THE USE AND NEED OF THE MICROSCOPE IN 

 ENGINEERING WORKS. 



By S. Whyte, B.Sc. 



It is not necessary in these days to set out in detail the practical 

 help which is defived from the use of the microscope in engineering. 

 Everyone knows the great benefit it has been in controlling the question 

 of steel supplies and their heat treatment. By its means inherent 

 defects in the steel are discovered. Troubles may arise at the steel 

 works through bad ingot pouring, and any pipes or seams which occur 

 in the portion of the ingot which is used finds its way into the billets 

 and bars. Also, faults may arise in the forging or stamping of the 

 steel w^hich are difficult to detect without a microscope. For finislied 

 parts the microscope is almost essential in working out and standard- 

 ising the best methods of heat-treatment, and in the event of failures 

 of these parts in service, in helping to discover the processes by which 

 these failures originate and develop. This by no means exhausts the- 

 list of uses to which the microscope can be applied in examination of 

 metals for engineering works, as the properties of castings — both 

 ferrous and non-ferrous — can be co-related with their various micro- 

 constituents and their distribution or crystalline arrangement. 



The writer does not propose dealing in detail with the various 

 branches in which, from his own experience, he has found the micro- 

 scope to be of great value. It is sufficient to say in passing that the 

 microscope ought to be, and will be in the near future, an essential 

 part of the average engine'ering works equipment, especially where the 

 products being manufactured are subjected to live loads, and on which 

 the safety of life depends. 



The purposes for which the microscope is used, as outlined above, 

 are three-fold, and endless examples could be given. 



First, in the examination of raw material, as supplied by the steel 

 makers and stampers. It is not enough in all cases to buy merely to 

 chemical specifications, as two pieces giving the same analysis may 

 differ in their usefulness. One may be sound, while the other shows 

 segregations and results of ingot piping. Faults such as these, how- 

 ever, are becoming rare, as the improvements in recent years, specially 

 in regard to ingot casting, have done much to eliminate them. It is, 

 however, still important that samples of new types of stampings, as 

 they come from the makers, should be examined for incipient cracks 

 or " laps " of oxide driven into the material, specially when the 

 stampings are intricate, and the steels used are alloy steels. It is 

 impossible to tell, other than by the microscope, that some of these 

 flaws exist, and it will help the stamper to correct his dies, and will 

 save time and expense and the possibility of subsequent failures from 

 this cause, if defects can be detected from the beginning. Micro. No. I. 

 is an example of this type of defect. 



Secondly, and what is more important from the engineer's ])oint of 

 "'iew, the microscoj^e is a great help in arriving at the' best heat-treat- 

 ment temperatures for his steel. It is absurd to buy expensive high- 

 grade alloy steels, and not use every means of obtaining the best results 

 from them. It is equally extravagant to buy high-speed steel for tools 



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