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The New Zealand Railways Magazine, Volume 2, Issue 10 (February 1, 1928)

Tool Steel Economy

Tool Steel Economy.

Much of the high speed steel used in machine shops is, to some extent, unavoidably wasted. This is due to what is known as the short end, or to that portion of the tool shank that is held in the tool box or post. To minimise this wastage, tipped and circular tools are becoming quite common in large machine shops. The tipped tool came into prominence during the War owing to the shortage of tungsten, vanadium, molybdenum and other rare alloys. The term “tipped” is self explanatory; it being merely a piece of high speed steel slightly larger than the profile or plan of the top face of the tool, which varies in page 37 thickness according to the size of the carbon steel shank. The tips are brazed on to carbon steel shanks with a specially prepared compound, and, after brazing, will withstand the high temperature required when hardened. In some instances the tips are welded on, but efficient brazing is simplest and preferable.

The circular tool is another type of tool but rather limited in its scope. It is fitted in a sort of tool holder, and consists of a piece of round high speed steel drilled through the centre and ground out concave on the face that gives the cutting edge the required rake. The clearance is determined by a slight taper, and the cutting face or profile is slightly larger than the base.

These tools require less frequent grinding than the ordinary tool, as they can be turned round in the tool holder until the entire circumference (which is the cutting edge) has broken down. For roughing and facing, this type of tool is extensively used in Great Britain and abroad. So general has become their use in large machine shops that a specially designed grinder can be purchased for grinding the concave top face which provides the rake for the cutting edge.

It will be readily seen that a set of standard tools embraces every tool that can advantageously be employed. Their selection and ultimate success in operation is one of the acid tests of machine shop organisation and control.

(To be continued.)