Projection methods, choosing views, line types and their uses, sectional views, rules for omission, and title blocks. 40 terms, each with meaning, how to write it on the drawing, examples, common mistakes, and JIS vs. ASME differences.
The projection method that places the front view in the center, the top view above it, and the right-side view to its right, so each view sits on the side from which it is viewed. Japanese mechanical drawing uses this method.[1][2][3][4]
Third-angle projection: the top view (seen from above) goes above the front view and the right-side view (seen from the right) goes to its right, so each view sits on the side it is viewed from. In the projection symbol, the circle is on the right.
How to write it on the drawing
Choose the front view and place it in the centerUse the direction that shows the shape of the part best as the front view, and place it in the center of the drawing.[1][2]
Arrange the other views on the side they are viewed fromPut the top view (seen from above) directly above the front view and the right-side view directly to its right; if needed, the left-side view goes on the left and the bottom view below. Align the views with the front view in height and width.[1][2][4]
Draw only the views you needYou do not need to draw all six directions; use the fewest views that define the shape (one-, two-, or three-view drawing).[2][4]
Draw the projection symbol in the title blockDraw the symbol showing a truncated cone seen from two directions (concentric circles and a trapezoid) in the projection field of the title block to show which projection method is used. The arrangement of the symbol is reversed between third-angle and first-angle projection.[2][5][4][6]
ExampleStepped shaft: take the side profile with the center line horizontal as the front view and gather the step and groove dimensions there; add a right-side view to the right of the front view only when the circular end face is needed.(An example built from the rules in the sources)[2]
Common mistakes
Drawing in first-angle projection without the projection symbolWhy: The recipient assumes third-angle projection, and the part is machined with left/right and top/bottom reversed. A manufacturing mistake has actually been reported at a university workshop.Fix: Always draw the projection symbol in the title block. Check that templates in overseas CAD or ISO-based settings are not set to first-angle projection.[3]
Using a face with little information as the front viewWhy: Features of the shape are scattered across several views, and the dimensions are split up and hard to read.Fix: Use the direction with the most shape information, and one that is stable when the part is set down, as the front view.[2][3]
JIS and ASMEIn ASME-based countries (US and Canada), third-angle projection is also the standard, with the same arrangement as JIS. ISO permits both, and the figures in the standard are drawn in first-angle projection (JIS figures use third-angle).[4][3]
Standards: JIS B 0001:2019, 8.3 "Third-angle projection". Projection methods are in the JIS Z 8315 series (Part 2: Orthographic projection). International standard: ISO 128-3; US: ASME Y14.3.[7][8][9][10]
The projection method that places the top view below the front view and the left-side view to the right of the front view, the reverse of third-angle projection. Used mainly in Europe, and also specified in JIS.[4][3]
First-angle projection: the top view goes below the front view and the left-side view to its right, the reverse of third-angle projection. In the projection symbol, the circle is also in the opposite position (on the left).
How to write it on the drawing
Arrange the views in reverse of third-angle projectionPut the top view below the front view and the right-side view to the left of the front view.[4]
Always draw the projection symbolIf you use first-angle projection in Japan, a drawing without the symbol is easily mistaken for third-angle projection.[3]
Common mistakes
Reading a drawing from overseas as if it were third-angle projectionWhy: In first-angle projection the side views are in reversed positions, so you read the shape mirrored.Fix: Check the projection symbol in the title block first. If there is none, infer it from the hidden lines in the front view and similar clues, and confirm with the issuer.[3]
JIS and ASMEIn ASME-based countries (US and Canada), third-angle projection is the standard. You will meet first-angle projection on drawings from Europe and other countries.[4]
Standards: JIS B 0001:2019, 8.4 "First-angle projection"; JIS Z 8315-2 (orthographic projection).[7][8]
The view seen from the direction that best shows the shape and function of the part; it is the reference for the other projected views. Gather dimensions in the front view as far as possible.[2][3][11]
For the front view, choose the direction that best shows the shape of the part. For shafts and cylindrical parts, use the side profile with the center line horizontal as the front view.
How to write it on the drawing
Choose the face with the most informationTake the direction in which the most features are visible as the front.[2]
Use a stable orientationDraw the part in the orientation in which it sits stably.[2]
Shafts and cylindrical parts: center line horizontalFor round parts such as shafts, take the view in which the center line is horizontal as the front view.[2]
Flanges and gears: view perpendicular to the axisFor disk-shaped parts too, take the view seen perpendicular to the axis as the front view.[2]
Common mistakes
Scattering dimensions across several viewsWhy: Machining one feature means comparing several views, which increases misreadings and effort.Fix: Put the dimensions of a feature together in the view where that feature is most clearly seen.[3][11]
Standards: JIS B 0001:2019, 8.2 "Names of projected views" and 10.1 "How to show projected views".[7]
A view projected from the direction facing a surface, such as an inclined face, whose true shape does not appear in the principal views.[12]1 source (for reference)
Auxiliary view: placing a view seen perpendicular to the inclined face beyond that face lets you draw the true shape and size of the face and hole. Draw only the portion you need.
How to write it on the drawing
Project perpendicular to the inclined facePlace the projection plane so that the true shape of the inclined face appears, and draw on it.[12]
Common mistakes
Dimensioning the shape or holes of an inclined face using only the front and side viewsWhy: An inclined face looks foreshortened in the projected views, so the hole shape and position cannot be shown correctly.Fix: Draw an auxiliary view facing the inclined face and put the dimensions there.[12]
Standards: covered in JIS B 0001:2019, 10.1 "How to show projected views" (details could not be confirmed in the preview).[7]
Line types and thicknessessen no shurui to futosatypes of lines / alphabet of lines
Each line on a drawing has its use determined by a combination of shape (continuous, dashed, chain, zigzag, etc.) and thickness (thin, thick, extra-thick). Using lines correctly is the prerequisite for not misreading a drawing.[13][1][14]
A line's use is determined by the combination of shape (continuous, dashed, chain) and thickness (thin, thick, extra-thick). Draw thick and thin lines clearly differently.
How to write it on the drawing
Clearly distinguish thick and thin linesMake a clear difference in thickness between thick lines such as visible outlines and thin lines such as dimension lines (a Tokyo Tech teaching material recommends at least double).[1]
Assign a line type to each useVisible outline = thick continuous line; dimension lines, extension lines, leader lines, hatching = thin continuous line; hidden lines = thin dashed line (or thick dashed line); center lines = thin chain line; phantom lines = thin double-dot chain line; special-requirement lines = thick chain line; break lines = irregular thin wavy line or zigzag line.[13][1][14]
Use extra-thick lines for single-line representation of thin partsUse an extra-thick continuous line when representing a thin part such as steel plate or glass with a single line.[13]
Common mistakes
Drawing everything at the same thicknessWhy: The outline cannot be told apart from dimension lines and the like, and the drawing becomes hard to read.Fix: Clearly separate thick and thin lines, and use line types as intended for each use.[1]
JIS and ASMEUS teaching materials also use a thick continuous line for visible lines, a thin dashed line for hidden lines, a thin long-short chain line for center lines, and a thin double-dot chain line for phantom lines, so the basic correspondence is the same. Some ANSI-style examples draw the cutting-plane line as a thick line.[14]
Standards: JIS B 0001:2019, 6 "Lines" (6.1 Line thickness, 6.2 Line types and uses, 6.3 Line precedence). The basic principles of lines are in JIS Z 8312 (normative reference); international standard: ISO 128-2:2022.[7][15]
Visible outlinegaikeisenvisible line / object line
The line representing the shape of the visible parts of an object. Drawn as a thick continuous line.[13][1][14]
Visible outline: draw the visible outline of the part as a thick continuous line. When it overlaps other lines, keep the visible outline.
How to write it on the drawing
Draw as a thick continuous lineMake it the most prominent line on the drawing.[1][14]
Visible outline takes precedence when lines overlapDraw the visible outline in preference when it overlaps hidden lines or center lines.[14]
Common mistakes
Drawing it as thin as dimension linesWhy: Shape lines and dimension lines cannot be distinguished, and the drawing does not look like a proper drawing.Fix: Make visible outlines thick lines and dimension-related lines thin lines.[1]
Standards: JIS B 0001:2019, 6.2 "Line types and uses".[7]
The line representing the shape of parts of an object that cannot be seen (back side or interior). Drawn as a thin dashed line (or thick dashed line).[13][1][14]
Hidden line: draw invisible holes and internal shapes with a thin dashed line. If the interior is complex, use a sectional view.
How to write it on the drawing
Draw with a thin dashed lineDraw as a series of short dashes at regular intervals.[1][14]
Use a sectional view to show the interiorUse a sectional view when you want to show the internal shape clearly.[16][17]
Common mistakes
Putting dimensions on hidden linesWhy: Dashed lines and dimensions overlap, making both the shape and the dimensions hard to read.Fix: Put dimensions in a view where the feature is visible as a visible outline, or in a sectional view.[3]
Standards: JIS B 0001:2019, 6.2 "Line types and uses".[7]
The line representing the center of a figure or the path along which a center moves. Drawn as a thin chain line. Always add it to the centers of round holes, cylinders, and so on.[13][1][14]
Center line: draw a thin chain line through the center of a shaft or hole, extending slightly beyond the figure. In views where it appears as a circle, draw it as a cross.
How to write it on the drawing
Draw with a thin chain lineAlternate long and short dashes.[13][14]
Round features: in both front and side viewsAdd center lines to round holes, threaded holes, and cylindrical parts in each of the front and side views.[1]
In views where it looks like a circle, use a crossIn a view where a hole appears as a circle, draw two perpendicular center lines through its center.[14][5]
Common mistakes
Leaving center lines off round holesWhy: You cannot tell where the center of the hole is or what the position dimensions are measured from.Fix: Put center lines on every round hole and cylinder.[1]
Standards: JIS B 0001:2019, 6.2 "Line types and uses".[7]
The line representing shapes that do not appear in projection but are shown as an aid to explanation. Drawn as a thin double-dot chain line; used for adjacent parts, positions of tools and fixtures, movement positions of moving parts, shapes before and after machining, etc.[13][14]
Phantom line: draw supplementary shapes for explanation, such as neighboring parts, tools, and moved positions, with a thin double-dot chain line.
How to write it on the drawing
Draw with a thin double-dot chain lineDraw as a repeating pattern of one long line and two short lines.[13][14]
When to use itUsed to show adjacent parts for reference, positions of tools and jigs, specific positions or limits of travel of moving parts, shapes before and after machining, repeated portions, and parts in front of the section plane.[13]
Instead of repeated detailsIt is also used when omitting repeated details such as gear teeth.[14]
ExampleRange of motion of a lever: draw the lever body with visible outlines, overlay the fully swung position with a thin double-dot chain line, and give the swing angle as a dimension.(An example built from the rules in the sources)[13][14]
Common mistakes
Drawing adjacent parts with visible outlinesWhy: The boundary between your part and the neighboring part is unclear, and the neighbor's shape is read as something to be machined.Fix: Draw everything other than your own part with phantom lines.[13][14]
JIS and ASMEThe phantom line in US teaching materials is also a thin double-dot chain line, with the same purpose of showing alternate positions of moving parts and mating parts.[14]
Standards: JIS B 0001:2019, 6.2 "Line types and uses" (centroidal lines are also thin double-dot chain lines).[7][13]
Dimension lines and extension linessunpo-sen, sunpo-hojo-sendimension line / extension line
A dimension line is the line drawn in the direction being measured to enter a dimension; an extension line is the line drawn out from the figure to enter a dimension. Both are drawn as thin continuous lines.[13][1][14]
Draw extension lines from the points being measured, draw the dimension line between them, and put arrowheads at both ends. Both are thin continuous lines. Write the value above the dimension line (to the left for vertical dimensions), in an orientation readable from the right.
How to write it on the drawing
Draw extension lines from the measuring pointsExtend a thin continuous line from the measured point to the dimension line position (US teaching materials start it with a small gap so that it does not touch the part outline).[13][14]
Terminators at both ends of the dimension linePut a terminator such as an arrowhead at the ends of the dimension line (JIS Z 8317-1, 5.3 "Terminators and origin indicators").[18]
Common mistakes
Making people scale dimensions off the drawingWhy: Parts not drawn to scale and print shrinkage or stretch make the measured value differ from the actual dimension.Fix: Enter every needed dimension as a number; do not make people measure the drawing.[11]
Standards: JIS B 0001:2019, 11.2 "Extension lines" and 11.3 "Dimension lines"; JIS Z 8317-1, 5.2–5.4; international standard: ISO 129-1.[7][18][19]
A thin continuous line (including reference lines) for drawing out a note, symbol, or dimension from the place it refers to.[13][14]
Leader line: a thin continuous line drawn diagonally from the feature to carry a note or symbol. Add an arrowhead when it points to a line.
How to write it on the drawing
Draw it diagonally from the point it refers toPlace the arrowhead on the point referred to and draw the line out to the side where the text is written.[14]
Hole callouts follow the leader lineWrite the number of holes, diameter, depth, and counterbore after a leader line drawn from the hole position.[20][21]
Standards: JIS B 0001:2019, 6.2; JIS Z 8317-1, 5.5 "Leader lines".[7][18]
The line showing the boundary where part of an object is broken away or removed. Drawn as an irregular wavy thin continuous line or a zigzag line.[13][14]
Break line: show the boundary where part is broken away to reveal the interior with a thin wavy line (or zigzag line).
How to write it on the drawing
Wavy line at the boundary of a broken-out sectionIn a broken-out section, separate the sectioned area with an irregular thin wavy line.[14][13]
Zigzag lines for omitting the middle of a long partTo omit the middle of a long, uniform part, cut it off with two parallel zigzag lines.[14][13]
JIS and ASMEUS teaching materials use a freehand wavy line for a short break and a straight line with zigzags for a long break, and also use an S-shaped break for cylinders.[14]
Standards: JIS B 0001:2019, 6.2 "Line types and uses".[7]
The line that shows, in the corresponding view, where a section was cut. Drawn as a thin chain line, thickened at both ends and where the direction changes.[13][17][14]
Cutting-plane line: show where the cut was made with a thin chain line, thickened at both ends and at the bends. Put arrows showing the viewing direction and a letter at both ends, and write "A-A" on the section view.
How to write it on the drawing
Show the cutting position with a thin chain lineDraw a cutting-plane line when cutting at a position other than the basic center line.[13][17]
Thicken both ends and the bendsMake the ends and the parts where the direction changes thick lines (no need to thicken if it cannot be confused with other lines).[13][17]
Arrows and letters at both endsShow the viewing direction with arrows, add a letter (such as A), and write something like "Section A-A" near the section view.[17][14]
Common mistakes
Not showing the viewing direction of the sectionWhy: It is unclear from which side the section is viewed, so the shape is read backwards.Fix: Put arrows and a letter at both ends of the cutting-plane line and write the same letter on the section view.[17]
JIS and ASMEIn US (ANSI-style) teaching materials the cutting-plane line is drawn as a thick line, with arrows showing the viewing direction. The ISO/JIS style is a thin chain line with only the ends thick.[14][13]
Standards: JIS B 0001:2019, 6.2 and 10.2 "Sectional views".[7]
Thin continuous lines arranged regularly to distinguish a limited area of a figure, such as the cut face of a section, from the rest.[13][14]
Hatching: draw thin continuous lines diagonally at equal spacing on the cut face. In threads, run them to the line at the thread crests; do not hatch parts that are not sectioned.
How to write it on the drawing
Arrange thin continuous lines at equal spacingFill the cut area with thin parallel lines.[13][14]
Threads: up to the crest lineIn a thread section, extend the hatching to the thick continuous line representing the thread crests.[22]
Do not hatch parts that are not cutDo not hatch the cut face of parts that are not sectioned lengthwise, such as shafts, pins, bolts, and keys, or of thin ribs and spokes.[17][16]
Common mistakes
Stopping the hatching in a thread at the root lineWhy: You can no longer tell the crests of the thread from the roots.Fix: Extend the hatching to the thick line of the thread crests.[22]
Standards: JIS B 0001:2019, 6.2 and 10.2 "Sectional views".[7]
Special-requirement linetokushu-shitei-senthick chain line / chain line
The line showing the range to which a special requirement such as heat treatment applies. Drawn as a thick chain line.[13][14]
Special-requirement line: draw a thick chain line slightly off the outline along the range of a special requirement such as hardening, and add a note.
How to write it on the drawing
Draw a thick chain line along the rangeDraw a thick chain line along the range where the requirement applies and note the requirement with a leader line (JIS B 0001:2019 has the item 11.11 "Indication of machining and treatment ranges").[13][14][7]
ExampleHardening only the bearing section of a shaft: draw a thick chain line along the outline of that range, give the length of the range as a dimension, and add the note "induction hardening".(An example built from the rules in the sources)[13][14]
JIS and ASMEUS teaching materials use the same thick chain line to indicate the range of special treatment and also the extent of a projected tolerance zone. A JIS-based explanation (KEYENCE) draws the projected portion with a thin double-dot chain line.[14][23]
Standards: JIS B 0001:2019, 6.2 and 11.11 "Indication of machining and treatment ranges".[7]
Line precedencesen no yusen jun-iprecedence of lines
The rule for which line to draw when lines of different types overlap at the same position. Visible outlines take precedence over hidden lines and center lines, and hidden lines take precedence over center lines.[14]1 source (for reference)
When lines of different types overlap, give precedence in the order visible outline, hidden line, cutting-plane line, center line, centroidal line, extension line, and draw only the higher-priority line.
How to write it on the drawing
Draw only the higher-priority line when they overlapPriority is visible outline, hidden line, center line, in that order; keep only the higher-priority line.[14]
Common mistakes
Trying to draw both overlapping linesWhy: The lines are doubled and you cannot tell which shape is meant.Fix: Draw only the line with priority.[14]
Standards: JIS B 0001:2019, 6.3 "Line precedence" (details of the order could not be confirmed in the preview).[7]
A sectional view drawn by imagining the part cut completely by one plane, showing the cut face and the shape visible beyond it.[16][17]
Full section: imagine the part cut by one plane at the center line, and draw the cut face (hatching) and the shape visible beyond it. Interiors with many hidden lines can also be read from visible outlines.
How to write it on the drawing
As a rule, cut at the basic center lineAs a rule, draw sections by cutting at the basic center line. When cutting elsewhere, show the position with a cutting-plane line.[17]
Hatching on the cut faceShow the cut face with hatching in thin continuous lines.[13][16]
Common mistakes
Confusing full section with half sectionWhy: People often wrongly call a half section (cut only on one half) a "full section cut in half".Fix: Keep them distinct: a full section cuts the whole part; a half section shows one half as a section, bounded by the center line.[16]
Standards: JIS B 0001:2019, 10.2 "Sectional views"; ISO 128-3.[7][9]
A view of a symmetric part drawn with one half as an outside view and the other half as a section, divided by the center line of symmetry. The outer and inner shapes are shown in one view.[16]1 source (for reference)
Half section: for a part symmetric top and bottom (or left and right), draw one half as a section and the other half as an outside view, divided by the center line of symmetry. The outer and inner shapes are both clear in a single view.
How to write it on the drawing
Divide at the center line of symmetryDraw one side of the center line as a section and the opposite side as an outside view.[16]
Common mistakes
Calling a half section a full sectionWhy: The extent of the section is misread.Fix: Use the names and their extents correctly.[16]
Standards: JIS B 0001:2019, 10.2 "Sectional views".[7]
Broken-out sectionbubun-danmenzubroken-out section / local section
A view that breaks away only part of an outside view to show the interior of the needed area as a section. The boundary is shown with a break line.[16][14][13]
Broken-out section: break away only part of an outside view to show the interior of the needed area (here, a blind hole) as a section. Draw the boundary with a thin wavy break line.
How to write it on the drawing
Break away only the area you want to showSeparate the area with an irregular thin wavy break line and hatch only inside it.[14][13]
Standards: JIS B 0001:2019, 10.2 "Sectional views".[7]
A section view that rotates the cut face of an arm, rib, shaft, etc. by 90° to show it. It can be drawn overlaid on the figure or drawn outside the figure.[13][16]
Revolved section: show the cut face of an arm rotated by 90°. Use a thin continuous line when overlaying it in the view and a thick continuous line when drawing it outside, and show the cutting position with an extension of the center line or similar.
How to write it on the drawing
Use a thin continuous line when overlaying it in the viewWhen the cut face is rotated 90° and overlaid on the figure, draw its outline with a thin continuous line (revolved-section outline).[13]
Show the position when drawing it outside the viewShow the cutting position with a cutting-plane line or an extension of the center line, and when drawing it away from the figure, match them with a letter.[16][17]
Standards: JIS B 0001:2019, 10.2 "Sectional views".[7]
A section view cut with the cutting plane bent or combined partway, in order to show holes or grooves that are not in a line in one section view.[16][17]
Section by combined planes: bend the cutting-plane line to show holes that are not in a straight line in one section view. Thicken the ends and bends of the cutting-plane line, and do not draw the line at the bend in the section view.
How to write it on the drawing
Bend the cutting-plane lineBend the cutting-plane line partway and make the bends thick lines.[17][13]
Do not draw the bend in the section viewIn the section view, do not draw the line at the bend of the cutting plane.[16]
Show features arranged around the center by rotating themHoles or ribs arranged around a center may be rotated onto the cutting plane and shown in true shape.[16]
Standards: JIS B 0001:2019, 10.2 "Sectional views".[7]
Parts not sectioned lengthwisenagate-hoko ni setsudan shinai buhinparts not sectioned
Even in a section view, parts for which cutting does not aid understanding are drawn uncut as outside views. Shafts, pins, bolts, nuts, rivets, keys, and the like fall under this, and thin ribs and spokes are also not treated as cut faces.[17][16]
Even in a section view, parts such as bolts, nuts, shafts, pins, and keys, which do not become clearer when cut, are drawn as outside views without hatching.
How to write it on the drawing
Draw as outside viewsEven in a section view, draw these parts with visible outlines, uncut and without hatching.[17][16]
Common mistakes
Hatching even bolts and shafts in an assembly sectionWhy: The boundaries between parts become hard to see.Fix: Do not section bolts, shafts, keys, etc. lengthwise; draw them as outside views.[17]
Standards: JIS B 0001:2019, 10.2 "Sectional views".[7]
Symmetry symboltaisho-zushi-kigosymmetry symbol / symmetry line
The symbol showing that a symmetric part is drawn on only one side. Two short parallel lines, perpendicular to the center line, are added at both ends of the center line of symmetry.[14]1 source (for reference)
Symmetry symbol: for a symmetric part, draw only one side of the center line of symmetry and add two short perpendicular parallel lines at each end of the center line to show that the rest is omitted.
How to write it on the drawing
Draw only one sideDraw only the shape on one side of the center line of symmetry.[14]
Double lines at both ends of the center lineAt both ends of the center line, draw two short perpendicular parallel lines each.[14]
Standards: JIS B 0001:2019, 10.3 "Omission of figures"; JIS Z 8317-1, 7.8 "Symmetrical parts" (details could not be confirmed in the preview).[7][18]
Simplified representation of repeated featureskurikaeshi zukei no shoryakurepetitive features / equally spaced features
An abbreviation used when identical holes and the like are lined up: draw only the ends or key points, show the other positions with pitch lines and center lines, and state the number as a numeral.[20][24]
Omission of repeated features: for six φ6.6 holes equally spaced on a φ60 pitch circle, draw only one, write "6-φ6.6" with a leader line, and show the others by position only with center lines.
How to write it on the drawing
Draw only the ends or key pointsIf there is no risk of misreading, draw only the ends (one pitch's worth on one side) or key points in true shape.[20]
Quantity is "total-dimension"With a leader line, write the total, a dash, and the hole dimension in that order, as in "6-φ9".[20][1]
When equally spaced on a circleShow the pitch circle diameter, the quantity, and that they are equally spaced (US teaching materials abbreviate this as EQL SP).[24]
ExampleSix φ6.6 holes equally spaced on a φ60 pitch circle: draw the pitch circle with a thin chain line, draw only one hole, write "6-φ6.6" with a leader line, and give the pitch circle diameter φ60 as a dimension.(An example built from the rules in the sources)[20][24]
Common mistakes
Placing corner holes along the arc of the outlineWhy: Each hole needs separate locating, which raises machining cost.Fix: Place them at positions where locating can be done together, such as intersections of edges.[20]
Standards: JIS Z 8317-1, 7.7 "Repeated features at equal intervals"; JIS B 0001:2019, 10.3 "Omission of figures" and 11.14 "Dimensions of identical features".[18][7]
Omitting the middle portionchukanbu no shoryakuconventional break / long break
An abbreviation that cuts out a long section of identical cross-section, as in a shaft or structural shape, with break lines and draws it shortened. This lets you draw at a larger scale.[14][13]
Omitting the middle: for a shaft with a long section of identical cross-section, cut out the middle with break lines and draw it shortened so it can be shown at a larger scale. Write the dimension value as the actual length.
How to write it on the drawing
Cut out the uniform section with two break linesOmit the portion between two parallel break lines.[14]
Standards: JIS B 0001:2019, 10.3 "Omission of figures".[7]
The ratio of the length drawn on the drawing to the actual length. Write it in the title block, like "1:2". Read the shape from the dimension values entered, not from the size of the drawing.[2][5][11]
Write the scale in the title block, like "1:2". Read the shape from the dimension values entered, not from the size of the drawing.
How to write it on the drawing
Write it in the title blockWrite full size as 1:1 and reduction as 1:2, etc.[2]
Detail views use a different scaleWrite the scale near an enlarged detail view of a small portion (example: Detail B (2:1)).[5]
Common mistakes
Making people scale dimensions off the drawingWhy: Differences in scale and print shrinkage or stretch make the result not match the actual part.Fix: Enter every needed dimension as a number.[11]
Drawing in slide-making softwareWhy: The aspect ratio and scale disagree with the entered dimensions, so the appearance and the finished product differ.Fix: Draw in CAD and check which software was used.[3]
Standards: JIS B 0001:2019, 9 "Scales" (the scale standard is JIS Z 8314). For dimensions not proportional to scale, see JIS Z 8317-1, 7.10.[7][18]
The block placed at the lower right of the drawing for writing the part name, drawing number, scale, projection, material, quantity, creator and date, checking and approval, etc.[2][6]
Title block: placed at the lower right of the drawing; contains the part name, drawing number, scale, projection symbol, material, quantity, drafter and date, approval, etc. A general tolerance field is often placed nearby.
How to write it on the drawing
Place at the lower rightPlace it at the lower right of the drawing border.[6][2]
Items to fill inPart name (product name for an assembly drawing), sheet size, scale, drawing number, quantity, material, projection symbol, drafter, checker and approver with dates, company name.[2]
General tolerance and surface texture fieldsMany drawing borders place a general tolerance field and a general surface texture note near the title block.[2][6]
Common mistakes
Leaving the projection or scale blankWhy: The reader has to guess the projection or scale, which causes misreading.Fix: Always fill in the projection symbol and scale.[3][2]
JIS and ASMEUS teaching materials introduce a method in which the tolerance field in the title block sets the tolerance by number of decimal places (for example ±0.02 for two places). JIS indicates it collectively by the general tolerance standard and grade.[6][25]
Standards: JIS B 0001:2019, 5.2 "Drawing format" (sheet sizes and formats are in JIS Z 8311).[7]
Drawing corrections and revisionszumen no teisei, henkodrawing revision / drawing change
When correcting a drawing after issue, record on the drawing where and which revision it was. A Shimane University teaching material shows an example of marking the corrected spot with a symbol (a triangle revision mark) that has the revision number inside a triangle.[2]1 source (for reference)
Drawing correction: next to a dimension changed after issue, add a symbol with the revision number inside a triangle, and record the content and date with the same symbol in the revision block (example from a Shimane University teaching material).
How to write it on the drawing
Mark the corrected spot with a symbolNear the corrected dimension, add a symbol with the revision number inside a triangle.[2]
Standards: JIS B 0001:2019, 14 "Drawing corrections and revisions" (details could not be confirmed in the preview).[7]
Assembly drawings and part drawingskumitatezu to buhinzuassembly drawing / detail drawing / part drawing
An assembly drawing shows how parts are combined and the main related dimensions; a part drawing shows everything needed to make one part: shape, dimensions, tolerances, material, and finish. A part drawing corresponds to a work instruction.[1][26][7]
How to write it on the drawing
Decide dimensions on the assembly drawing, then go to part drawingsDecide each part's dimensions on the assembly drawing and draw the part drawings from that information.[1]
Overall assembly drawing: representative dimensionsPut in representative dimensions used for delivery and layout, such as the overall outline of the equipment and the width with doors open.[26]
Subunit assembly drawings: more related dimensionsIncluding many related dimensions in the assembled state makes it easier to cross-check the part drawings.[26]
Common mistakes
Making do with a rough sketch that only you understand as the part drawingWhy: The intent does not reach the machinist, and the part has to be remade.Fix: Make a part drawing from which anyone can make the same thing.[1]
Standards: JIS B 0001:2019 mainly covers drawing of part drawings and assembly drawings (scope).[7]
A symbol placed before the dimension value to show what the dimension represents (diameter, radius, side of a square, chamfer, plate thickness, counterbore, hole depth, etc.).[21][27]
Write the dimension symbol before the dimension value to show whether it is a diameter (φ), radius (R), side of a square (□), 45° chamfer (C), spherical radius (SR), or plate thickness (t).
How to write it on the drawing
Write it before the valueWrite the symbol before the dimension value.[21]
Symbols and their Japanese readingsφ (maru, fai) diameter, Sφ (esu-maru) spherical diameter, □ (kaku) side of a square, R (aru) radius, CR (shi-aru) controlled radius, SR (esu-aru) spherical radius, ⌒ (enko) arc length, C (shi) 45° chamfer, t (ti) thickness, ⌴ (zaguri, fukazaguri) counterbore / spotface, ⌵ (sarazaguri) countersink, ↧ (ana-fukasa) depth.[21]
Symbols added in the 2010 revisionThe symbols for CR, counterbore, countersink, and hole depth were added in JIS B 0001:2010.[21]
Common mistakes
Using φ for an arc of a semicircle or lessWhy: φ is the symbol for the diameter of a circle or of an arc over 180°.Fix: Specify arcs of 180° or less by radius R.[21]
JIS and ASMEUS teaching materials also use symbols of the same shape for square (□), counterbore/spotface (⌴), countersink (⌵), and depth (↧). ASME adds SF to the counterbore symbol to distinguish a shallow spotface, whereas JIS expresses both counterbore and deep counterbore with the same symbol.[27][21][28]
Standards: JIS B 0001:2019, 11.6 "Dimension symbols"; JIS Z 8317-1, 7.1–7.6.[7][18]
⌴Counterbore and spotfacezaguri, fukazaguricounterbore / spotface
A step machined at the entrance of a hole with a larger diameter. A deep one to sink a bolt head is a counterbore; a shallow one to flatten the seat surface for a bolt or nut is a spotface.[27][21][29]
For hole dimensions, draw a leader from the view where the hole appears as a circle and write the hole diameter followed in one run by the symbols and values for counterbore, countersink, and depth (the symbols were added in JIS B 0001:2010).
How to write it on the drawing
Follow the hole callout with symbolsWrite the hole diameter, the counterbore diameter after ⌴, and the depth after ↧ in one run on a leader line (for the details of the order, see JIS B 0001, 11.7 "Dimensioning holes").[21][27][7]
JIS and ASMEASME distinguishes a spotface (shallow counterbore) by adding SF to ⌴ (KEYENCE also lists SF as the symbol for "shallow spotface (ASME only)"). JIS expresses both counterbore and deep counterbore with ⌴.[27][28][21]
Standards: JIS B 0001:2019, 11.6 and 11.7. Bolt hole and counterbore diameters are in JIS B 1001 "Bolt hole diameters and counterbore diameters".[7][21][30]
A hole entrance widened into a cone to sink the head of a countersunk screw.[27][21]
For hole dimensions, draw a leader from the view where the hole appears as a circle and write the hole diameter followed in one run by the symbols and values for counterbore, countersink, and depth (the symbols were added in JIS B 0001:2010).
How to write it on the drawing
After the ⌵ symbol, the entrance diameter and angleShows the entrance diameter and included angle of the countersink.[27][24][21]
JIS and ASMEASME also uses the same ⌵ symbol (it was formerly abbreviated CSK).[27]
The symbol showing the depth of a hole, counterbore, or groove. Write the depth value after ↧.[21][27]
For hole dimensions, draw a leader from the view where the hole appears as a circle and write the hole diameter followed in one run by the symbols and values for counterbore, countersink, and depth (the symbols were added in JIS B 0001:2010).
How to write it on the drawing
Depth after the symbolAfter the hole diameter or counterbore callout, write the depth value after ↧.[21][27]
JIS and ASMEASME also uses a depth symbol of the same shape; older drawings may abbreviate it as DP.[27]
Standards: JIS B 0001:2019, 11.6 and 11.7 (made a symbol in JIS B 0001:2010).[7][21]
A radius specification that controls the radius so that the straight and arc portions blend smoothly and the radius stays between the maximum and minimum permissible radii. Write CR followed by the radius.[21]1 source (for reference)
How to write it on the drawing
Radius after CRWrite CR before the radius value.[21]
JIS and ASMEIn ASME Y14.5-2018, the treatment of radius tolerance was changed (5.16).[31]
Standards: JIS B 0001:2019, 11.6 (added in JIS B 0001:2010).[7][21]
A method of entering dimensions linked one after another from feature to feature. Since the tolerances of the individual dimensions add up, the variation in the distance from end to end becomes large.[11][32]1 source (for reference)
Chain dimensioning: dimensions are linked from one feature to the next. Because each dimension's tolerance adds up, the variation of the length between the two ends becomes large.
How to write it on the drawing
Line up dimension lines in a rowList the dimensions between adjacent features in order.[11]
If you need the overall length, use a reference dimensionGiving the overall length with a tolerance as well causes a contradiction, so either omit one of them or make it a reference dimension in parentheses.[32][3]
ExampleIf three lengths in a chain are each ±0.1, the length between the ends can vary by up to ±0.3.(An example built from the rules in the sources)[32]
Common mistakes
Linking functionally important distances with chain dimensionsWhy: Tolerances accumulate and the important distance drifts off target.Fix: Specify important distances directly from a datum (with parallel dimensions), or with TEDs (basic dimensions) and position tolerance.[32][1][33]
Standards: JIS Z 8317-1:2008, 8.4 "Chain dimensioning".[18]
A method of entering dimensions from a common datum (an end face or center) to each feature. The tolerance of each dimension does not affect the others.[11][1][34]
Parallel dimensioning: dimensions are listed from a common datum (here the left end face) to each position. No dimension's tolerance affects the others.
How to write it on the drawing
Decide the datum faceChoose the datum by considering the face that mates in assembly, the starting point for layout and measurement, and the face placed against the machine tool table.[1]
Give dimensions from the datum to each positionList the distances from the same datum to each feature.[11][1]
ExampleTaking the left end face as the datum and giving step positions as distances from the left end, such as 20, 45, and 80, fixes each step's position directly within its ± tolerance.(An example built from the rules in the sources)[11]
Standards: JIS Z 8317-1:2008, 8.2 "Parallel dimensioning" (8.3 "Running dimensioning" and 8.5 "Coordinate dimensioning" are also ways of dimensioning from a datum).[18]
A method of showing hole positions and the like by X and Y coordinates from the datum, collected in a table. It keeps the drawing uncluttered for parts with many holes.[11]1 source (for reference)
Coordinate dimensioning: hole positions are tabulated as X and Y coordinates from the datum (origin). Marking holes with symbols to match the drawing with the table keeps the drawing clean even for parts with many holes.
How to write it on the drawing
Label the holes and collect them in a tableLabel each hole and tabulate the X and Y coordinates from the datum and the hole dimensions.[11]
Standards: JIS Z 8317-1:2008, 8.5 "Coordinate dimensioning" and 5.8 "Tabular dimensioning".[18]
A dimension without a tolerance, given to aid understanding. The value is enclosed in parentheses and is not used for acceptance judgment.[32][3]
Reference dimension: a dimension without a tolerance given to aid understanding. Enclose the value in parentheses; it is not used to judge acceptance.
How to write it on the drawing
Enclose in parenthesesEnclose the value in parentheses, like (25).[32]
Use it for redundant or contradictory dimensionsMake a dimension that can be calculated from other dimensions, or that would contradict when general tolerances are applied, a reference dimension.[32][3]
Common mistakes
Judging acceptance by a reference dimensionWhy: A reference dimension has no tolerance of its own; it is a value in which the tolerances of other dimensions accumulate.Fix: Judge acceptance by the other toleranced dimensions.[32]
JIS and ASMEUS teaching materials also introduce, besides parentheses, writing REF after the value.[32]
Standards: JIS Z 8317-1:2008, 7.11 "Reference dimensions".[18]
A state in which a dimension is defined twice, such as writing the same dimension in several views or writing the overall length and all the partial dimensions with tolerances. It clutters the drawing and makes the tolerances contradict each other.[3][32][1]
Redundant dimensions: if the overall length and all partial dimensions are given with tolerances, the same length is defined twice and the tolerances contradict each other. Give each dimension in one place.
How to write it on the drawing
Give each dimension in one placeWrite the same dimension just once, in the view where the shape is seen best.[3][1]
Make the overall length a reference dimensionAn overall length determined by the partial dimensions should be a reference dimension in parentheses.[32][3]
Common mistakes
Giving the overall length and every step dimension with tolerancesWhy: The sum of the step tolerances does not agree with the overall length tolerance, so it cannot be decided which to hold.Fix: Omit one non-critical dimension or make it a reference dimension.[32][3]
Writing the same dimension in both the front and side viewsWhy: The drawing becomes cluttered, and when correcting, only one gets fixed and they disagree.Fix: Write each dimension in only one place.[3][1]
Standards: JIS Z 8317-1:2008, 4 "Principles of dimensioning and tolerancing".[18]
Dimensioning holesana no sunpo no arawashikatahole callout
A way of writing the hole diameter, quantity, depth, counterbore, etc. in a row with symbols on a leader line drawn from the hole position. JIS B 0001:2010 made it possible to write hole depth, counterbore, and countersink with symbols.[21][20][1]
For hole dimensions, draw a leader from the view where the hole appears as a circle and write the hole diameter followed in one run by the symbols and values for counterbore, countersink, and depth (the symbols were added in JIS B 0001:2010).
How to write it on the drawing
Quantity: total and a dashWrite the total, a dash, and the dimension in that order, like "4-φ5.5".[20][1]
Depth and counterbore by symbolUse ↧ for depth, ⌴ for counterbore, and ⌵ for countersink.[21]
Common mistakes
Making the mating hole a threaded hole as wellWhy: The bolt engages both and cannot be assembled.Fix: Make one side a clearance hole for the bolt to pass through and put the thread only on the mating side.[3][1]
Standards: JIS B 0001:2019, 11.7 "Dimensioning holes".[7]
Explanations without a mark are those on which two or more sources from different publishers agree. Because the text of the standards is paid, they were checked against technical materials from measuring-instrument and parts manufacturers, teaching materials from universities and public testing institutes, and public pages of the standards, and the explanations are written in Kezuriba's own words. The diagrams of the entry fields were drawn by Kezuriba.