Sunday, December 4, 2011

Most Helpful Customer Reviews

The back cover claims that this is "The definitive guide to draughting to the latest ISO Standards, incorporating BS 8888". I cannot agree. This book seems to be a partial revision of a school or undergraduate drawing textbook. The authors might have achieved their objective if they had started from scratch. As it is, it would be better to call it a Rough Guide. It will be useful to beginners, but it is certainly not "definitive". The description of CAD systems in chapter 3 is heavily biased towards AutoCad, even when describing 3D programmes, in which they have never been dominant. The screenshot examples shown, over five pages, are taken as much from architecture as engineering, and are poorly reproduced. Captions are minimal, and the relevance to engineering of a dragonfly flying over a pond is hard to see. Two potentially informative screenshots of drawings in progress seem to have been printed in soot. The clarity and sharpness of a screen image is entirely lost. The authors appear to have shares in Mechsoft and the inclusion of two pages of AutoCad publicity material do little to advance the subject. The space would have been better used to illustrate the working methods of CAD programmes, particularly showing the difference between 2D and 3D work, and explaining the significance of Surface and Solid modelling, leading on to Hybrid programmes. The further use of 3D models for stress, heat flow, or fluid dynamics could have been illustrated. After pointing out on page 6 that the comma is to be the decimal marker, it is odd that the majority of drawings shown use the full stop, or point. The diameter symbol shown in the text does not agree with that shown in some illustrations, but the use is inconsistent. In both cases the symbol is incorrect. The section on drawing nuts and bolts continues a method which has been a poor approximation for more than fifty years, but makes no mention of using stencils, or CAD libraries, which would give an accurate representation. Chapters 20 to 23 reproduce the symbols for geometrical tolerancing as provided by AutoCad, including the errors. It would have been better to show them proportioned correctly to the standard. Several examples seem to have abandoned the correct use of line thickness. Chapter 26 shows welding symbols to BS 499. The authors should be aware that this was superseded in 1995 by BS EN 22553. Some explanation of the previous ways of working may be needed, but the emphasis should be on the current standard. The engineering diagrams in chapter 27 give a small selection of symbols to current standards, but far more space is given over to poor or non standard examples. The symbols used are inconsistent and no account has been taken of Reference Designations as specified in BS EN 61346. The section on Heating and Ventilation diagrams drifts into design techniques, which would be better covered in a Design textbook. The chapter on bearings similarly becomes a design manual, but the one illustration of the representation of bearings on a drawing is badly printed and incorrect. To add insult to injury, the text states that the drawing is wrong, but it has not been corrected! The final chapter deals with designing with adhesives. No examples of drawings showing assembly with adhesives are given, and we are completely in the world of design, not draughting, techniques. None of the finished drawings shown would be acceptable in my drawing office. The authors need to decide whether they are producing a Draughting or a Design Manual. The illustrations should ALL be up to date with the latest standards they claim to be presenting, and comply in every detail. They should represent the best of the draughtsman's art, not the typical products of those who have not kept up to date with the standards.

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