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The New Zealand Railways Magazine, Volume 2, Issue 11 (March 1, 1928)

Tools of Steel. — (Part VI.)

page 24

Tools of Steel.
(Part VI.)

“A Man of the Windmill Species, that Grinds always.”

Workshop Precision Grinding.

The cylindrical, plane, or surface grinding machine is the product of comparatively recent years. By many tradesmen it is regarded as a specialised machine for repetition work, or for jobs that are too hard to be machined or filed in the ordinary way.

The grinding machine, however, is essentially a finishing machine for a great variety of work. Its speed and the accuracy with which it functions cannot be denied. It is doubtful if there is a turner or machinist anywhere (no matter how skilled), who, using a lathe or other machine, can finish work as quickly and as accurately thereon as the same work can be done on a grinding machine when correctly handled.

Interior of Invercargill Workshops. Top: A corner of the machine and fitting shop. Bottom: Improved tool rack.

Interior of Invercargill Workshops.
Top: A corner of the machine and fitting shop. Bottom: Improved tool rack.

Although a grinding machine is a precision tool, it nevertheless requires less skill to operate (when employed on accurate work) than the lathe, milling machine, or planing machine, etc. As a finishing machine it has dispensed with most of the skill demanded of the old time craftsman (the use of file and emery cloth) for finishing and polishing work to fine dimensions.

If a workshop foreman twenty years ago had requested his best turner to turn a dozen piston (or valve) rods, all to a given size, and, at the same time have stipulated that there must not be more than .0015 of an inch variation in the finished size of the rods so turned, such a turner would have been perplexed and worried as to whether or not a request of the kind could actually be carried out.

In modern workshop practice, however, measurements much finer than the above are quite common.

The Grinding Method.

It makes very little difference upon what class of work a workman may be engaged, whether it be work demanding the greatest accuracy and fine finish (or vice versa), or that the material to be worked be of hard or soft metal, cast or forged,—the grinding machine is the all round finishing machine tool. Just as high speed steel has increased production by displacing carbon steel in many processes, so has the grinding machine increased production by displacing the file, the scraper, the lap and emery cloth for finishing.

It is a mistake to regard the grinding mamachine as essentially a repetition machine. This is entirely erroneous. Whilst the said machine does show to advantage on repetition work (owing to its automatic trip and its all but fool proof accurate feed control) it nevertheless has a much wider scope of usefulness. In the case of the individual article for instance,—after the size is known and a trial cut has been made—the feed control eliminates the problem of human error and reduces the said article to the pre-determined size far more quickly and accurately than any other machine.

The grinding machine has, in the space of a few years, became so universally used that the page 25 Churchill Machine Tool Co., Ltd., manufactures grinding machines of various sizes weighing anything from 20lbs. up to 60 tons. So splendidly are these machines designed and balanced that, weight for weight, there is no other machine that requires as little manual exertion to operate.

Lest there should be any misunderstanding I should like to observe in passing that grinding is a distinct cutting process and is subject to much the same conditions as are those of the lathe or planing machine. A grinding wheel can be too sharp for certain work or too dull; it can be too soft, or too hard. Just as an ordinary tool with only one cutting edge will remove a chip of metal proportional to its strength, so does the grinding wheel with its multiple cutting edges function similarly. The metal removed by a grinding wheel when placed under a microscope bears a striking resemblance to the chips removed by a lathe or similar tool.

Lathe v. Grinding Machine.

The re-turning of an axle or the re-boring of a cylinder involves the removing of more metal from either than would be necessary if the same operations were done on a grinding machine. This is due to the fact that a worn axle or cylinder develops a hard skin, which necessitates that before any progress can be made with the tool, the turner must take a cut sufficiently deep to get under the skin. Afterwards a second (or finishing) cut is necessary.

The grinding machine functions equally well on hard or soft metals, therefore, when re-grinding an axle or cylinder witness marks may be left in, and only the bare minimum of metal removed. This produces a smoother and truer surface, adds considerably to the life of the parts that have been thus treated and creates a big saving in regard to renewals, etc. Furthermore, the grinding method has proved conclusively that, re-grinding, apart from these advantages, is also quicker than re-turning.

Competition and Grinding.

This is a competitive age, an age that right or wrong casts out the unfit. The machine tool manufacturers and the motor car industry live and flourish under the fiercest conditions known to this said system. Both of these important and exact branches of engineering have adopted successfully the grinding method. This is no mere fashion of the age, but the recognition that the grinding machine has been found indispensable where quantity, quality, and sound economics, govern the industrial and social programme. But for the grinding machine, says a well known American Trade Journal it would cost as much to produce a Ford car as it does a Rolls Royce.

(To be continued.)

New Methods at East Town Workshops. One of the four special planing machines recently introduced into the Workshops, for the manufacture of frogs, Switches and scissors crossings. These machines are electrically driven.

New Methods at East Town Workshops.
One of the four special planing machines recently introduced into the Workshops, for the manufacture of frogs, Switches and scissors crossings. These machines are electrically driven.