Craftsman Computer Aided Mechanical Drawing cheat sheet

ISO 5457 defines A-series sheet sizes: A0 is 1189 × 841 mm; each subsequent size halves the larger dimension (A4 = 297 × 210 mm).

ISO 128 line types: continuous thick for visible edges, continuous thin for dimension and extension lines, dashed for hidden edges, chain thin for centre lines and cutting planes.

First-angle projection (ISO, used in Europe/Asia) places the view on the far side of the object; third-angle (ASME, US/Canada) places it on the near side.

Preferred drawing scales per ISO 5455: 1:1, 1:2, 1:5, 1:10, 1:20, 1:50, 1:100 and enlargements 2:1, 5:1, 10:1; scale is marked in the title block.

Standard lettering height h = 2.5, 3.5, 5, 7, 10 mm; lowercase height is 0.7h and stroke width d = 0.1h for style A.

A title block per ISO 7200 carries drawing title, drawing number, sheet size, scale, projection symbol, revision, and approval signatures.

ASME Y14.5 governs dimensioning and tolerancing in US practice; ASME Y14.1 defines inch sheet sizes (A = 8.5 × 11 in through E).

The projection symbol (truncated cone in two views) must appear in the title block to declare first- or third-angle arrangement.

Model space holds full-scale geometry; paper space (layout) holds title block and viewports at the plotted scale, so the viewport scale must equal the drawing scale.

Absolute coordinates are X,Y from the origin; relative coordinates use @dX,dY; polar coordinates use @distance<angle measured counter-clockwise from +X.

Object snaps (endpoint, midpoint, centre, intersection, perpendicular, tangent) constrain picks to exact geometry and should be the default input method over free picking.

A CAD layer carries colour, linetype, lineweight, and on/off/freeze/lock state; freeze and off differ because frozen layers are not regenerated, improving performance.

Blocks are named, reusable symbol definitions; editing the block definition updates all insertions, while exploded copies lose that link.

Drawing templates (DWT) store units, layers, dimension styles, text styles, and layouts so new drawings inherit a consistent environment.

Drawing exchange relies on DXF (text-based, widely compatible) and DWG (native); PDF is for review and plotting, not for editable exchange.

Unit settings must be set before drawing: millimetres with 0.0 precision for metric mechanical work; inserting a drawing in different units scales geometry by the unit ratio.

To bisect a line: strike equal arcs from both endpoints with radius greater than half the length; the arc intersections define the perpendicular bisector.

To divide a line into n equal parts: draw an auxiliary line at any angle, step off n equal divisions, connect the last division to the far endpoint, then draw parallels.

To construct a regular hexagon given the circumscribed circle: step the compass around the circle at the radius; the hexagon side equals the circumradius.

To find the centre of an arc: draw two chords and erect their perpendicular bisectors; the intersection is the centre.

A tangent to a circle at a point is perpendicular to the radius drawn to that point; external tangents between two circles are constructed with an auxiliary circle of radius R − r.

An ellipse with major axis AB and minor axis CD is drawn by the concentric-circle or four-centre method; the trammel method uses the relation of the semi-axes.

An involute of a circle is generated by unwinding a taut string from the circumference; used for gear tooth profiles.

A parabola is the locus of points equidistant from a focus and a directrix; a hyperbola has a constant difference of distances to two foci.

Six principal views are front, top, bottom, right side, left side, and rear; the front view is chosen to show the most characteristic shape and fewest hidden lines.

In third-angle projection the top view sits above the front view and the right-side view sits to the right; in first-angle the top view is below and the right-side view is on the left.

Alignment rule: views share projection lines, so width aligns between front and top, height between front and side, and depth between top and side.

Hidden edges are drawn as dashed lines only when needed for clarity; they are omitted where a visible line or centre line coincides.

An inclined surface appears foreshortened in all principal views and true shape only in an auxiliary view perpendicular to it.

A line parallel to a plane of projection shows true length in that view; a line perpendicular to a plane projects as a point.

Centre lines mark axes of symmetry and hole centres, extending about 3 mm past the feature outline, using long-dash–short-dash pattern.

The miter line at 45° transfers depth from the top view to the side view in manual layout.

Dimension lines are unbroken thin lines terminated by arrowheads; extension lines start about 1 mm from the object and extend about 2 mm beyond the dimension line.

Place dimensions on the view that shows the feature's true shape; never dimension a hidden line if a visible view can carry it.

Nominal size plus deviation notation: shaft 30 −0.020/−0.041 means limits 29.980 and 29.959 mm; tolerance is the difference of the limits, 0.021 mm.

ISO hole-basis fits use uppercase hole letters (H) with lowercase shaft letters (h, g, f, k, n, p); H7/g6 is a close running fit, H7/p6 an interference fit.

Fit types: clearance (hole minimum > shaft maximum), transition (zones overlap), interference (shaft minimum > hole maximum).

Geometric tolerances per ISO 1101 / ASME Y14.5 use a feature control frame: symbol, tolerance value, and datum references in that order.

Maximum material condition (MMC) is the largest shaft / smallest hole; least material condition (LMC) is the opposite; bonus tolerance applies when departing from MMC.

Surface roughness Ra is the arithmetic mean deviation of the profile, expressed in micrometres and marked with the ISO 1302 check-mark symbol.

A full section cuts the object completely with one cutting plane; the hatched area represents material actually cut, not surfaces behind the plane.

A half section removes one quarter of the object and is used for symmetric parts; the cut half and outside half are separated by a centre line, not a visible line.

A broken-out section is bounded by a thin irregular freehand or spline break line and exposes only a local feature such as a hole.

Hatching lines are thin, uniformly spaced at about 45°, and adjacent parts in an assembly are hatched in opposite directions or at different spacings.

Section lines, ribs, webs, shafts, bolts, nuts, and pins are not hatched when cut longitudinally; this convention avoids the appearance of solid thickness.

A cutting plane is shown by a chain thick line with arrows indicating viewing direction and identifying capital letters; the resulting view is labelled A–A.

An auxiliary view is projected perpendicular to an inclined surface from a primary view, giving true shape; a partial auxiliary shows only the inclined face.

Conventional breaks (S-break for round bars, zigzag for rectangular) shorten long uniform parts while retaining the true dimension value.

A detail drawing shows one part with all dimensions, tolerances, surface finish, material, and heat treatment needed for manufacture.

An assembly drawing shows the relationship and position of parts, with a parts list (item number, description, quantity, material, standard) and balloon leaders.

Balloon leaders terminate on the part with a dot or arrowhead and point to a circle containing the item number; they never cross each other.

Standard fasteners are drawn simplified: bolt heads and nuts are not shown in true projection, and threaded holes use the conventional major/minor diameter representation.

A thread is shown by a thick continuous line for the crest and a thin continuous line for the root, with the root line at 0.85 of the major diameter on external threads.

Running fits between moving parts, keyway and spline connections, and bearing seats require the appropriate ISO fit designation on the assembly.

Section views in assemblies distinguish adjacent parts by hatching direction and spacing; standard parts such as bolts and bearings are left unhatched.

Exploded isometric views with item balloons link assembly sequence to the parts list and are common in service documentation.

Plot scale 1:1 in paper space means one drawing unit equals one millimetre on paper; the viewport scale, not the plot scale, sets the drawing scale.

Plot style tables (CTB for colour-dependent, STB for named) map object colour or style to plotted lineweight and screening.

Lineweight display on screen is cosmetic; plotted lineweights come from the plot style or object lineweight property, typically 0.25 mm thin and 0.5 mm thick.

PDF output should embed fonts and use vector output; raster plotting at 300 dpi or lower degrades fine linework and small text.

A revision table records revision letter, date, description, and approver; revision clouds and triangles mark changed areas on the sheet.

Drawing numbers must be unique and traceable; ISO 7200 title block fields include legal owner, drawing number, revision index, and sheet number of total.

Plot preview verifies sheet margins, viewport clipping, and that no geometry falls outside the printable area before release.

Archiving requires the native file plus a neutral format (PDF/DXF) and a bill of materials so the drawing remains readable without the CAD system.

ISO 5457 defines A-series sheet sizes: A0 is 1189 × 841 mm; each subsequent size halves the larger dimension (A4 = 297 × 210 mm).

ISO 128 line types: continuous thick for visible edges, continuous thin for dimension and extension lines, dashed for hidden edges, chain thin for centre lines and cutting planes.

First-angle projection (ISO, used in Europe/Asia) places the view on the far side of the object; third-angle (ASME, US/Canada) places it on the near side.

Preferred drawing scales per ISO 5455: 1:1, 1:2, 1:5, 1:10, 1:20, 1:50, 1:100 and enlargements 2:1, 5:1, 10:1; scale is marked in the title block.

Standard lettering height h = 2.5, 3.5, 5, 7, 10 mm; lowercase height is 0.7h and stroke width d = 0.1h for style A.

A title block per ISO 7200 carries drawing title, drawing number, sheet size, scale, projection symbol, revision, and approval signatures.

ASME Y14.5 governs dimensioning and tolerancing in US practice; ASME Y14.1 defines inch sheet sizes (A = 8.5 × 11 in through E).

The projection symbol (truncated cone in two views) must appear in the title block to declare first- or third-angle arrangement.

Model space holds full-scale geometry; paper space (layout) holds title block and viewports at the plotted scale, so the viewport scale must equal the drawing scale.

Absolute coordinates are X,Y from the origin; relative coordinates use @dX,dY; polar coordinates use @distance<angle measured counter-clockwise from +X.

Object snaps (endpoint, midpoint, centre, intersection, perpendicular, tangent) constrain picks to exact geometry and should be the default input method over free picking.

A CAD layer carries colour, linetype, lineweight, and on/off/freeze/lock state; freeze and off differ because frozen layers are not regenerated, improving performance.

Blocks are named, reusable symbol definitions; editing the block definition updates all insertions, while exploded copies lose that link.

Drawing templates (DWT) store units, layers, dimension styles, text styles, and layouts so new drawings inherit a consistent environment.

Drawing exchange relies on DXF (text-based, widely compatible) and DWG (native); PDF is for review and plotting, not for editable exchange.

Unit settings must be set before drawing: millimetres with 0.0 precision for metric mechanical work; inserting a drawing in different units scales geometry by the unit ratio.

To bisect a line: strike equal arcs from both endpoints with radius greater than half the length; the arc intersections define the perpendicular bisector.

To divide a line into n equal parts: draw an auxiliary line at any angle, step off n equal divisions, connect the last division to the far endpoint, then draw parallels.

To construct a regular hexagon given the circumscribed circle: step the compass around the circle at the radius; the hexagon side equals the circumradius.

To find the centre of an arc: draw two chords and erect their perpendicular bisectors; the intersection is the centre.

A tangent to a circle at a point is perpendicular to the radius drawn to that point; external tangents between two circles are constructed with an auxiliary circle of radius R − r.

An ellipse with major axis AB and minor axis CD is drawn by the concentric-circle or four-centre method; the trammel method uses the relation of the semi-axes.

An involute of a circle is generated by unwinding a taut string from the circumference; used for gear tooth profiles.

A parabola is the locus of points equidistant from a focus and a directrix; a hyperbola has a constant difference of distances to two foci.

Six principal views are front, top, bottom, right side, left side, and rear; the front view is chosen to show the most characteristic shape and fewest hidden lines.

In third-angle projection the top view sits above the front view and the right-side view sits to the right; in first-angle the top view is below and the right-side view is on the left.

Alignment rule: views share projection lines, so width aligns between front and top, height between front and side, and depth between top and side.

Hidden edges are drawn as dashed lines only when needed for clarity; they are omitted where a visible line or centre line coincides.

An inclined surface appears foreshortened in all principal views and true shape only in an auxiliary view perpendicular to it.

A line parallel to a plane of projection shows true length in that view; a line perpendicular to a plane projects as a point.

Centre lines mark axes of symmetry and hole centres, extending about 3 mm past the feature outline, using long-dash–short-dash pattern.

The miter line at 45° transfers depth from the top view to the side view in manual layout.

Dimension lines are unbroken thin lines terminated by arrowheads; extension lines start about 1 mm from the object and extend about 2 mm beyond the dimension line.

Place dimensions on the view that shows the feature's true shape; never dimension a hidden line if a visible view can carry it.

Nominal size plus deviation notation: shaft 30 −0.020/−0.041 means limits 29.980 and 29.959 mm; tolerance is the difference of the limits, 0.021 mm.

ISO hole-basis fits use uppercase hole letters (H) with lowercase shaft letters (h, g, f, k, n, p); H7/g6 is a close running fit, H7/p6 an interference fit.

Fit types: clearance (hole minimum > shaft maximum), transition (zones overlap), interference (shaft minimum > hole maximum).

Geometric tolerances per ISO 1101 / ASME Y14.5 use a feature control frame: symbol, tolerance value, and datum references in that order.

Maximum material condition (MMC) is the largest shaft / smallest hole; least material condition (LMC) is the opposite; bonus tolerance applies when departing from MMC.

Surface roughness Ra is the arithmetic mean deviation of the profile, expressed in micrometres and marked with the ISO 1302 check-mark symbol.

A full section cuts the object completely with one cutting plane; the hatched area represents material actually cut, not surfaces behind the plane.

A half section removes one quarter of the object and is used for symmetric parts; the cut half and outside half are separated by a centre line, not a visible line.

A broken-out section is bounded by a thin irregular freehand or spline break line and exposes only a local feature such as a hole.

Hatching lines are thin, uniformly spaced at about 45°, and adjacent parts in an assembly are hatched in opposite directions or at different spacings.

Section lines, ribs, webs, shafts, bolts, nuts, and pins are not hatched when cut longitudinally; this convention avoids the appearance of solid thickness.

A cutting plane is shown by a chain thick line with arrows indicating viewing direction and identifying capital letters; the resulting view is labelled A–A.

An auxiliary view is projected perpendicular to an inclined surface from a primary view, giving true shape; a partial auxiliary shows only the inclined face.

Conventional breaks (S-break for round bars, zigzag for rectangular) shorten long uniform parts while retaining the true dimension value.

A detail drawing shows one part with all dimensions, tolerances, surface finish, material, and heat treatment needed for manufacture.

An assembly drawing shows the relationship and position of parts, with a parts list (item number, description, quantity, material, standard) and balloon leaders.

Balloon leaders terminate on the part with a dot or arrowhead and point to a circle containing the item number; they never cross each other.

Standard fasteners are drawn simplified: bolt heads and nuts are not shown in true projection, and threaded holes use the conventional major/minor diameter representation.

A thread is shown by a thick continuous line for the crest and a thin continuous line for the root, with the root line at 0.85 of the major diameter on external threads.

Running fits between moving parts, keyway and spline connections, and bearing seats require the appropriate ISO fit designation on the assembly.

Section views in assemblies distinguish adjacent parts by hatching direction and spacing; standard parts such as bolts and bearings are left unhatched.

Exploded isometric views with item balloons link assembly sequence to the parts list and are common in service documentation.

Plot scale 1:1 in paper space means one drawing unit equals one millimetre on paper; the viewport scale, not the plot scale, sets the drawing scale.

Plot style tables (CTB for colour-dependent, STB for named) map object colour or style to plotted lineweight and screening.

Lineweight display on screen is cosmetic; plotted lineweights come from the plot style or object lineweight property, typically 0.25 mm thin and 0.5 mm thick.

PDF output should embed fonts and use vector output; raster plotting at 300 dpi or lower degrades fine linework and small text.

A revision table records revision letter, date, description, and approver; revision clouds and triangles mark changed areas on the sheet.

Drawing numbers must be unique and traceable; ISO 7200 title block fields include legal owner, drawing number, revision index, and sheet number of total.

Plot preview verifies sheet margins, viewport clipping, and that no geometry falls outside the printable area before release.

Archiving requires the native file plus a neutral format (PDF/DXF) and a bill of materials so the drawing remains readable without the CAD system.