Engineering Drawing

Thursday, 21 February 2013

Technical Lettering

Lettering is an impotent part of engineering drawing. It gives information regarding size, and instructions, in the form of notes and dimension. On a drawing, whole of the written information is always in the form of lettering. It is not hand written. Also, it may be added here, that Lettering is appropriate and correct words but not printing (Printing means production of printed material on a printing press).
  • Lettering
The writing of alphabets and numerals such as A, B, C, D…………………….Z and 1, 2, 3……………9, 0 respectively is called Lettering.
Mainly, there are two types of lettering most commonly used in engineering drawing viz. Gothic Lettering and Roman Lettering.
  • Classification Of Lettering
The lettering, in general, is classified in two categories :-
  1. Gethic Lettering
  2. Roman Lettering.
  • Gethic Lettering
Lettering having all the alphabets or numerals of uniform thickness is called Gothic Lettering.
  1. Vertical Gothic Lettering
  2. Italic or Inclined Gothic Lettering.
  • Single Stroke Vertical Gothic Lettering
These are vertical letter having thickness of each line of alphabet or numerals etc. Same as the single stroke of a pencil.Since Stroke means that the letter is written with one or more stems or curves and each made with single stroke.

  • Single Stroke Inclined Gothic Lettering
These are single stroke letter inclined at 75' to the Horizontal.

  • Double Stroke Vertical Gothic Lettering
Vertical letter drawn by double Stroke of pencil with uniform thickness between these strokes are called Double Stroke Vertical Gothic Lettering.

  • Double Stroke Inclined Gothic Lettering
Double stroke gothic when inclined at an angle of 75' is called Double Stroke Inclined Gothic Lettering.

  • Lower Case Vertical Single Stroke Gothic Lettering

Lower case vertical gothic lettering is shown along with its sizes. Which is quite self explanatory.

  • Lower Case Vertical Double Stroke Gothic Lettering
It is shown along with its size which is quite self explanatory.

  • Lower Case Inclined Single Stroke Gothic Lettering

It is shown with its sizes which is self explanatory.

  • Roman Lettering

The lettering in which all the letters are formed by thick and thin elements is called Roman Lettering.
It may be vertical or inclined or inclined. It can be written with a chisel pointed Pencil or D-3 type Speed Ball Pen.

  • Free Hand Lettering

The writing of alphabets without the use of drawing instruments and in free hand is called Free Hand Lettering.
It may be vertical or Inclined Gothic Lettering.

  • Mechanical Lettering
In Mechanical Lettering, standard uniform characters that are executed with a special pen held in a scriber and guided by a template. Mechanical lettering does not normally require the use of lettering guidelines. You will use mechanical lettering principally for title blocks and notes on drawings, marginal data for special maps, briefing charts, display charts, graphs, titles on photographs, signs, and any other time that clear, legible, standardized lettering is required. One of the most popular types of mechanical lettering sets is the LEROY lettering set.
The Mechanical Lettering is some times done using special type of device called a Pantograph.
PANTOGRAPH is basically a device consisting of four links which are pinned to each other in a parallelogram fashion. The links can move about the hinge. The lowermost link of the parallelogram is fixed to two rigid supports. One vertical link at one end is connected to a profile tracer which traces the profile of the letter to be drawn and the second vertical link and the other horizontal link are jointly connected to a pencil that draws the exact shape of the profile traced.

  • Height Of Lettering
The height "h" of the capital letter is taken as the base of dimensioning.
The main requirement of lettering on engineering drawing are legibility, uniformity, ease and rapidity in execution.
Both upright and inclined letter are suitable for general use. All letters should be capital, except where lower case letters are accepted internationally for abbreviations.
The recommended size of lettering is as under :-
    SIZE h, mm
    Drawing number in Title Block and letters denoting Cutting Plane Section
    10, 12
    Title of Drawing
    6, 8
    Sub-titles and Headings
    3, 4, 5, 6,
    Notes, such as Legends, Schedules, Material list, Dimensioning
    3, 4, 5
    Alteration, Enteries and Tolerances
    2, 3

    • Guide Lines
    The light thin lines drawn to obtain uniform and correct height of letters are called Guide Lines.
    Guide line should be drawn very light and thin, so that, they need not be erased after the lettering is finished. To erase guide lines after finishing the lettering is not easily possible. Guide line for capital and lower case lettering.

    •  How To Draw Graph For Lettering
    The letters are drawn in a graph. Before drawing the alphabets or numerals of 7:4, 5:4 or any other ratio, a graph is needed.

    • First of all take the height of  the lettering and draw two parallel horizontal lines.
    • Draw an inclined line at A and mark, 7 or 5 or as required number of vertical squares or rhombii, parts of any suitable size. Join B1 with B.
    • Draw parallel line to B1B from 1, 2, 3, 4, 5, 6 meeting the line AB at A1, A2, A3, A4, A5 and A6.
    • From A1, A2, A3, A4, A5 and A6 draw horizontal line.
    • From point B draw line at 45' to the horizontal.
    • Draw the vertical line for making lines for making squares and inclined line at an angle of 75' for making graph for inclined letters.

    Problems For Practice
    1. Rewrite the following in free hand vertical up right printing. Take height of letters = 10 mm. "GROW MORE FOOD"?
    2. Print free hand 10 mm height in capital up right letters the following :- DIFFERENT MATERIALS SHOULD BE INDICATED BY NOTES ON DRAWING?
    3. Write your name and the name of your institution in free hand single stroke vertical lettering, taking height of letters as 3 mm, 5 mm, 8 mm, 10 mm and 12 mm?
    4. Rewrite the following in free hand vertical upright and inclined lettering. I AM PROUD OF MY COUNTRY, take height of letters = 3 mm,4 mm,6 mm, 8 mm and 12 mm?
    5. Print the following neatly on the drawing sheet in vertical capital letters free hand only :- GOD HELPS THOSE WHO HELP THEMSELVES?
    6. Write alphabets A to Z and numerals 1 to 9 and "0" vertical upright and inclined lettering, free hand, single stroke. Height of letters = 3 mm, 45 mm, 6 mm, 8 mm,10 mm and 12 mm?
    7. Draw single stroke vertical capital letters of ratio 7 : 4 and 6 : 5, INDIAN STANDARD INSTITUTIONS?
    8. Print the single stroke vertical letters in height 28 mm in 7 : 4 ratio, BUY NATIONAL SAVING CERTIFICATES?
    9. Draw double stroke vertical lettering. A to Z ratio = 5 :4, Height =25 mm, ENGINEERING DRAWING

    Questions For Self Examination

    1. What is the purpose of lettering on a drawing sheet?
    2. What is the purpose of Guide Line in littering?
    3. What is the inclination of inclined lettering?
    4. What is the height of lettering for lower case lettering?
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