A text-book of elementary foundry practice : for the use of students in colleges and secondary schools

Front matter

Copyright W.

COPYRIGHT DEPOSIT

A TEXT-BOOK

Preface

In offering this book to the public, the author would state that upon taking up the work of teaching foundry practice to boys in secondary schools, he was confronted with the great lack of literature on the subject, there being very little of an elementary character suitable for use as a text or a reference work.

He has therefore tried to select matter — not too difficult for high school pupils and at the same time sufficiently advanced for the college student — such as will bring out the largest number of principles used in the molder's art; and he has endeavored to make everything so plain and practical that even without the direction of an instructor the student can put the patterns into the sand and achieve good results.

The patterns chosen may be easily obtained ; moreover, as each pattern brings out one or more distinct principles, a student who has completed this course ought to be able, without further instruction, to produce satisfactory results with any reasonable pattern. Several supplementary exercises should be given to test the grasp of the principles. The author is fully aware that a great deal of work found in ordinary foundries and involving many principles has been omitted, but this has been done only after due consideration of all things involved and discussion with able educators.

It is hoped that the ideas herein presented will be of as much value to others engaged in the profession as they have been to the author. He freely acknowledges his indebtedness to various books and periodicals for ideas received therefrom.

VI PREFACE

He is especially indebted to the authors of the following books : American Foundry Practice by West, Foundry Practice by Tate and Stone, Foundry Work by Stimpson, General Foundry Practice by McWilliams and Longair, Pattern Making and Foundry Practice by L. H. Hand, and Pattern Making hy S. E. Ritchey.

Contents

PAGE

Introduction xi

Definition xi

Foundry Practice — Green-sand Molding — Core Making — Dry-sand

Molding — Loam Work ......... xi

Chapter I

Sands — Molding Sands (Light, Medium, Heavy) — Free Sands — Core Sands — Parting Sands — Facing Sands — Loam — Black Loam — Facings — Sea Coal — Graphite — Charcoal — Coke — Talc — Blacking — Fire Clay — Clay Wash — Core Binders . . . . i

Chapter II

Flasks (Ordinary. Snap) — Slip Case — Moldboard — Bottom Board — Riddle — Shovel — Rammers — Straightedge — Trowels — Slicks — Lifters — Bellows — Sprue Plug — Corner Slicks — Swabs and Sponges — Draw Spikes — Draw Plate — Vent Rods — Gater — Weight (pouring) — Clamps — Wedges — Pinch Bars — Tool Box 9

CHAPTER III Principles of Molding

Preparing Sand (Introduction of new sand or facing, Tempering) — Ramming (Drag, Cope) — Auxiliary (Crossbars, Gaggers, Soldiers, Nails) — Venting — Gating — Risers — Skimming Gates — Shrinkage Heads — Patching — Stopping Off 19

CHAPTER IV Molding Exercises without Core

Ex. I. Rectangular Block — Ex. 2. Cylinder (Solid Pattern). Method No. I — Ex. 3. Cylinder (Solid Pattern). Method No. 2 — Ex. 4. Cylinder (Split Pattern) — Ex. 5. Application of Principle in Ex. 2 and Ex. 3 33

Viii CONTENTS

CHAPTER V Matches

PAGE

Definition — Ex. 6. Green-sand Match — Ex. 7. Oil Match — Ex. 8.

Plaster of Paris Match 41

CHAPTER VI Molding Exercises with Green-sand Cores

Ex. 9. Simple Green Core — Ex. 10. Grooved Pulley (Two-part Flask)

— Ex. II. Grooved Pulley (Three-part Flask) — Ex. 12. Column Base (Three-part Flask) 44

CHAPTER VII Dry Cores Cores — Binders (Flour, Rosin, Linseed Oil, Glue) — Molasses Water

— Clay Wash — Manufactured Binders — Core Materials other than Binders (Wire, Gas Pipe, Cinders, Wax, Charcoal, and Graphite)

— Composition — Making (Tools, Mixing, Baking, Oven) — Finishing ........•••• 49

Chapter VIII

Venting Cores — Setting Cores (held by Prints only; held by other Means) — Ex. 13. Simple Straight Dry Core — Ex. 14. Setting Bolt Hole Core and Core below the Surface (pocket core) — Ex. 15. Balanced Core — Ex. 16. Setting Core below the Surface (by Stopping Off) — Ex. 17. Segment Core — Ex. 18. Hollow Core — Chaplets— Setting Chaplets — Ex. 19. Nailed Core — Ex. 20. Nailing Core to Bottom Board — Ex. 21. Hanging Core — Ex. 22. Anchoring Core with Chaplets — Ex. 23. Anchoring Core with Chaplets (Chaplets extending through Cope) 55

Chapter IX

Gated Patterns— Ex. 24. Gated Pattern (Plain Moldboard) — Ex. 25. Gated Pattern (Match Board) — Irregular Parting — Ex. 26. Mold with Irregular Parting — Pattern with Removable Parts — Ex. 27. Loose Piece Pattern — Ex. 28. Removable Boss — Draw-rim Pulley — Ex. 29. Draw-rim Pulley (with Hollow Core for Arms) — Ex. 30. Draw-rim Pulley (with Lifting Ring) — Sweeping or Striking Cores — Ex.31. Strike Core 72

CONTENTS IX

CHAPTER X Open Molding, Sweep and Strike Work PAGE

Ex.32. Open Mold — Sweep Work — Ex.33. Sweep Mold — Strike

Work — Ex. 34. Strike Work 81

CHAPTER XI Dry-sand Molding

Description — Ramming — Venting — Finishing — Ex. 35. Dry -sand

Mold 85

CHAPTER XII Cupola Practice or Melting

Cupola — Ladle — Tools — Bott Clay — Preparing and Operating the Cupola — Pouring — Poured Short — Blowholes — Cold Shuts — Scabs — Sand Holes — Swells — Shrinkage Cracks — Warping — Fuel 87

CHAPTER XIII Cleaning Castings

Rattler — Pickling — Sand Blast 95

CHAPTER XIV Chilled and Malleable Castings

Chilled Castings — Action — Placing Chill — Coating Chills — Gates —

Depths of Chill — Mixture — Malleable Cast Iron — Process . . 97

CHAPTER XV Brass Molding

DiiTerence between Brass and Iron Molding — Materials — Flask — Clamps — Spill Trough — Drying — Ex. 36. Ornamental Plaque — Ex. 37. Brass Molding with Core — Cleaning — Melting — Brass Furnace — Operation — Brass and Bronze — To make a Certain Composition ........... 100

Glossary 107

Appendix — Devoted to Table and Receipts useful in the Foundry . 113 Index . . 119

INTRODUCTORY

Definition. — Foundry practice consists in making sand molds and filling them with metal in a liquid form, which hardens into what are called castings.

These castings may be placed into three classes, each having distinct physical properties ; such as Strength, Toughness, Durability, etc. These are, —

Gray Iron

f Brass Bronze Bell Metal, etc.

Mild Steel.i

With special treatment in the mold or after removal therefrom, two other forms of iron castings can be obtained ; namely. Chilled and Malleable.

Molding is the making of the molds and the cores used in these molds, and is divided into four branches :

1. Green-sand Work

2. Core Work

3. Dry-sand Work

4. Loam Work ^

Green-sand Molding. — This consists in ramming moistened molding sand about a pattern in a flask, the impression of the pattern being retained in the sand when it is withdrawn. This impression is then filled with molten metal, and the casting results. Because of its cheapness and quickness, green-sand molding is the most common method of making castings.

1 Not treated in this work.

xii INTRODUCTORY

Core Making. — This consists in shaping by means of a core box (wooden mold) a mixture of core sand and some binding material, and baking the mixture. Cores are used to form holes or cavities in castings.

Dry-sand Molding. — Dry-sand molding consists in making an impression of the pattern by packing a core-sand mixture about it in a flask, and baking the sand after removing the pattern. The baking drives off all of the moisture, leaving a hard, clean surface. It is used where rush or bulk of metal would be likely to spoil a green-sand mold.

Loam Work. — This consists in building a mold of bricks on which a facing of mortar is placed. This mortar is shaped by means of sweeps or patterns, after which the entire mold is baked. Loam work is used for very heavy classes of work, or where so few pieces are required that it would not pay to make ordinary patterns.

A TEXT-BOOK

OF

A TEXT-BOOK OF ELEMENTARY FOUNDRY PRACTICE

CHAPTER I The materials used in the foundry for making molds are

Sands

Loam Facings

Miscellaneous

[ Light

Molding j Medium

[ Heavy

^ , f Sharp or river

Free sands '

[ Beach sand f Graphite Charcoal Sea coal

I Talc Fire clay

Parting dust

Core binders

Sand

Burnt sand

Charcoal

Manufactured preparations

River

Beach Flour Rosin Linseed oil Glue, etc.

SANDS

Sands are the result of the breaking up of rocks by weather and the action of water. Rain water lodged in the cracks and crevices of rocks, when frozen in cold weather, will cause parts of the rock to break off. These parts are carried by the rush of rain water down the mountain sides to the rivers, where they are rolled and broken and worn away, to the size we call sand. As the current of the river grows less rapid, its carrying power becomes less. The heavier grains settle first, so that we find gravel or coarse sand, then fine sand, and next a sand and clay mixture, with the clay gradually increasing until the sand disappears and clay only is found.

Our rocks have very complex compositions. Since our sand contains nearly all of the elements of the rock, it is also quite complex.

Molding Sands

The material which is used in making the molds in the foundry must be porous enough to allow the escape of the air and the steam and gas generated by the heat of the metal poured, and yet at the same time compact enough to hold the liquid metal. It must be refractory, — that is, able to stand very high temperature, — and it must not produce any chemical action with the metal at this temperature. It must be readily removed from the casting, and leave a clean, smooth surface.

Sand most nearly fulfills these conditions, as it has no chemical action with hot iron ; it allows the gases to pass off readily, and at the same time compacts hard enough to retain the molten metal and conform to the pattern.

Selection. — It is very important that a proper sand be selected for the class of work to be done, for upon this the success of the casting largely depends.

Molding sand used in making molds for cast iron is composed chiefly of silica (sand), magnesium, aluminum (clay), lime, and some metallic oxides. The proportion in which these substances vary, or, occasionally, the presence of some other substances, determines the quality and use of the sand.

There is little to aid the beginner in selecting a molding sand or in applying it to its proper use. This either must be left to some one experienced in the use of sand or must be determined by chemical analysis.

To be refractory, a sand must contain a large amount of silica ; if, however, it has more than a certain per cent, the sand cracks in drying, is not impervious to the liquid metal, and is not compactable, because of the lack of cohesion. The alumina and magnesia are important factors in molding sand, as they render it plastic and cohesive. Since magnesia binds the sand very thoroughly together, the amount contained in the sand should be small, else the porosity will be lost. Alumina has a tendency to vitrify at the temperature of molten iron, therefore the amount must be small. Iron acts in the same way as alumina and is beneficial as long as the total amount of iron and alumina is small. Both metallic oxides and lime are harmful. The metallic oxides must not exceed 4 per cent nor the lime I per cent.

Thus it can be seen that a good sand should contain silica with a little alumina, and that a small amount of iron and magnesium does no harm when the whole is so proportioned as to fulfill the following requirements :

1st. A free passage of air, gas, and steam ;

2d. Withstanding the heat of the metal without fusing ;

3d. Easy separation from the cold casting, giving a smooth, clean surface ;

4th. Sufficient compactness to resist the pressure of the metal.

To be serviceable a sand must answer the foregoing requirements. It is obvious, however, that one grade of sand will not do for both very light and very heavy work, because the heat is so much greater with a large casting than with a small one. Also, a large casting need not be so smooth as a small one. With the small casting, a sand of fine grain is needed, containing a little more alumina than the coarser-grained sand required for heavy castings ; and since the heat is less, the sand need not be so refractory, and may therefore contain less silica and more alumina, as there is less need of venting. The reverse is true in the case of heavy castings.

Grades. — This difference in work, or in the size and weight of castings, then, gives rise to three general grades of molding sands: (i) light, (2) medium, and (3) heavy. The light sand is used on small work that has fine details, such as that found on stoves. The medium sand is used when the castings range in weight from a few pounds to one or two hundred. The heavy sand is suitable for large work, such as heavy machinery and engines. There is no hard and fast rule determining the chemical analysis and the size of the grain in these grades of sand ; still, the following will serve to indicate in general the amount of sihca and alumina each grade should contain.

1. Light Molding Sand : 1

Silica

Alumina.

Degree of fineness .

2. Medium :

Silica

Alumina.

Degree of fineness .

3. Heavy:

Silica

Alumina

Degree of fineness .

Sand for brass (very fine) Silica Alumina .

Iron Degree of fineness .

82 per cent 10 per cent 85

85 per cent 8 per cent 66

88 per cent 6 per cent 46

78 per cent 8 per cent 5 per cent

The degree of fineness is determined as follows : " An average sample of the sand is passed over five different mesh sieves, ranging from a 20 mesh up to 100 mesh to the inch.

1 See the complete analysis in the Appendix.

The percentage passing through each sieve is used in the determination for fineness. By adding together the amounts that passed through each different sieve and dividing this by 5, the number of sieves used, one gets the average per cent that passed through all the sieves, which number is used to designate the grade of sand," or the degree of fineness. For example, the amount of a certain sand passing through the different sieves is as follows : ^

Per Cent

ICO mesh 15.40

231.90 -^ 5 = 46.38 = degree of fineness. This is a coarse or heavy sand.

Free Sands

Free sands are sands having little or no clay mixed with them. There are two kinds : sharp, or river, and beach sand. The sharp or river sand has sharp, angular grains, and the beach has round grains. Both are used in core and daubing mixtures and for parting sand. The sharp sand is better for the core and daubing mixtures, because the angular grains interlock with one another, making a strong mixture.

Core Sands. — Free sand, rock sand, and the debris of abraded rock are employed in making cores. Since a core is almost entirely surrounded by the hot metal, it must be refractory and contain no alumina, as the alumina would cause the cores to cake and be hard to remove from the casting. It should also be free from gypsum and salt.

Parting sand is used on a mold at the joint, or place where the parts of the mold are to separate, to prevent them from sticking to each other. It should have a uniform, fine grain and should be free from any substance that draws or retains moisture. Rat-

"^ A Treatise on Molding Satid. Trade publication of H. S. Vrooman.

tier dust (burnt sand shaken from the castings in a rattler), brick dust, and pulverized blast-furnace slag make the best partings, though charcoal is sometimes used when a very close joint is desired for brass work.

Facing sand consists of the ordinary molding sand with a per cent of coal dust or other facing material added to it, and thoroughly mixed and tempered,^ so that the mixture has the proper cohesion to retain the form of the pattern against the washing action of the metal when the mold is being filled. For economy this sand is riddled next to the pattern and the balance of the flask filled with the old sand from the foundry floor.

Loam is a soil chiefly composed of siliceous sand, clay, and carbonate of lime, with some oxide of iron, magnesia, and various other salts, and also with decayed animal and vegetable matter. It is, next to molding sand, the most important material used in the foundry. Loam will part with its combined water at a red heat, and at the temperature of molten iron that containing carbonate of lime will fuse and become vitrified. Loam containing iron, alumina, and silica is refractory, and therefore desirable, while that containing pyrites, lime, and alkalies is objectionable. When more than 5 per cent of lime is present in the loam, it should be rejected. When flint pebbles are present, they should be picked out before the loam is ground in a mill.

Black loam is a cheap loam having strong binding properties which make it suitable for mortar for setting the brick work, in loam molding, for the first coating of round cores, which must be strong, and for sealing cracks.

I FACINGS

A facing is a material incorporated with the sand, which is riddled next to the pattern or is dusted over the sand after the pattern has been removed.

1 Method of mixing and tempering described in Chapter III.

The purposes of a facing are :

I St. To prevent the sand in the mold from being burned ; 2d. To make castings peel, — that is, to leave the sand clean ; 3d. To make the castings smooth and bright ; 4th. To reduce the expense of cleaning the castings.

These results are accomplished in two ways :

1st. By filling the pores between the grains, a smooth surface

is given to the sand ; 2d. By burning slowly, owing to the heat of the metal, a thin film of gas is maintained between the iron and the sand. This film prevents the burning out of the alumina and the consequent roughness of the casting.

To accomplish these results the following precautions should be observed :

1st. The facings must be finely ground; 2d. They must not burn easily;

3d. They must adhere firmly to the face of the mold, to prevent them from being washed away by the iron.

The materials used for facings are the different forms of carbon ; such as sea coal or gas coal, graphite, charcoal, and coke. They are used because they will glow and give off gases but will not melt. The form in which the raw facing materials are obtained makes it necessary that they be ground by passing them through a series of crushers, or grinders ; the finest are then bolted.

Sea coal facing is made by grinding screenings of an ordinarily good grade of soft or gas coal, — one that is free from slate and low in sulphur.

Graphite is a soft, greasy, mineral form of carbon taken from the earth in large lumps that are much blacker than coal. Large amounts are mined in Rhode Island and other parts of North America, but the best and purest is imported from Ceylon.

Charcoal is a vegetable form of carbon made by charring or driving off the volatile constituents of wood by means of fire, in kilns or in heaps covered with dirt and sod. Either hard or soft wood charcoal is used for facings.

Coke is the carbonaceous matter left after driving off the gases from soft coal by heat, in a retort or oven. The coal must be very free from earthy materials, so that the amount of impurities introduced into the sand with the facing shall be as small as possible.

Talc is a magnesium silicate ore. It makes a good facing for some classes of work when very finely ground and shaken into the mold from a bag. It also makes a good core wash.

Blacking is a mixture of a facing, usually charcoal or graphite, and a clay wash or molasses water.^

MISCELLANEOUS MATERIALS

Fire clay is almost pure oxide of alumina. It comes from the same sources as sand, but is found in a lower stratum, having been washed away from the sand by water. It can be mixed with water and molded into almost any desired shape, and when exposed to the fire, it hardens into a very refractory, brickhke substance. It therefore serves very well as a fining where heat is to be resisted, and in daubing mixtures and clay washes.

Clay wash is fire clay mixed with water to such a consistency that it will leave a film of clay on an object when dipped into it. It is used as a base for blackings, wetting crossbars of flasks, gaggers, and in any place where a strong bond is required.

Core binders are materials used to stick or bind the grains of sand together in making cores, such as flour, rosin, linseed oil, etc. These materials are taken up in detail in Chapter VII.

Manufactured Preparations. — All foundry supply houses have specially manufactured or prepared parting sands, core binders, facing mixtures, daubing mixtures, and the like.

1 See Chapter VII.

Chapter II

Fig. I.

In performing the exercises taken up in this work only hand tools are used, and only such will here be described. They will as nearly as possible be taken up in the order in which they are required for use in the molder's hands.

Small work is usually done on a bench or bracket projecting from the wall. Large work requires that it be done on the floor. (The author is rather partial to floor work and requires the greater portion of the work to be done on the floor, whether it is large or small.)

Flasks. — Flasks consist of two or more frames of exactly the same length and breadth, though the heights may vary. The

frames are used to hold the sand while the impression of the pattern is being made.

The frames are made of either wood (Fig. i), iron (Fig. 2), or pressed steel (Fig. 3). Iron and steel flasks are much stronger and are used where a special class of work is done. Wooden flasks are used in jobbing shops, as they are much cheaper. They deteriorate very rapidly, however, and so need much care in handling.

Fig.

lO

They should be thoroughly inspected before use. The pressed steel flask (Fig. 3) is the most serviceable for school use, being lierht and strong and of reasonable cost.

The parts are held together in the same relative position by guide pins and sockets. The pins are in the top part, called cope; the sockets are in the bottom and middle parts. The bottom part is called the nowel, or drag, and the middle part, the cheek. When a flask has but a cope and a drag, it is called a two-part flask; when it has three parts, a three-part flask; and so on.

Fig. 4.

A flask may be ordinary, as shown in Fig i, or a snap flask; i.e. one having hinges on one corner and latches on the opposite corner, as shown in Fig. 4. Snap flasks are used for small

II work when the pressure of metal on the sides of the mold is not great. They range in size from 9" x 12" to i8"x2o". The advantage of a snap flask lies in the fact that when a mold is made up, the flask can be removed and used again immediately. The ordinary flask cannot be removed until after the metal is poured.

Fig. 5.

Large flasks usually have crossbars in the copes to help hold the sand while the copes are being removed. A flask with crossbars is shown in Fig. 5. The number and size of flasks that a school should have depend entirely on the quantity and size of the work done. Good results can be obtained if there is one 10" X 12" X 3" two-part steel flask for each student, and aside from these for general use three or four two-part snap flasks of each of the smaller sizes, and three three-part snap flasks of a suitable size for the grooved pulley, Ex. 11. Ordinary flasks, like Fig. i, can be made in any school wood shop as a regular exercise.

Slip Case. — A slip case (Fig. 6) is a frame which is slipped around the sand, after the snap flask has been re-

FiG. 6.

Fig. 7.

moved, to protect the mold until the metal has been poured. There should be about three cases for each snap flask.

Moldboard or follow board (Fig. 7) is a board the size of

the outside dimensions of the flask, and strengthened by stiff cleats. The drag and pattern are placed upon this board in making up a mold.

Bottom Board. — This is a board similar to the moldboard. The mold rests upon this board until poured. A school should be supplied with one moldboard and two or three bottom boards for each flask.

Riddle (Fig. 8) is used to sift the sand that comes next to the pattern. It should be 16 to 18 inches in diameter with oak rims and galvanized iron wire cloth, No. 8-12.

Shovel. — In the foundry the flat-bladed shovel (Fig. 9) is used for cutting, turning, and in general for handling the sand. The flat blade is best since it is often desirable to let the

sand slide off from the side of the shovel when working on a bench.

Rammers (Fig. 10) are used for tamping or ramming the sand in the flasks. There are two kinds, — bench rammers and floor rammers.

The bench rammer is short and made of wood, while the floor rammer has cast iron ends on a wooden bar about three and a half feet long. In foundries where a great deal of large work is done, and where compressed air is to be had, pneumatic rammers are sometimes used. One end of the rammer is called the

Fig. 8.

peen and is shaped like a dull wedge. It is used for packing

the sand around the edges of the flask and in the corners of some

patterns. The other end, called the butt, is

a short cylinder with a flat face and is used

for compacting the sand in the body of the

flask.

Straightedge (Fig. 11) is a piece of metal or wood having a thin edge for leveling the sand with the top of the flask. Each student should be provided by the school with one riddle, shovel, rammer, and straightedge.

Trowels (Fig. 12) are used for cutting the sand down to the parting lines, and for shaping the large faces of the mold.

Three shapes are generally used : (a) The square trowel for getting into square corners; (d) the round-pointed finishing trowel; (c) the sharp-pointed finishing trowel, used for both coping out and finishing. The round-pointed trowels are the most useful. The size of the trowel is determined by the length and width of the blade.

Slicks. — Slicks are used, as their name indicates, for slicking over the parts of a mold and for patching small breaks. There are a great many varieties on the market, used for various classes of work. The shapes shown (Fig. 13) are the ones most commonly used. Slicks are designated by the shapes of their

Fig.

D ^ blades, and sizes by the widest part of the widest blade ; they I'l'- II • run from i to i| inches.

The shapes are {a) taper and square, (d) heart and oval spoon, (c) heart and leaf, (d) heart and square.

Lifters. — A lifter (Fig. 14) has a long, narrow blade on one end and a short foot at right angles to the blade on the other. They are used for cleaning and finishing the deep and narrow portions of the mold. ^ ^ ^^ ^

There are two styles: (a) bench lifters and {l>) floor lifters. The sizes vary from ^" x 10 " to i" x 20" for floor lifters, and ^^g to I inch for bench lifters. Each student should provide himself with a trowel and either a slick or a hfter. It is well for each one to get a little different style.

Bellows (Fig. 15) are used for blowing the dirt and sand from the work. There should be one for every two or three students.

A sprue plug (Fig. 16) is a cylindrical piece of wood, tapered. It is used for making the sprue or runner through which the metal is poured. The sizes vary with the work and the depth of the cope. The school should be supplied with a large assortment, varying from | to i l inches in diameter and of

various lengths.

Corner slicks (Fig. 17) are used for dressing or squaring the corners. There are outside and inside corner slicks, ranging in size from i to 3 inches.

Corner slicks are not much used on small work, but it is well for a school to have one of each style.

Se/7cA

Swabs and sponges are used to moisten and pack the sand around the edges of the pattern before drawing. Swabs (Fig. 18) are usually made by wrapping one end of a bunch of hemp fiber, 6 or