Making and Using Handtools


American Machinist Grinding Book by Fred H. Colvin and Frank A. Stanley, 1912

Choosing Grinding Wheels

We now come to the question of choosing suitable wheels for various materials and processes of machine grinding, and here comes the difficulty and want of a standard and of a universal method of grading.  Of the many firms engaged in the manufacture of grinding wheels there are probably no two which have a similar method of grading or designating the hardness of their wheels.  The Norton Company, which is probably the oldest in the field, uses the letter method, which may be said to be the simplest. 

Various other American companies use the letter method of grading to some extent, but all have individual ideas as to" what degree of hardness should constitute an M or medium-grade wheel.  Then we have firms both in America and on the continent of Europe which discard the letter method of grading or else use it in conjunction with numbers or fractions of numbers such as 2H, 1 1/2M and so on.  All this is bewildering to the user of wheels and constantly gets him into difficulty.  It very often happens that the maker and user are separated by long distances and the changing or obtaining of a suitable wheel means long delays and consequent loss.

The doubtful advantage to the wheelmaker of this state of chaos is that when a customer is educated to his special method of grading he will hesitate at trying his competitors' wares for fear of the trouble and confusion that may arise.  But there is another side to the question.  The writer knows of many instances where engineers are either conscious of the value of grinding processes or have ventured on the installation of a small plant, but the trouble with wheels has on the one hand made them afraid to commence the practice, and on the other it has either fallen into abeyance or not been carried out to the extent it seemed to deserve for the reasons stated.


Individual enterprise would seem to show that firms would come into line with a standard and international method of grading, as may be gathered from the following instance, which is not uncommon.  A firm of continental wheelmakers found that its sales were much restricted by its cabalistic method of grading when dealing with people who used the Norton wheel exclusively. 

As a simple matter of business they procured samples of most of the Norton wheels and compared them with their own for hardness.  The result was a circular issued to the firms interested, the substance of which was a comparative table showing how its wheel compared with the Norton.



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