Emery grinding machinery

This little handbook has been compiled by the author in the hope that it may prove of service to Manufacturers engaged in Mechanical and Metal-working Industries, to Tool-makers and Machinists, and to Students and Workshop Apprentices generally. The work lays no claim to originality in regard to the methods discussed, neither does it pretend to have exhausted the subjects to which it is devoted.

The author's sole aim has been to produce a handbook of workshop practice, and his endeavour has been to place descriptions of the machinery employed, and the methods adopted for grinding, sharpening and polishing metals by means of the emery wheel, in the manufacture of articles of commercial utility. He has had no interest, direct or indirect, in extending the sale of any of the machines described: where certain firms are mentioned by name, this has been done in order to describe leading types, and it is not in any way intended to suggest that such firms are the only makers of the tools under discussion. Conditions in America differ greatly from those prevailing in our own country, and American manufacturers have developed and specialized in certain directions, to an extent of which we have comparatively little conception in our own country. This specialization has nowhere had greater results than in machine-tool manufacture, and numerous machines of this description have found their way into British workshops, usually with the happiest results as regards economy and efficiency. This has led to an erroneous impression, which has been fastened and encouraged in our own technical and daily press, that British manufacturers and British methods have fallen far behind in the race. As regards grinding machinery this notion is certainly far from the truth, and for many years past machines of purely British manufacture have been procurable which compare favourably with those of the best American makers.

Amongst the American firms which have placed Emery Grinding Machines upon the market are — the Brown & Sharp Mfg. Co., the pioneers of the Universal Grinding Machine, and two other firms who have given considerable time and attention to special grinding tools, namely, the Pratt & Whitney Co., and the Norton Emery Wheel Co.

CHAPTER I.
Introduction - A Review of Ancient and Modern Methods - The Necessity of Sharp Tools - The Natural Grindstone - The Mechanical Method

CHAPTER II.
Emery Wheels - Composition of Emery Wheel - Selection of suitable Emery Wheel - Advantage of Wet Grinding- Grades of Emery Wheels

CHAPTER III.
Mounting Emery Wheels - Care in Mounting the Wheel - Suitable Form of Flange - Points concerning Safe Working, Accidents - Table of Emery Wheel- Speeds

CHAPTER IV.
Emery Rings and Cylinders - Dressing the Emery Wheel - Use of the Diamond Turning Tool - Emery Wheel Dressers - Speed for Truing Emery Wheels

CHAPTER V.
Conditions to ensure Efficient Working - Amount of Surface Contact-Heating due to Area of Contact - Drill Grinding - Imperfections of the Hand-ground Drill - Angle of Clearance on Drill - Variation of Drill Clearance - Points concerning Drill Grinding - Setting a Drill Grinder

CHAPTER VI.
Description of the Leading Types of Machines - Automatic Grinding Machines - Engineer's Tool Grinding - Horizontal Emery Grinder - Automatic Knife Grinder - Automatic Surface Grinding - Surfacing Engine Piston - Rings - Rifling Chilled Rollers - Adjustable Carriage and Guide Bar - Adjusting the Roller - Turning, Grinding and Rifling Lathe - Rifling Flour Mill Rolls- Centring the Roller for Re-grinding

CHAPTER VII.
Concave and Convex Grinding- Grinding the Concave- Grinding the Convex - Grinding Rolls Internally - Long Cylindrical Work - Grinding a Piston-rod - Comparison between Old and New Methods

CHAPTER VIII.
Cup and Cone Grinding Machines - Combinations for Internal and External Work - Double Cup Grinding - Examples of Automatic Cone Grinding - Ordinary Milling Cutters - Reamers and End Mills - Examples of Gang Cutters - Special Formed Milling Cutters - Form of Teeth for Cutters - Strength of Saw Teeth – General Examples of Cutter Grinding - Points concerning Metal Saws - Saw-tooth compared with a Turning- tool - Sharpening Cutter- teeth without Waste - Inaccuracies in Grinding Clearance

CHAPTER IX.
Multiple Grinding- Grinding Metal Links on End and Back Edges- Single and Multiple Grinding compared - Threading Machine for Multiple Grinding - Explanation of Threading Machine

CHAPTER X.
Universal Grinding Machines and Cutter Grinding Machines - Misapplied Terms for Special Machines - Shafts, Tapers and similar work - Sharpening Reamers and End Mills - Difficulties in adjusting the Head - Alignment of the Headstocks- Position of Head for External work- Effect of the Belt Pull- The “Guest” Cutter Grinder - Eccentric Lock for Swivel Table - Sharpening Cutters on Face and Edge of Emery Wheel - Diagrams explaining Methods of Sharpening Cutters on "Guest" Cutter Grinder - Typical American Cutter Grinders - Setting an American Cutter Grinder - Springing of American Machines - Weak Points in American Design - British and American Machines compared

CHAPTER XI.
“Ward” Universal Cutter Grinder- Combined Cutter Grinder and Twist Drill Grinder - Sharpening Spiral Cutter, Involute Cutter, Taper Milling Cutter - Grinding Press Tools - Design of Press Tool Grinder - Operating on Bevel Edge of Die, Inside Drawing Die, Sizing a Drawing Punch, On Face of Cutting Punch and Die - Surfacing Press Cutting Tools - Construction of the "Ward" Universal Cylindrical Grinder - Arrangement of the Countershafts

CHAPTER XII.
Correcting Lathe Centres - Rectifying Dynamo Commutators - Emery Roller Machines - Emery Band Machines- Cleaning Teeth of Cast Iron Wheels - Automatic Saw Sharpening – “Schmaltz” Machine sharpening Circular and Frame Saws, for wood - Saws for Hot and Cold Metal work

CHAPTER XIII.
Polishing- Preparing the Emery Bob - Re-dressing the Emery Bob - Polishing Inside and Outside Metal Cups - The Use of Emery, Oil, and Wood Strip Polishing Steel Washers - Scouring Steel Roller

It is questionable if any other class of machinery applied to uses in engineering and machine-tool workshops has developed so rapidly, or their use become so universal during recent years, as emery grinding machines.

Judging from the great number of specialities in this line which have been imported into the United Kingdom from America, there seems to be little doubt that for many years the American engineers have taken an extreme and intelligent interest in matters connected with the improving and perfecting of these machines. In numerous British engineering manufacturing establishments every known improvement in this direction has been utilized in actual practice, and for ordinary work the emery wheel has to all intents and purposes superseded planing and shaping machines in modern engineering workshops. The general manufacturer in the various branches of metal-working and allied trades unfortunately does not at present appear to have taken full advantage of the advantages offered by the use of the emery wheel.

The extensive introduction of milling and profiling machinery has created a field for special (grinding machines required to sharpen the various forms of cutters used in such processes. This demand has had the effect of raising these machines into undue prominence.

It is interesting, however, to observe that at the present time the British engineer is actually manufacturing his own specialities in grinding machinery, and that several of these have such meritorious features in their design as to render them superior to some of the American imported machines. This certainly indicates that when there is a sufficient demand the British engineer is ever ready to turn his attention to new fields.

The following particulars are compiled from stray notes collected from various sources and at various times. They are published in the hope that they may prove useful as a small book of reference to students, engineers, toolmakers and manufacturers who are interested in the emery wheel, but who may not be able to spare the time necessary to search for the information which is at present scattered throughout numerous technical publications and periodicals.

A review of Ancient and Modern Methods.

The cutting edges of hardened tools are recovered and maintained by methods of grinding as diverse as are their shapes and the purposes for which the tools themselves are employed. And the classes of work that are included under the heading of press-work are so numerous, that it is quite as difficult to arrange any special or definite course to be followed in the maintenance of these classes of tools, as it is to define any special course to pursue in their actual production.

The necessity of keeping the cutting edges of tools sharp and in good order for the production of the best result is evident when a careful observation is made of the action of the tools used for cutting sheet metals, such as a cutting punch and bed, or a set of slitting shears.

The steels from which all such tools are made are of the same quality, that is, they have the same percentage of carbon and are soft enough to be readily worked into the shape required; any modification of hardness subsequently required is brought about by hardening and tempering.

When blanks are cut from thin sheet metals with a punch and bed, not only must the punch fit tightly and perfectly in the bed, but the cutting edges must be kept perfectly sharp; in such cases it is usual to make the steel of the cutting bed rather hard, and that of the punch softer, by temperid the former to a yellow and the latter to a blue colour.

This allows of the face of the punch being hammered out, smoothed over with a fine cut steel file and subsequently ground on an emery wheel ; as also of the punch being forced into the bed so as to make it resume its original shape and fit the bed perfectly. As this process has to be very often, the punches are worn away much more rapidly than the bed, which retains its shape for a much longer time, and seldom requires sharpening.

When thicker sheet metal is operated on, the punch and bed are tempered to nearly the same hardness; hence both these tools then require occasional grinding in order to make their cutting edge perfectly sharp and square. In the smaller establishments this is usually affected by holding the face of the punch or bed against a grinder or natural grinding stone (fig. 1), or an emery wheel.

The punch or bed is grasped in the workman's hand and pressed up against the side of the stone or emery wheel in the manner shown at fig. 2; then the tool face is tested to see if it is flat and square by trying with an ordinary steel try square (fig. 3). As can readily be understood, the experienced workman will recover the edges in far less time and with less waste of material than the inexperienced. For instance, in the hands of the latter the first result may be as shown in fig. 3; while subsequent ones may be as represented in fip. 4, 5 and 6, so that by the time the tools have acquired the perfect form (fig. 6) much material has been wasted.

In ordinary practice, indeed, the loss of material undergone by the tools when actually cutting the blanks is far less than the loss caused by regrinding and sharpening them; hence their wear is mainly due to the latter operations.

The trouble that is experienced in grinding the face of a punch flat may be largely overcome by recessing the punch face as shown at A, fig. 7, as this makes it less liable to the shape seen at fig. 5. Until comparatively recent years the natural grindstone practically the only available means by which the press tools could be recovered. It is, however, in many workshops now rapidly being replaced by the emery and corundum wheel, and there is good reason to believe that in time the natural grindstone will cease to be used for press tools. The Special forms of emery wheel grinding machinery may now be seen in many workshops, their use having been found to be of the greatest possible advantage. The well known twist drill grinder and the universal  grinding machine are used for sharpening milling cutters of all shapes, a8 also taps, reamers, etc; while special grinding machines deal with cylindrical work, such as engine piston-rods, rollers and bushes, chilled rolls, cutter holes, male and female gauges, etc. ; surface grinders and machines which deal with lathe and shaping tools, turning and boring tools ; and others.

As mechanical should always be preferred to manual tool grinding, the following brief sketch of the leading types of grinding machinery will suffice to indicate the adaptability, superior efficiency and economy of the emery wheel grinding machine, even in the hands of an unskilled mechanic.

The tools used in making the interchangeable metallic parts of such mechanical arrangements as clocks, watches, musical boxes, typewriters, locks, electrical instruments, etc., in which accuracy is essential to their efficiency, and of which large quantities are required, must themselves have a high degree of excellence. There is a good field for the application of high grade machinery both for producing and maintaining the tools.

There are other classes of work - shovels, stove trimmings, kitchen utensils, hardware, coal hods, etc. - which, on account of the rough quality of the finished article or the comparatively small quantities of work required from the set of tools, do not warrant special machinery being introduced for grinding by mechanical means; tool-sharpening then is done by the readiest available means.


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