Pens
Traditional and typical pens used for technical drawing are pencils and technical pens. Pencils in use are usually mechanical pencils with a standard lead thickness. General line widths are 0.18 mm, 0.25 mm, 0.5 mm and 0.7 mm. Hardness varies usually from HB to 2H. Softer lead gives a better contrast, but harder lead gives more accurate track. Bad contrast of the lead track in general is problematic at photocopying, but new scanning copy techniques have improved the final result. Paper or plastic surfaces do require their own lead types.
Drawing board
The drawing board is an essential tool. Paper will be attached and kept straight and still, so that the drawing can be done with accuracy. Generally, different kind of assistance rulers are used in drawing. The drawing board is usually mounted to a floor pedestal in which the board turns to a different position, and also its height can be adjustable. Smaller drawing boards are produced for table-top use. In the 18th and 19th centuries, drawing paper was dampened and then its edges glued to the drawing board. After drying the paper would be flat and smooth. The completed drawing was cut free. Paper could also be secured to the drawing board with pins. More recent practice is to use self-adhesive tape to secure paper to the board. Some drawing boards are magnetized, allowing paper to be held down by long steel strips. Boards used for overlay drafting or animation may include registration pins or peg bars to ensure alignment of multiple layers of drawing media.
T-square
A T-square is a straightedge which uses the edge of the drawing board as a support. It is used with the drafting board to draw horizontal lines and to align other drawing instruments. Wood, metal, or plastic triangles with 30 and 60 degree angles or with two 45 degree angles are used to speed drawing of lines at these commonly used angles. Also in use are a continuously adjustable 0-90 degrees protractor. An alternative to the T-square is the parallel bar which is permanently attached to the drawing board. It has a set of cables and pulleys to allow it to be positioned anywhere on the drawing surface while still remaining parallel to the bottom of the board. The drafting machine replaces the T-square and triangles.
Drafting Machine
A drafting machine is a device which is mounted to the drawing board. It has rulers whose angles can be precisely adjusted with a controlling mechanism. There are two main types of apparatus: an arm-type parallelogram apparatus based on a hinged arm; and a track-type apparatus which moves on a rail mounted to the top of the drawing board. The accuracy of the arm type apparatus is better in the middle of the board, decreasing towards the edges, whereas a track machine has a constant accuracy over the whole board. The drawing head of a track-type drafting machine slides on bearings in a vertical rail, which in turn is moved along a horizontal, top-mounted rail. Both apparatus types have an adjustable drawing-head with rules attached to a protractor scale so that the angle of the rules may be adjusted. A drafting machine allows easy drawing of parallel lines over the paper. The adjustable angle between the rulers allows the lines to be drawn in varying accurate angles. Rulers may also be used as a support for separate special rulers and letter templates. The rules are replaceable and they can be for example scale-rules. Drawing apparatus has evolved from a drawing board mounted parallel ruler and a pantograph, which is a device used for copying objects in an adjustable ratio of sizes.
French Curves
French Curves are made of wood, plastic or celluloid. Some set squares also have these curves cut in the middle. French curves are used for drawing curves which cannot be drawn with a compass. Faint free hand curve is first drawn through the known points. Longest possible curves exactly coinciding with the free hand curves are then found out from the French Curves. Finally, neat continuous curve is drawn with the aid of the French Curves.
Rulers
Rulers used in technical drawing are usually made of polystyrene. Rulers come in two types according to the design of their edge. Straight edge can be used with lead and felt pens, whereas when technical pen is used the edge must be grooved to prevent the spread of the ink.
Compass
The compass is used for drawing circles or arc segments of circles. One form has two straight legs joined by a hinge; one leg has a sharp pivot point and the other has a holder for a technical pen or pencil. Another form, the beam compass, has the pivot point and pen holder joined by a bar, useful when drawing very large radius arcs. Often a circle template is used instead of a compass when predefined circle sizes are required.
Templates
Templates contain pre-dimensioned holes in the right scale to accurately draw a symbol or sign. Letter templates will deliver the text, as well number as letter characters. Diagrams are usually of a standard letter shape and size to conform to standards of encodings (e.g. DIN or ANSI). For example in Finland the series used is 1.8 mm, 2.5 mm, 3.5 mm, 5.0 mm and 7.0 mm. Except for the very biggest ones, the templates are suitable for only technical pen drawing. For drawing circles and circle-arcs, circle templates are used, containing a suitable set of holes in certain dimensions, with suitable sized holes in them. Models are also available for other geometric shapes such as squares and for drawing ellipses, as well as many specialized varieties for other purposes.