Search Documents

By J. F. Tavernelli, L. F. Coffin

The deformation and fracture characteristics of eight metals subjected to fully reversed cyclic strain ranging from 0.2 to 50 pct were investigated at room temperature. Strain-hardening characteristics unique to the interna1 structure of a particular metal were found. Complete removal of the strain-hardening effects resulting from prior deformation was brought about by subsequent cyclic strain. Further support for the validity of the inverse relationship between the plastic strain range and the square root of the number of cycles for failure is given. THE resistance of materials to cyclic plastic strain is of interest both from a fundamental and practical point of view. It is now a well-accepted fact that fatigue failure in metals is a consequence of the localized slip deformation which occurs within the individual crystals of metal.'-' Hence the failure process should be strongly dependent upon the magnitude of the gross cyclic plastic deformation of the metal under conditions where this is a measurable quantity. Therefore, an experimental investigation of metals in which the cyclic plastic strain is the independent variable should shed new light on some of the basic aspects of the problem. From the practical point of view, there are many uses for information relating to the cyclic strain resistance of metals. One is the case of thermal stress fatigue where fatigue failure can occur as a consequence of a com- paratively few cycles of thermally induced mechanical deformation. Another is the mechanical working of metals where large cyclic strains are employed. In recent years several publications have appeared relating to the cyclic-strain resistance of metals,8-11 dealing mostly with the fracture aspects where the temperature is cycled simultaneously with the mechanical strain. Some work has been reported on the cyclic-strain resistance of metals at constant temperature, again oriented more toward the fracture aspects of the problem than the deformation aspects. 12-16 The present research investigation was undertaken to obtain information regarding the deformation characteristics of several metals whose structure-property relationships were simple and straightforward under conditions of both cyclic and monotonic strain. It has been shown for example that under cyclic-strain conditions some materials will strain harden, while other materials, particularly cold-worked structures, strain soften and these effects required further clarification.8,17-19 It was also de-

Jan 1, 1960

By Robert P. Koenig

FOR the first time other than on occasion of war the people of the United States are experiencing full-scale participation in world affairs. Public concern has seldom been so involved with conditions and events beyond our own continental limits. Our interest is not wholly of recent origin. Over the years the activity of the United States as a world power and an important trading nation brought about the widening of our political interests and the progressive interrelation of our economy with that of the rest of the world. Some may see in our present phase of world-wide activity the natural consequence of our continued growth. Such observers must also be aware that within recent years our importance in world affairs has been considerably increased. For within the space of an extremely short period events have occurred that have literally jet-propelled the United States into the role of a leading participant in the conduct of world affairs. Little of the choice of this role was left to us. The decline of power in western Europe, the ascendancy between the Elbe and the Pacific shore of an obviously antagonistic force, our earnest endeavor to secure international control of atomic energy, the necessity of providing relief and rehabilitation to war-ravaged areas, and the police work that must be done in occupied territories are problems which have risen in great measure without our help-but they cannot be solved without it.

Jan 1, 1948

By C. L. Clark

EVERY user of steel should ask himself whether or not he is taking full advantage of the discoveries of the steel metallurgists during the last few years, or is merely buying grades that looked to be the best five or ten years ago for various specific purposes and have since proved perfectly satisfactory in his plant. If he has not kept abreast of the times, then it is probable that something better has been developed, or something just as good that costs less. Though this article will have to do with steel for high-temperature applications primarily, marked advances have been made in steels for other purposes as well.

Jan 1, 1940

By M. A. Hunter

CHAIRMAN M. A. HUNTER. UP to this time our stress-corrosion sessions have been concerned with stress-corrosion cracking in brass. In the succeeding sessions a variety of other products which are susceptible to stress-corrosion cracking are to be considered and this afternoon's session is to be devoted to stress-corrosion cracking in light metals. The problems you have had to deal with up to now in brass have been very simple ones. From this time on the complexities become greater. You have already learned in the preceding sessions, that copper is not susceptible to stress-corrosion cracking and when you begin to alloy it with 3 per cent or larger proportions of zinc, then stress- corrosion cracking ensues. You apparently have few complications in the copper alloys you make. There is apparently no precipitation on the grain boundaries in the brass, and no precipitation within the metal itself. So, on the whole, the problem is a simple one. Yet it has been with the brass people for a very long time and it is apparently not yet settled from the fact

Jan 1, 1945

By Louis Raymond, John E. Dorn

The object of this investigation was to analyze the recovery that arises when the stress on a specimen undertaking creep is reduced. For this purpose annealed specimens of high-purity aluminum were precrept under a stress of 1000 bsi to a strain of 0.08 following which the stress was reduced for various periods of time to 10, 250, 500, or 700 psi. When the original stress was reapplied the subsequent creep curve lay above that for the unre-covered state and below that for the original annealed state. Analyses on the kinetics of this recovery as a function of the temperature gave a stress-sensitive activation energy that decreased as the reduced stress was increased from a value of 64,000 cal per mole at 10 psi to 37,000 cal per mole at 750 psi. Recovery was also detected and measured during creep under the reduced stress. Following a short initial period, the creep rate under the reduced stress increased monotonically until it reached the secondary-creep rate for the reduced stress. The temperature dependence of this phenomenon was also shown to be correlatable in terms of the previously deduced activation energy for recovery. The activation energies for creep of most pure metals at high temperatures have been shown to agree well with those for self-diffusion.'j2 Since the true secondary stage of creep is usually due to the steady-state balance between the rate of strain hardening and the rate of recovery, it is generally thought that the activation energy for recovery of the creep-induced substructure equals that for creep itself. A shoft time ago, however, Ludemann, Shepard, and Dorn~ found that the activation energy for recovery of the creep-induced substructure in high-purity aluminum under zero stress was almost twice that for self-diffusion, namely about 65,000 cal per mole; obviously recovery under reduced stresses differs in some significant way from the recovery that accompanies the secondary stage of creep. The major purpose of this investigation is to study the effect of stress on the re- covery of the creep-induced substructure in order to provide a better understanding of the recovery mechanism itself. EXPERIMENTAL TECHNIQUE High purity aluminum, containing 0.004 pct Cu, 0.002 pct Fe, and 0.001 pct Si, used in this investigation, was in the form of 0.100-in.-thick sheet which has been cold-rolled to the H-18 temper. Creep specimens were milled from the sheet with their tensile axes in the rolling direction. All specimens were then heated at 686°K for 1 hr followed by air cooling in order to produce an annealed structure which exhibited a uniform equiaxed grain size of about 4 grains per mm. Tests were run in creep machines fitted with Andrade-Chalmers type of lever arms so contoured as to maintain the stress constant to within 0.05 pct of the reported values. Constant temperatures to *O.l°K were obtained by complete immersion of each specimen in a temperature-controlled and agitated bath of molten KN02-KNOs mixture. Where changes in temperature were involved, the change was effected in less than 2 min by manually replacing one bath by another controlled at the second temperature. Displacements over the gage section were sensed by linear differential transformers, the output of which was autographically recorded. The calculated strain measurements were sensitive to 5x EXPERIMENTAL PROCEDURE The following analyses are based on extensions of the previously announced effect of the temperature on the creep strain,2 namely for a = constant, where e = the total true tensile creep strain for a given applied true tensile stress, t = the duration of the test, R = the gas constant, T = the absolute temperature, Q, = the activation energy per mole for creep which is independent of the stress, / = a function of 8, = and of the stress, and a = the stress. The validity of this correlation for high-purity aluminum is demonstrated in Fig. 1 for temperatures in the near vicinity of 600°K; the activation energy for creep, Q,, which is approximately that for self-diffusion, is insensitive to the applied stress

Jan 1, 1964

By ROBERT. RICHARDS

I. INTRODUCTION The object of this paper is to enlarge the field of settling velocities treated by me in my former papers, Close Sizing Before Jigging, and Sorting Before Sizing.' There seemed need of work both on coarser and on finer sizes. Messrs. A. Sidney Warren and M. L. Nagel undertook the investigation for the coarser sizes, from 12.85 mm. down to 2.05 mm. diameter. Their work, because of the closer spacing and because of the increased number of observations and consequent stronger averages, called for a revision of the former work. Messrs. G., A. Barnaby and Ralph Hayden undertook this part of the work, from 2.49 mm. down to 0.28 mm., which is near the limit of sifting. Their work covers the ground much more minutely and comprehensively than the former papers. There remained to be covered the portion of the field too fine for investigation with the sieves. This part, covering the range of grains from 0.48 to 0.03 mm., was undertaken by Mr. E. S. Bardwell. For it he used the elutriation method. II. THE FIRST, OR COARSEST, SECTION OF THE FIELD. The first desideratum in this investigation was a series of sieves for sizing the sands preparatory to making the tests. It became necessary, therefore, to decide on a sieve-scale for this purpose. A sieve-scale is a series of sieves in which the dimensions of the holes of the successive members form a series increasing by a. definite ratio. There are three natural sieve-scales : 1, progressing by doubling the width of the hole for each suc-

May 1, 1907

By A. O. Bartell

Do you know that valuable clues to the geology and mineralization of a district can be found in a handful of sand from a stream bed draining the area? This handful of sand has a story to tell to those who have a little patience. The handful of sand may contain tiny specks of valuable minerals (gold, scheelite, cinnabar, chromite, tourmaline-to mention a few), that will lure you upstream with the hope of uncovering a new deposit. More practically, this handful of sand can indicate the type of rocks that are exposed by the drainage system. Any mineral that has a specific gravity of 3.5 or higher can be separated from soil by panning. Garnet and pyrite, for example, can indicate an outcrop of metamorphic rock. In one district where the writer prospected, small boat-shaped orthorhombic crystals of topaz always indicated the presence of andesite outcrops.

Jan 1, 1948

By John T. Wizzard, R. P. Killmeyer, B. S. Gottfried

The Coal Preparation Branch of the Pittsburgh Energy Technology Center has developed a computer program to calculate the performance characteristics of coal washing devices. This program uses specific gravity analyses of the clean coal and refuse streams as input, and generates dependent and independent performance criteria for the washer. Partition curves are internally represented in a functional form by a Weibull function. Performance criteria generated by this computer program are compared to manually calculated performance criteria for air tables, Dynawhirlpools, Baum jigs, hydrocyclones, and dense medium cyclones. The comparisons show that the computer program gives results in close agreement with the hand- calculated values while greatly reducing the amount of time involved in performing the analyses.

Jan 1, 1983

By J. Fred Johnson

MORE ORE is mined in the Bingham District than in any other mining district in Utah. In addition to the open-pit operations of the Utah Copper Co., there have been, many large underground mines. Until recent years the principal production was from the Jordan and Commercial limestones, but in the last eight years valuable ore deposits have been developed in the so-called alphabetical or "A," "B," "C," and "D" limestones, mainly by the U. S. Smelting, Refining & Mining Co. The value of these developments has led the company just mentioned to acquire large holdings in the district and within the last year to install at the Niagara shaft a hoist capable of going to a vertical depth of 4000 ft., or 1800 ft. deeper than the present lowest level. Ore from Bingham has been the chief factor in enabling the

Jan 1, 1934

By T. A. Rickard

"The chief aim in style ought to be absolute precision", said Flaubert. "There is only one noun that can express your idea, only one verb that can set that idea in motion, and only one adjective that is the proper epithet for that noun." Let this be your motto. The engineer tries to be exact in all his measurements; he should measure his language with similar exactness. The technical term is a word of precision. It is not only precise, it is a word-saver. To the unscientific the earth is "a ball slightly flattened at the poles, something like an orange". To the scientific it is "an oblate spheroid". A similar contrast between the precision of the technical term and the vagueness of common words is afforded by a conversation between Ivanhoe and Rebecca: "' What device does he bear on his shield?' asked Ivanhoe. 'Something resembling a bar of iron, and a padlock painted blue on a black shield.' 'A fetterlock and shacklebolt azure', said Ivanhoe "-using the technical terms of heraldry. It is good style in writing, however, to adapt your manner of expression to the intelligence and experience of the person or persons to whom the writing is addressed. The description of a mine should be worded differently according as it is intended to inform a mining engineer, a director, or a bishop. REMEMBER THE READER. It is as incorrect to write in a technical way for a non-technical reader as to write in a popular way for a technical or scientific reader. That style is best which enables the writer to place himself in the closest mental touch with his reader, to establish the maximum of sympathetic understanding. Let your precision be\ proportioned to your accuracy. You should not try to be precise in matters that do not admit of

Jan 1, 1931

By A. STEPHENSON

EXPERIMENTAL work conducted at the Petroleum Engineering Laboratory of the University of California by L. C. Uren, J. Domercq, Jr., and J. Mejia has shown that small diameter wells offer tremendous resistance to the flow of fluids in their immediate vicinity. This resistance is due in part to the constriction of the area through which the fluids must pass as they approach the wall of the well, but is also accentuated by the increased volume which results from gas expansion. The latter in turn is a function of the deduction in pressure, the fundamental cause of fluid movement. If the diameter of the bore is enlarged several diameters, the capacity of the well, or the volume of fluid passing per unit drop in pressure per unit of time, is greatly increased without necessitating such high fluid velocities. The fundamental features which should be taken into consideration in the design of casing joints were stressed by J. B. Graham and E. E. Smith. These involved such points as correct thread design, high efficiency, and small diameter, together with the insurance that leakage will absolutely be prevented. The practical features of such design were ably discussed by engineers from leading steel manufacturers.

Jan 1, 1935

THE man who forgot to mail the letters his wife gave him was for once justified at Tulsa, for envelopes, scratch paper and tablecloths were all in demand and through the two days of the meeting of the Petroleum Division, pencils were busy everywhere sketching out diagrams, drawing curves, figuring, or just taking notes. Those attending took the serious papers seriously, and discussion was wide-ranging but pointed. Despite the highly technical character of the papers presented, the chairmen had never to call for discussion; it was only necessary to say the paper was open for it. Both days the meetings lasted until after five in the afternoon, and it was enthusiastically voted to advance the meeting hour on Friday, in order to give more time. In all, ten papers, abstracts of which appeared in MINING AND METALLURGY for October, and copies of all but two of which were available in print, were presented in the two days, and no more could have been handled to advantage in that time. All but one of these dealt with problems of production engineering. That, the opening paper, was a general review of demand, supply and price in 1928, by Campbell Osborn, in which he argued for the price control of production and showed how the economic conditions determined development. J. Elmer Thomas presented a carefully prepared review of the same data, but came to somewhat different conclusions as to trend, and J. E. Pogue pointed out that in recent years it has been the manufacturing rather than the producing industries that have been notably profitable. These and other discussions were too long to be reported here, but will be printed in full later.

Jan 1, 1928

By Woolsey Johnson

THE object of this paper is to, describe the several necessary characteristics of the zinc-retorting charge and to show how by certain improved methods; the large excess of coal, over that theoretically required, can be reduced, thereby effecting an increase in the smelting capacity of a retort plant as well as other economies. In the Southwestern zinc works a charge of roasted zinc ore with a side mixture of carbonates and silicates, analyzing on the average 50 per cent. Zn, is mixed with 55 or more per cent. of its weight of a mixture of coal and coke analyzing 60 to 70 per cent. fixed carbon. . The ore is of varying fineness and the coal and coke are usually crushed in a semi-moist condition through a 3/8 -in. screen. With ores of a slaggy nature, this coal proportion is increased, sometimes to as much as 100 per cent. of, the weight of the ore. With carbonate ores, or where anthracite screenings with higher carbon content are cheap enough, the percentage of reducing agent is cut to 45 per cent. or even somewhat lower. The average charge per retort for a monthly run of a plant on ore, as distinguished from retorts on blue-powder, ladle-skimmings and other between-products, runs from 60 to 66 lb., with a mean of 63 lb. for the Southwest with standard retorts of 8 ½ -in. inside diameter and 50 in. long inside, using roasted sulphide ores. Conditions will change these figures, but 40 lb. of ore per cubic foot of retort space is, I believe, an average in the better-operated plants. Since the rise in. the price of spelter, the tendency has been to overcharge. To remove the slag that is formed when retorts are overcharged, extra men are put on to "gum-chisel" the retorts to prevent "set" furnaces and "butchered, retorts." Taking the above conditions as premises, we find that from four to six times the amount of coal necessary for the reduction is used, as is evidenced by the fact that the residues analyze as high as 35 per cent, fixed carbon. There are good reasons why this excess of fixed carbon must be used and perhaps these can be best explained by a description of the metallurgical requisites of a zinc charge. We may enumerate these as follows: 1. High reducing power, especially at the end f the shift, to reduce any carbon dioxide to monoxide and bring about a good condensation

Jan 2, 1918

By A. L. Holley

THE occurrence of this gas, in quite appreciable. quantities, has been observed for many years in its escape along the creeks of Western Pennsylvania, and more recently, in much larger quantities, from the oil wells in and near Venango County. Within about five years several gas wells have been struck, from which the gas has escaped continuously in prodigious quantities and at great pressure. During the last year a systematic attempt has been made to utilize the flow of gas from one of these wells, and results have been reached which were quite unexpected. This well, near Leechburg, Armstrong County, is about twenty miles northeast of Pittsburgh, on one of the side tributaries of the Alleghany River. It had been drilled in search of oil to a depth of 1250 feet in 1871, but none was found. A great flow of gas was developed, however, accompanied by a slight spray of salt water, and this has continued with little or no diminution to the present time. The gas in its escape has been discharged through a 5-inch pipe, and at a pressure of from 60 to 80 lbs. per square inch, but no exact determinations, either of the pressure or quantity, have been made. The rolling mill of Messrs. Rogers & Burchfield is on the opposite side of the river, and it has been for some years devoted to the production of fine grades of sheet iron from charcoal pig metal, by puddling and in knobbling fires. The usual weekly product of the mill has been 30 tons of No. 30 tin plates, and 50 tons of No. 24 to 28 sheets. The well was bought by this firm for $1000, and the gas is led across the river, a distance of about 500 feet, through a 3-inch pipe. It is distributed through half-inch pipes, and at a pressure of about 45 lbs. per square inch, to several of the furnaces, but a large fraction of the total flow of gas is still wasted at the well. No essential alteration in any of the furnaces has been found necessary in the use of the gas fuel, except to brick up the fire-bridge and to put in the gas and air pipes. The old grate used for coal is loosely covered with bricks and cinder, so that a slight percolation of air may take place through them. The gas is admitted through a half-inch pipe, and blows toward the fire-bridge through 18 or 20 one-eighth inch jets. The air is blown in at about 2 lbs. a

Jan 1, 1876

By W. McA. Johnson

The object of this paper is to describe the several necessary characteristics of the zinc-retorting charge and to show how by certain improved methods, the large excess of coal, over that theoretically required, can be reduced, thereby effecting an increase in the smelting capacity of a retort plant as well as other economies. In the southwestern zinc works a charge of roasted zinc ore with a side mixture of carbonates and silicates, analyzing on the average 50 per cent. Zn, is mixed with 55 or more per cent. of its weight of a mixture of coal and coke analyzing 60 to 70 per cent. fixed carbon. The ore is of varying fineness and the coal and coke are usually crushed in a semi-moist condition through a 3/8-in. screen. With ores of a slaggy nature, this coal proportion is increased, sometimes to as much as 100 per cent. of the weight of the ore. With carbonate ores, or where anthracite screenings with higher carbon content are cheap enough, the percentage of reducing agent is cut to 45 per cent. or even somewhat lower. The average charge per retort for a monthly run of a plant on ore, as distinguished from retorts on blue-powder, ladle-skimmings and other between-products, runs from 60 to 66 lb., with a mean of 63 lb. for the Southwest with standard retorts of 8 1/2-in. inside diameter and 50 in. long inside, using roasted sulphide ores. Conditions will change these figures, but 40 lb. of ore per cubic foot of retort space is, I believe,'an average in the better-operated plants. Since the rise in the price of spelter, the tendency has been to overcharge. To remove the slag that is formed when retorts are overcharged, extra men are put on to "gum-chisel" the retorts to prevent "set" furnaces and "butchered retorts." Taking the above conditions as premises, we find that from four to six times the amount of coal necessary for the reduction is used, as is evidenced by the fact that the residues analype as high as 35 per cent, fixed carbon. There are good reasons why this excess of fixed carbon must be used and perhaps these can be best explained by a description of the metallurgical requisites of a zinc charge. We may enumerate these as follows: 1. High reducing power, especially at the end of the shift, to reduce any carbon dioxide to monoxide and bring about a good condensation

Jan 1, 1918

By G. S. Rice

IT is evident from Professor Louis' remarks that he holds a different opinion on certain phenomena connected with a specific type of surface subsidence from mining than is held by many engineers in the United States. The question which appears to be at issue is whether or not the line or plane of "draw" produced in ground movement resulting from extraction of pillars may, under certain conditions, be vertical or even inclined toward the workings rather than inclined for- ward over the unworked mineral, as it is universally agreed occurs in mining by the longwall advancing method. In discussing this case it is well to take the simplest condition, such as specified by Professor Louis, of a flat bed, whether it be coal, iron or other mineral, where the overburden is stratified rock and where there is no overlying quicksand. Professor Louis says in effect that his experience is that the ultimate angle of draw is always positive and inclined 5" to 15" from the perpendicular over the unwrought mineral. My experience under Illinois coal-mining conditions is that .'where longwall advancing is used the draw is always positive as Professor Louis describes it, but that in extracting of panels by withdrawal of pillars, the ground movement is manifested, after the first roof' beam break, by the forming of an unstable dome over the goave. Then subsequently, by the falling of individual slabs from the under side, the dome gets larger and higher until it breaks through to the surface of the rock., Up to this time, arch stresses buttress the rocks above the solid coal or mineral. When, however, after. the dome breaks through and the central hole - #enlarges so the arch is no longer sufficiently supported -the stratified rocks cantilever out .from over the solid unworked mineral and tend to break off in masses triangular in vertical cross-section, until the broken loose material, sliding down against the solid rock, .has such a thrust that it balances the tendency ,for the solid stratified rock to break away and slide toward the excavation.

Jan 1, 1929

CONTENTS [The Nature of Strain Markings in Alpha Brass (paper by J. E. BURKE and C. S. BARRETT, Met. Tech. Feb. 1948. TP 2327). ......................... 2 X Ray Studies of Twinning and Untwinning in Magnesium Alloys (paper by J. B. HESS and R. L. DIETRICH, Met. Tech. Feb. 1948. TP 2328) ................ 11 ]

Jan 1, 1948

By W. L. Austin

The only essential difference among the three methods of collecting the precious metals from their low-grade ores by fusion is comprised in the nature of the vehicle in which those metals are concentrated. If lead- or coppper-ores are used, the processes are respectively lead- or copper-smelting; but when the sulphide of iron forms the matrix in which the gold and silver are collected, the process is known as pyritic smelting. The latter method presents rarely any advantages when lead- or copper-ores are available at rates which permit profitable treatment. Pyritic silver-smelting, defined by Percy as " the smelting of silver-ores, which are either free from lead or do not contain it in sufficient quantity to collect the silver, in conjunction with pyrites, in order to produce a regulus in which the silver may be concentrated," is not, as the name would imply, confined to ores of this metal alone, but embraces auriferous silver-ores, or even gold-ores simple. This method of collecting the precious metals from lowgrade dry ores, employed at Freiberg by Barthel Kohler in 1585, does not appear, up to the present, to have been introduced into this country on a working scale. And yet the possibility of getting rid in a single operation of all the earthy or siliceous gangue of a lowgrade ore and concentrating the precious metals in a matte without loss of lead (which includes gold and silver) by slagging, or volatilization, at the same time producing a highly siliceous slag, very nearly if not quite as clean as is usual in lead-smelting, certainly commends itself. In some parts of the country, owing to the com-

Jan 1, 1888

By G. B. Kasik, George Sachs, George Espey

IT has been reported frequently that the hardness and strength vary over the cross section of cold-worked, particularly cold-drawn, material. Brass rod and wire usually has been found to possess a maximum strength and hardness near the surface.1,2 According to Sachs,1 the center fiber has about the same strength as a wire stretched by the same amount in a tensile-test machine, the strength increasing toward the surface (Fig. I). These differences are particularly large for wire given a small reduction on drawing through a die with a wide opening. However, with increasing reduction and hardness, a tendency to form a thin soft surface skin becomes apparent. On the contrary, copper wire has usually been found to possess a soft surface skin" and it has been reported by Harris3 that during the cold-drawing of hot-rolled wire the surface layer becomes increasingly softer than the core, while the layer of maximum strength moves toward the core, it being found near the surface at first. The increase of strength and hardness from the core to the skin is readily explained by the observation that, in addition to the stretching, the layers of a rod or wire are sheared more the closer they are to the surface.1,6-8 However, the presence of a soft surface layer can be attributed only to an annealing effect. The source of such a softening might be the extremely high temperature that originates from the friction between [ ]

Jan 1, 1941

By E. G. SINCLAIR

DRILLING wildcat wells in Wyoming differs a little from methods used in any other field. Here it is always advisable to start the hole as large as is convenient in order to carry each string of pipe as far as possible, so that drilling can be continued a thousand feet deeper if necessary, as there is always sand a few hundred feet ahead that really ought to be tested. This plan may seem ambitious, but if it is adhered to, it will save a great deal of trouble before the well is completed. In making the location, one representative from the operating department and one from the geological department should work together, so that the well may be in the best possible place for obtaining oil and the most feasible place to drill for the operating department. In Wyoming nearly all wells are drilled with standard tools, as with them a better log can be kept and better time made in completing the hole. The shales of Wyoming are very hard and do not mix well in a wet hole. The shale cuts into large pieces, too large to be circulated out of the hole, and forms a mat on the rotary which soon cuts off circulation. Then if this mat cannot be jarred from the bit, the drilling string has to be pulled and the mat cut off from the bit with a pick or an axe. I have seen standard tools come out of a wet hole with 10 to 16 in. of mat on the bottom of the bit. Rotary tools have drilled wells satisfactorily in the Big Muddy field and at Billy Creek, but in the other fields the wells have been drilled much more economically with cable tools.

Jan 1, 1926