Drawing Office Rules.[1]
[1]Note.—A. W. Robinson, M.E., Montreal, must have all credit for these admirable rules and regulations. They bring into a single focus the whole science and art of mechanical drawing.
[1]Note.—A. W. Robinson, M.E., Montreal, must have all credit for these admirable rules and regulations. They bring into a single focus the whole science and art of mechanical drawing.
There are drawing offices where from ten to nearly one hundred people are busily employed in making new plans and sketches by the hundreds, and where thousands of completed drawings are filed for reference or for changes, as these are needed in the shop management.
To be introduced for the first time into such a company is a trial for the “new man” both of nerve and manners, and a test as well of skill; nothing helps more at such a time than an acquaintance with the rules and routine of the office, for the old saying holds good in a drawing office, of “doing in Rome as the Romans do.” The author of this book has felt this strangeness in a new position and so adds the following model-rules for the guidance of the student when first entering a regular position in an office where many are employed and where success depends upon a systematic ordering of the work in hand.
1. The standard size shall be 23 inches by 36 inches, subdivided into half, quarter and eighth sheets.
2. Full-size drawings shall be reserved, as far as possible, for general views and parts not capable of being shown on smaller sheets.
3. All shop detail shall, as far as possible, be shown on quarter and eighth sheets.
4. Detail drawings shall, as far as possible, classify the different kinds of works, such as castings, forgings, shafts, levers, piping, etc. Different kinds of work shall not be shown on the same detail drawing.
5. All shop drawings liable to repetition shall be traced and blue-printed. All temporary details, requiring only one copy, may be made on sketch sheets and press copied.
6. A shop drawing is to be considered as an order or instruction to the shop, and not merely as a statement or illustration. For this purpose it must convey clearly and distinctly all the information necessary to make the article.
7. Every dimension necessary to the execution of the work is to be clearly stated by figures on the drawing, so that no measurements need to be taken in the shop by scale. All measurements to be given with reference to the base or starting point from which the work should be laid out, and also with reference to center lines.
8. All figured dimensions on drawings to be plain, round vertical figures, not less than one-eighth inch high, and formed by a line of uniform width and sufficiently heavy to insure printing well. No thin, sloping, or doubtful figures, or diagonal-barred fractions will be tolerated. All figured dimensions below two feet to be expressed in inches.
9. All center lines to be alternate dot and dash in fine black line. All dimension lines to be double dot and dash, with a central space for the figure, and of such strength as to show on blue-print more faintly than lines of drawing. Lines of drawing to be bold and clearly defined in proportion to the scale, and may be shade-lined by making the right-hand and bottom lines heavier. No ornamental shading or other “frills” allowed on shop drawings.
10. Every drawing, whether whole or half-sheet, shall have the title, date, scale and number of the sheet stamped in lower right-hand corner, and the quarter and eighth sheets printed on top.
11. The name of the drawing, as given in the title, is invariably to consist of two divisions in one line separated by a hyphen. The first division is to state the general name of the thing or machine, andthe second name is to clearly designate the part or parts represented (or if a general view should so state). The wording of titles should be submitted to the chief engineer or head draughtsman for approval.
12. Each drawing shall bear the name of the draughtsman and examiner, the surname being used without initials.
13. Drawings of piping details shall be made in diagram form, using standard symbols.
14. All detail parts for standard or repetition work shall be shown unassembled as far as possible.
15. Detail shop drawings should state:
(a) The pattern number of every casting in plain figures of larger size than the dimension figures.
(b) The material of which the parts are made, using symbols as follows: C.I.—Cast iron. W.I.—Wrought iron. M.S.—Machinery steel. H.S.—Hammered steel. Bs.—Brass. Bbt.—Babbitt. Bz.—Bronze. C.R.S.—Cold rolled steel.
Other materials write full name.
(c) Finished surfaces will be indicated by “f” written on the line or surface to be finished. When not so marked it is understood that the part is to be left black or rough. In cases where finish might be presumed but not required, follow the figured dimensions by the word “cast,” if a casting, and “rough,” if a forging.
16. The following standards shall be strictly adhered to as given in the tables noted:
(1.) Table of standard diameters of shafting and key seats.
(2.) Table of standard stock sizes of rounds.
(3.) Table of standard stock sizes of flat steel.
(4.) Table of standard clearance fits.
(5.) Table of standard symbols for notation of riveting.
(6.) Table of standard symbols for pipe fittings.
Also such other standards as may be adopted from time to time.
17. Drawers and filing cases shall be numbered consecutively. Drawers shall contain 100 sheets each, and filing cases 200 sheets each, and to be fully indexed. Drawings shall be numbered by a number indicating both drawer number and serial number in the drawer—thus, 7,604 is the fourth sheet in drawer 76, etc.
18. Drawing numbers shall be checked off the index as required, and the index posted up in uniform handwriting by the clerk.
19. Standard size drawings shall be kept in drawers and quarter and eighth sheets in filing cases. All drawings shall be indexed by an index sheet kept in each drawer or case.
20. All drawings must be approved before being traced. When tracing is completed it will be given immediately to the chief draughtsman, who will have a preliminary print made and carefully checked, before being used.
21. All patterns shall bear the number of the drawing on which they are first detailed, followed by a serial letter, according to the number of patterns on the drawing.
22. Standard patterns used repeatedly and liable to be ordered from in repairs must not be changed. Other patterns may only be changed when absolutely necessary and by order. When so changed they will bear the original number and letter, followed by A for the first change, B for the second change, and so on thus: 4860 AB is the second change in pattern 4860 A.
23. Each draughtsman will be supplied with a sketch book by the company, in which he shall make all his notes, calculations and data referring to his work, and under no circumstances shall notes of value be made on loose sheets. Each entry should invariably be commenced with the subject and date, and fullnotes made of data on which the calculations were based, and the results obtained clearly stated. These books are to remain the property of the company.
24. Changes in drawings, sketches or order lists issued to the shop shall only be made when authorized by the chief engineer, or, in his absence, by the chief draughtsman, and when so authorized shall be made by the order clerk.
25. The names of all similar parts in order lists and drawings are to be uniform.
26. Tracings must be kept in safe, for blue-printing purposes only. Office copies of blue-prints must be used for references.
27. No drawing, print or photograph shall be taken from office without permission.
There are a great many different systems used in indexing drawings, most of which have some good points, but very few are sufficiently elastic to cover a wide field. A plan based upon the decimal system of notation is very simple, and, as there is no practical limit to the number of subdivisions, it can be expanded indefinitely. Following are the main outline features of the system as adapted to the needs of drawing offices belonging to large works.
The main division numbers, 000, 100, 200, 300, etc., are used respectively for all plans and general sheets referring to the division concerned. 100 includes general plans covering more than one department, and all small-scale plans with cross references to departments covered.
The class or tens divisions contain general drawings of the subdivisions, the subclasses or units divisions being limited to details only. Further subdivisions would probably be necessary in some cases. A card index with cross references and written by someone who knew what to do is an essential part of the system.
GEARING AND DESIGN
GearsFig. 263.
Fig. 263.