Course: THEA 272 Stagecraft
Introduction to Mechanical Drawing
Arthur Dirks
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Materials and equipment:

Drawing board* Tracing paper*
T-square* Pencils: .5mm H*, B; 3mm HB
Triangle: 45-45-90* Eraser: Soft red*
Triangle: 30-60-90* Compass
Architect’s scale* Variable triangle
Draftsman’s tape or dots* French curve(s)
Erasing shield Cleaning powder
Duster (draftsman’s brush or clean cloth) Various leads in lead holders and pointer are also useful.
*Required for exercises

 

Procedure and Notes:

-Light from the left (for right handers)

Mounting paper:

-Position paper on board with T-square. Tear 4 pieces of tape. Place one diagonally away from center of paper in upper left corner. Smooth paper diagonally with hand to lower right corner, align, and tape diagonally. Smooth away from center to upper right and tape, then to lower left.

Cleanliness:

-Wipe off and wash ruling instruments in mild detergent and warm water. Always work with clean hands. Never dust erasures with your hands!
-Plan your drawing to work from hardest pencil to softest, and to avoid passing instruments over final lines as much as possible. Suggestion:

  1. Lay in the drawing lightly with the hard pencil first (light H -or 2H).
  2. Then dimension, extension, section, trim, and other information lines (firm H).
  3. Then construction and other object shape lines (firm B) — verticals first, then diagonals, then horizontals, then templates.
  4. Then lettering (.3mm HB and .5mm B).
-When working on one specific section of a large drawing, especially at the top, shield the remainder with a piece of paper.
-Dust your drawing with cleaning powder if you are going to be doing a lot of work on it.

Using Instruments:

-Keep T-square braced tightly against the left edge of the board by rightward pressure with the heel of the left hand. Triangles may be held in alignment tightly with fingers.
-Never use T-square against more than one edge of the board.
-Triangles can be combined to provide all angles at 15-degree intervals, or use variable triangle.
-Triangles can be used for a straightedge, but never rule with the scale!
-Accuracy of measurement is critical, especially in scale: Sight directly from above the scale to measure, mark the point with the pencil.
-Irregular curves: Locate several points along the curve and sketch through them, or use a French curve to rule them.

Pencils:

-Lay-in and guide lines: H with a light hand, or harder (2H or 4H).
-Dimension and extension, and other information lines: Firm H
-Construction and object shape lines: Firm B
-Lettering, arrowheads, leaders, underlining and boxing: Firm H, HB, or .3mm HB

Lettering:

-Use vertical or inclined Gothic (not cursive, consistent case).
-Use guidelines drawn in lightly, or use graph paper under tracing paper.
-Rest hand on T-square or paper to shield drawing.
-Lettering normally runs parallel to T-square, not at odd angles.
-Common lettering problems:

Dimensions:

-The form for the dimension information is always x’-x"

-Dimension the view in which the object is most descriptively shown, then dimension other views as needed to complete the information.
-As much as possible, always place dimensions outside of view.
-Whenever possible, place all dimensions of the same axis on the same side of view.
-When several dimensions on one side span the same length, the smaller or shorter dimensions are placed nearest the object, with overall and longer dimensions farthest away from the object.
-When several dimensions on one side span the same length, the figures should be staggered for readability.
-Circles and arcs are dimensioned by radius, and the dimension is always shown where it lies, whether inside or outside the object.
-Angles are dimensioned by degrees in an arc swung from the vertex, but the dimensions of the legs of the angle and the opening are usually given also.
-Dimensions in very small scale spaces may be indicated with a leader.

Extension lines and leaders:

-Extension lines should not touch the drawn object.
-Leaders should be freehand lines with at least one obvious wave or curve to distinguish it from other working lines.
-Arrowheads should be formed with a three-move stroke, carefully pointing to exact points, to clearly distinguish leaders and dimensions from working lines.

Arrows

Title blocks:

-Always place title blocks in the same place, usually lower right corner. Readers need to expect where they will find the information.
-The block must contain the following information:

-The block may also contain information on the producing organization, the plate number, previous revisions, etc.
-Several forms are acceptable, but clarity and easy access to information is most important.

Notes:

-Notes about construction and procedures, legends, etc., should be collected in one area of the drawing plate as much as possible, and headed and/or boxed.
-Frequently, notes must be placed where a leader can indicate an area of the drawing for clarity.

Labels:

-All views must be separately labeled, usually in all-caps and double-underlined.
-Place below or beside the view so there is no confusion of what is labeled.
-If more than one scale is used on the plate, such as a larger scale for a detail, the block will contain the dominant scale and views with other scales are labeled, or each view must be labeled for scale.

Boxing:

-Traditionally, the drawing always has a border. It confines the drawing and indicates whether the print is a complete plate.
-Many draftsmen also box "Notes," "Legend," "Materials," and other non-pictorial parts of the plate, as well as the title block.


All original content protected by copyright © Arthur L. Dirks, Taunton, MA., 2005.