Upper If shank F is machined to the upper-limit length height , how long will it be? Lower Copyright Cengage Learning. A dimension is said to have a unilateral single tolerance when the total tolerance is in one direction only, either 1 or 2. Bilateral tolerances applied to dimensions mean that the dimensions may vary from a larger size 1 to a smaller size 2 than the basic dimension nominal size.
In other words, the basic dimension may vary in both directions. The basic 2. These bilateral tolerances are shown in Figure 17—2.
When the dimensions within the tolerance limits appear on a drawing, they are expressed as a range from the smaller to the larger dimension, as indicated in Figure 17—2. In addition, the dimension can be measured with precision instruments to a high degree of accuracy and is required for Computer Numerical Control CNC applications.
Dimensions in the decimal system can be read quickly and accurately. Tolerances on decimal dimensions that are expressed in terms of two, three, four, or more decimal places may be given on a drawing in several ways. One of the common methods of specifying a tolerance that applies on all dimensions is to use a note, Figure 17—3.
The smaller size 1. A tolerance on a decimal dimension also may be included as part of the dimension, as shown in Figure 17—4. Bilateral tolerances are not always equal in both directions. It is common practice for a drawing to include either a 1 tolerance or a 2 tolerance that is greater than the other. In cases where the plus and minus tolerances are not the same, such as plus. The dimension above the line is the upper-limit; the dimension below the line is the lower-limit.
What is the vertical distance from line N to line S? What classification of tolerances applies to all dimensions? Change the decimal and angular tolerances so that only the 2 tolerances apply.
Then, determine the upper- and lower-limit dimensions for: 6. What is the maximum depth heighth to which the counterbored hole can be bored? What line in the top view represents surface R of the side view? What line in the front view represents surface L?
Compute dimensions V and X. Give the upper- and lower-limit dimensions for P. UNIT 17 What two lines in the top view indicate the opening of the dovetail? What dimension indicates how far line J is from the base of the slide? What is the full depth of the tee slot? What line in the side view represents surface A of the top view? What is the upper-limit dimension between surfaces F and G?
What is the horizontal distance from surface Q to surface T? To what depth into the piece is the dovetail cut? Give dimension Y. At what angle to the horizontal is the dovetail cut? What is the minimum overall height of the dovetailed slide?
What tolerance is allowed on 1. However, most objects are made of several parts assembled together. Many of these assembled parts will be mass produced. An essential element of mass production is interchangeable manufacturing, whereby parts can be made in widely separated locations and then brought together for assembly. It makes modern industry possible, just as effective size control allows interchangeable manufacturing to be accomplished. Unfortunately, it is not possible to make anything to exact size.
Parts can be manufactured with a very high degree of accuracy to within a few millionths of an inch or thousandths of a millimeter , but it is extremely expensive. Fortunately, varying degrees of accuracy determined by functional requirements are all that is needed, not exact sizes. This means that a way of specifying dimensions with whatever degree of accuracy may be required is necessary. This is accomplished through specifications of a tolerance on each dimension, limits on each part, and fits between mating parts.
If allowance and tolerances are properly determined, mating parts can frequently be completely interchangeable. Needing a higher degree of accuracy may require geometric dimension and tolerancing techniques covered in Unit The term fit is produced by an allowance for clearance, interference, and either clearance or interference in what is know as a transition fit. A drawing dimensioned for a fit provides information about the range of tightness between two mating parts.
When the parts move in relation to each other, the dimensions must provide for a positive clearance. The amount of positive clearance depends on the kind of material in the parts, the nature of the motion, lubrication, temperature, and other forces and factors. Machined parts with a positive clearance are dimensioned for a clearance fit.
A negative clearance is required with parts that are to be forced together as a single unit. Parts requiring a negative clearance are dimensioned for an interference fit.
Inch fits are further broken down into five classifications, while there are nine metric. True measurement of a part after it had been produced. Basic Size. Dimension providing a theoretically exact size, form, or position of a surface, point, or fixture. Provides a size from which limits are derived. Clearance Maximum. Loosest fit between two mating parts. Designed Size. Basic size of a feature with tolerances applied. Range of tightness or looseness resulting from allowances and tolerances in mating parts.
Clearance Fit. Clearance always exists between mating parts under all tolerance conditions. Interference Fit. No clearance exists between mating parts under all tolerance conditions. Transition Fit. Depends on the range of limits in which a clearance or interference can exist.
Dimensions related to the largest UL and smallest LL boundary or location acceptable size of a feature. Nominal Size. General dimension used to identify a commercial product. Total amount a part can vary from the basic size and still be usable. Prescribed, intentional difference in the dimensions of mating parts. The result of taking the LL hole size minus the UL of its mating shaft hole.
Lower-Limit 2. Figure 18—1 shows dimensioned pictorials of the other two classes of fit and needed dimensions to determine A an interference fit and B a transition fit. What would this class of fit be called?
If Pin 1 is to have an allowance of 1. UNIT Representing and Dimensioning External Screw Threads 19 Screw threads are used widely 1 to fasten two or more parts securely in position, 2 to transmit power, such as a feed screw, on a machine, 3 to move a scale on an instrument used for precision measurements, and 4 to adjust the alignment of parts.
One of the most common thread forms resembles a V.
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