~3<ZO 
 
UBRAM OF CONGRESS 
 
 003 129 835 
 
>rm No. 361 
 
 NOTES 
 
 ON 
 
 INSPECTION OF 
 
 STEEL FORGINGS 
 
 NAVY DEPARTMENT 
 
 BUREAU OF ENGINEERING 
 
 2 
 
 WASHINGTON 
 
 GOVERNMENT PRINTING OFFICE 
 
 1921 
 

 L\mm OF CONGRESS 
 
 JUNl 61.921 
 
 ^ teB *****W*Bitt*»M»rt( 1 *w«««>*jttji#t* M(l ^ w 
 
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 TABLE OF CONTENTS. 
 
 Par. 
 
 1. Contract and specifications 7 
 
 2. Manufacture of ingots 7 
 
 3. Inspection of ingots 7 
 
 4. Process of manufacture of forgings 8 
 
 5. Marking forgings for identification 8 
 
 6. Heat treatment 8 
 
 7. Test specimens 9 
 
 8. Testing. 9 
 
 9. Metallographic specimens 10 
 
 10. Inspection during machining 10 
 
 11. Inspection of finished crank shafts 11 
 
 12. Inspection of hollow-bored shafting 15 
 
 13. Final inspection 17 
 
 14. Small forgings 17 
 
 15. Stamping and weighing 18 
 
 (3) 
 
INTRODUCTION. 
 
 The following notes on the inspection of steel forgings are intended 
 for the information of the inspection force only. They have been com- 
 piled from reports of methods in use in the various inspection offices, 
 and I while they dofnot prescribe the procedure to be followed in the 
 inspection of this class of material, they may be found useful to assistant 
 inspectors not having had long experience. They should not be con- 
 strued as in any way modifying the requirements of the contract or 
 order, nor as limiting the scope of the inspection. 
 
 (5) s 
 
INSPECTION OF STEEL FORGINGS. 
 
 1. CONTRACT AND SPECIFICATIONS. 
 
 The assistant inspector should thoroughly familiarize himself with the 
 requirements of the contract or order and the Navy Department speci- 
 fications in accordance with which the material is to conform. Any 
 apparent inconsistency or condition in the contract or order which is 
 not entirely clear should be brought to the attention of the inspector in 
 charge of the district, and instructions obtained before the inspection is 
 begun. 
 
 2. MANUFACTURE OF INGOTS. 
 
 The specifications approve the use of acid or basic open-hearth fur- 
 naces and electric furnaces. When the furnace charge, consisting of 
 pig iron, steel scrap, and a suitable flux, has been reduced to the proper 
 carbon content, determined by means of ladle tests taken at varying 
 intervals, it is tapped and the molten steel drawn off in a ladle or ladles, 
 from which it is poured, usually from the bottom, into ingot molds. 
 The ingot molds are generally metal and so formed as to produce ingots 
 of cylindrical form with fluted sides, or of square cross section. (Sand 
 molds are not generally used when casting ingots for important forgings 
 on account of the slower cooling of the metal and consequent liability 
 to segregation.) The molds are tapered to insure ready withdrawal. 
 In some cases the metal is poured into the top of the molds, called "top 
 poured"; in others, through runners into the bottom of the molds, 
 whence it rises to the top, called "bottom poured"; and less frequently 
 into molds so arranged that the metal is subjected to hydraulic pressure 
 while in the partial liquid state, called "fluid compressed." After solidi- 
 fying, the ingots are removed from the molds. If practicable, heat may 
 be saved by transferring the hot ingot to the forge furnace, and after 
 soaking it may be forged. 
 
 3. INSPECTION OF INGOTS. 
 
 Provided ingots are not charged (hot) direct from the molds into the 
 forging furnace, they may be inspected for defects and the data obtained 
 recorded. The most common defects to occur in ingots are cooling 
 cracks and defects in the surfaces caused by the splashing of the molten 
 metal. The removal of these defects by chipping is permitted and the 
 extent to which chipping may be done is usually covered by the speci- 
 fications. In all cases the following data should be recorded: 
 
 (a) Name of the manufacturer. 
 
 (b) Heat number and serial number of ingot. 
 
 (c) Form of mold used; square, fluted sides, number of sides, etc. 
 
 (d) Dimensions and weight. 
 
 (e) Kind of furnace used (acid or basic; open-hearth or electric). 
 (/) How poured (top, bottom, or fluid compressed). 
 
 (<7) Approximate weight of ingot mold employed. 
 If the firm manufactures its own ingot'', the inspector should become 
 acquainted with the process employed. 
 
 (7) 
 
8 
 
 4. PROCESS OF MANUFACTURE OF FORGINGS. 
 
 Forgings are made both by hammer and hydraulic press, the larger 
 ones by the latter method, since in addition to the better facility for pro- 
 ducing the forging, a more thorough working of the metal is obtained. 
 The ingots, especially nickel steel, should be carefully warmed before 
 charging into a hot furnace. They are usually charged horizontally and 
 with the top of the ingot protruding from the furnace door, all space not 
 occupied by the ingot in the doorway being bricked up. Generally the 
 ingot is charged into the furnace so that not over 20 per cent will remain 
 cool. A chuck is attached to this cool top of the ingot by means of which 
 the ingot is carried to the press or hammer and turned while in the process 
 of being forged. In case of small forgings tongs are often employed. 
 The ingot is heated to the proper forging temperature, and soaked at that 
 temperature a sufficient time to become uniformly heated throughout its 
 mass. The ends of improperly heated ingots may when forged become 
 extremely concave or convex. Concave ends may result from forging 
 without sufficient soaking, thus the center being colder and consequently 
 harder than the surface. Convex ends may result from forging in cases 
 where the surface of the ingot, which has been properly heated, is allowed 
 to chill before forging is begun or to cool during forging. 
 
 In the forging of large shafts, etc., it may be necessary to reheat the 
 partly forged ingot several times before forging can be completed. 
 
 Navy Department specifications usually prescribe the per cent of top 
 and bottom discard. When forged to a predetermined size the required 
 amount of bottom discard is calculated, measured, and cut off. 
 
 The amount of top discard, including the tong hold, should be calculated 
 or weighed in order to determine that the required amount has been 
 removed. 
 
 Navy Department specifications also prescribe a minimum reduction 
 of cross-sectional area from the ingot to forging. 
 
 5. MARKING FORGINGS FOR IDENTIFICATION. 
 
 As soon as forged each forging should be stamped with a forging number, 
 usually supplied by the manufacturer, which should be a key to the 
 ingot number, and this record kept by the inspector. The inspector 
 should stamp the end of the forging "USN " and "M" (muzzle or top) or 
 "B" (breech or bottom) to indicate the relative position in the ingot. 
 These marks should be placed near the forging number. In case the 
 forging is rejected the serial number which it bears should not be again 
 employed for a replace or an additional forging. 
 
 6. HEAT TREATMENT. 
 
 The heat-treating equipments should be of an approved design and 
 such as to evenly heat and cool the forging. The pyrometers should be 
 so installed as to enable the inspector to satisfy himself that the forging is 
 being uniformly treated. Uniformity of temperature may also be noted 
 by the color, and if the forging is not of a uniform color before quenching, 
 it should be returned to the furnace and reheated. 
 
7. TEST SPECIMENS. 
 
 Upon the submission of the forging after heat treatment, test speci- 
 mens should be located in accordance with the specifications of the 
 contract or order. B and M test bars are taken from prolongations pro- 
 vided on each end of forgings. The diameter of these prolongations 
 should be as required by the specifications. In crank shafts, the section 
 withstanding the greatest stresses is represented by the W and X bars 
 and care should be exercised to guard against the drilling of holes or 
 otherwise treating the shaft in order to produce a special heat treatment 
 of the metal from which the test bars are to be taken. In all cases each 
 specimen should be stamped with the forging number, USN, and letters 
 indicating the location from where taken, that is, MI, MO, BI, etc. 
 Specimens for_ metallographic examination need not be located until 
 after the physical tests have been made. The removing of test speci- 
 mens may be accomplished by trephining, slotting, or otherwise machin- 
 ing. The burning out of a section of a forging from which it is proposed 
 to machine test specimens should not be permitted in cases when there 
 is any possibility of the temperature resulting from such burning, affecting 
 the test specimen. 
 
 8. TESTING. 
 
 The assistant inspector should indentify each test specimen after 
 machining, and check up the dimensions to determine that they have 
 been machined uniformly to the required diameter, and that the punch 
 marks are exactly 2 inches apart. The surfaces of all tension test speci- 
 mens should be free from tool marks and scratches. The excuse that 
 poorly prepared test specimens are to the advantage of the Government 
 should not be accepted, since accurate determination of the condition 
 of the steel in the forging is desired as well as the information as to 
 whether the steel is in full conformity with the requirements of the 
 specifications. In case the inspector does not actually operate the 
 testing machine, he should witness the operation and satisfy himself 
 that the machine is being operated in a proper manner and that correct 
 readings are obtained. 
 
 After breaking, each tension test piece should be examined for flaws 
 appearing along its walls, as well as the grain structure as indicated by 
 the fracture, and the assistant inspector should make note of the results 
 of this examination. 
 
 The measurements for elongation and reduction of area should b© 
 taken by the assistant inspector. 
 
 The bending test may be made under a hammer, press, or by means 
 of the testing machine. Specimens for bending tests should in all 
 cases be approximately of the cross sectional dimensions required by the 
 specification, except that specimens under the required thickness should 
 not be accepted. 
 
 Drillings for chemical analysis should be taken from that end of the 
 forging representing the top of the ingot and are usually obtained from 
 the bend test specimen, but may be taken from one of the ' 'M' ' tension 
 bars. 
 
 44498—21 2 
 
10 
 
 9. METALLOGHAPHIC SPECIMENS. 
 
 In cases where metallographic examination is required specimens for 
 this purpose should be taken in accordance with specifications of the 
 contract or order and should be properly marked and forwarded to the 
 Engineering Experiment Station at Annapolis, Md. These specimens 
 should be accompanied by Form N. Eng. 76, with all necessary in- 
 formation entered thereon. 
 
 10. INSPECTION DURING MACHINING. 
 
 (a) Inspection should be made during machining to detect defects. 
 Definitions for the most common defects in steel forgings are given al- 
 phabetically in the following subparagraphs: 
 
 (1) Check.— A variety of crack. (See crack.) 
 
 (2) Crack (also see seam). — A fissure which has opened due to strains 
 or to brittleness of the material. Those produced by rolling and forging 
 are known respectively as rolling cracks and forgina cracks. When 
 cracks are formed on the outside, due to the rapid heating of cold mate- 
 rial, they are called heating cracks or expansion cracks. Cooling cracks 
 or contraction cracks are due to the outside not being able to contract 
 uniformly during cooling; in castings this is termed checking. Thermal 
 cracks, hot cracks, or heat cracks are those produced by repeated alternate, 
 sudden heating and cooling of the surface. An internal crack or fissure 
 is one which has formed in the interior, but does not (usually) extend 
 through to the outside; this is due to excessive longitudinal strains, 
 either from cold working or from too rapid cooling from the outside. 
 
 (3) Ghost line, ghost.— A streak lower in carbon content than the 
 surrounding metal and visible to the unaided eye. Such streaks ap- 
 pear under the microscope as regions of excess ferrite and usually con- 
 tain nonmetallic inclusions of sulphides and silicates. During the 
 solidification of the steel certain elements tend to segregate in the por- 
 tions that solidify last. This results in the concentration of these ele- 
 ments not only about the top and center line of the ingot, but also on 
 the boundaries of the original crystals. Among the elements that thus 
 segregate are carbon, sulphur, silicon, phosphorus and oxygen. Some 
 of these elements, especially sulphur, occur in the form of complex non- 
 metallic inclusions, others, including carbon and phosphorus, immedi- 
 ately after solidification are in solution in the metal. When solidifica- 
 tion is complete therefore the boundaries of the original austenite crys- 
 tals are regions of higher than average carbon content. During cooling 
 from this point, however, the solubility of each of the various elements 
 is influenced by each of the other elements. Due to the influence of 
 -other elements the carbon migrates from the regions of the inter-crystal- 
 line segregation thus leaving regions of lower than average carbon con- 
 tent. When the metal is forged or rolled these low carbon regions are 
 elongated forming streaks of composition different from that of the 
 surrounding metal. These streaks are known as ghost lines. 
 
 (4) Lamination. — A layer of different composition than the metal 
 on each side of it. There may or may not be actual discontinuity between 
 this layer and the metal on each side of it. 
 
 (5) Lap. — A variety of seam. (See seam.) 
 
 (6) Pipe; piping. — A defect in ingots or castings. During the solidi- 
 fication of any casting, the action proceeds inward from the portion on 
 
11 
 
 contact with the wall of the mold. In this connection a core or interior 
 division of a mold is to be considered as a wall.) As solidification with 
 resulting contraction proceeds, since the metal itself is of smaller bulk 
 when solid than when molten, eventually a longitudinal cavity is left 
 near the top, where solidification last occurs, since below this point 
 any incipient cavity is immediately filled with molten metal. This 
 cavity is known as a pipe on account of its shape (also termed cavity, 
 contraction, cavity , void, vug, sink hole, shrink hole, draw hole). Liquid 
 contraction is that which occurs up to the point of solidification. Solid 
 ■contraction occurs after solidification is complete. 
 
 (7) Pit (scab, shell, spill). — A depression in the surface of material 
 caused by subcutaneous blowholes from which the skin has been burned 
 away, or from scale or dirt rolled or forged in, and which has subsequently 
 dropped out. Where the skin from a blowhole has not entirely burned 
 away but is not welded to the rest of the metal and may be removed 
 by hammering the piece it is called a scab, shell, or spill, and the material 
 is said to be scabby, shelly, or spilly. 
 
 (8) Seam. — A line of discontinuity in metal, visible on the surface 
 to the unaided eye. A variety of seam known as rook or roke, is a crack 
 which has been closed together but not welded; it is usually produced 
 by cutaneous or subcutaneous blowholes which have become oxidized. 
 A streak, of segregated nonmetallic inclusions, frequently occuring in 
 ghost lines may be visible as another variety of seam or sand split. A 
 very fine seam may be called a hair crack or hair seam. A lap seam, 
 lap, cold lap, or cold shut is produced when a fin or ridge is formed and 
 doubled over in forging or rolling. A snake or streak is a long wavy 
 seam. Longitudinal and transverse seams are those extending lengthwise 
 or crosswise respectively of the piece as produced. 
 
 (9.) Sliver. — A very thin piece of metal rolled into the surface of a 
 piece to which it is attached by only one end. 
 
 (10) Snake. — A variety of seam. (See seam.) 
 
 (b) Before acceptance careful examination of the surfaces of forgings 
 should be made to detect any of the foregoing defects. If ghost lines 
 exist report should be made to the Inspector in order that a special investi- 
 gation may be conducted to establish their extent. Forgings, made from 
 ingots cast in metal molds, are less likely to develop ghost lines than 
 those made from ingots cast in sand. The longer time the metal remains 
 liquid in the ingot mold the greater the segregation and possibility of 
 resulting ghost lines. Since the metal in ghost lines is usually softer 
 than the surrounding metal the streaks on the machined surface are some- 
 times slightly depressed below the general surface level. If a ghost 
 line contains considerable nonmetallic inclusions, however, it may be 
 so hard that the machine tool leaves a slight elevation at this line. If 
 the inclusions are present in sufficient number the chip during machining 
 may break at the ghost line. 
 
 11. INSPECTION OF FINISHED CRANK SHAFTS. 
 
 (a) A method which has been employed in the inspection of sub- 
 marine crank shafts and may be adapted to the inspection of any crank 
 shafts, is as follows: Support the shaft on V blocks of equal height placed 
 under the main bearings Nos. 2 and 7, the blocks resting upon a surface 
 
12 
 
 plate. Measurements should be made with a surface gauge to insure 
 that the shaft lies parallel with the surface plate and that there is ho- 
 tendency to sag. Steps should be taken to insure that this alignment 
 is maintained during subsequent inspection. The surface of the shaft 
 should then be carefully examined for all defects such as deep scratches, 
 small cracks, undercut fillet, etc., and the location of the oil holes should 
 be checked. 
 
 (b) Dimensions. — The length of each crank-pin bearing and main 
 bearing and the width and thickness of the webs and thickness' and 
 diameter of the flanges should be measured. The location and dimen- 
 sions of the keyways should then be checked. As the bolt holes in the 
 afterflange are drilled to a template furnished the manufacturer by the 
 contractor and are reamed to suit the reversing mechanism after assembly 
 these holes need be checked only as to location with respect to the crank 
 pins. The surfaces of the holes should be examined for possible defects 
 in the flange. The diameter of each crank pin and each bearing should 
 be measured by micrometer at points at right angles to each other for 
 variation in diameter, and for deviation from exact roundness. The 
 maximum variation in diameter rarely exceeds 0.002 inch. 
 
 (c) Inspection of throws. — The accuracy of the angles should be 
 checked by means of a dial guage graduated to 0.001 inch. The shaft 
 should be revolved until the parallel web surfaces of crank pin B, sketch 
 A, are exactly at right angles to the surface plate. This alignment 
 should be made with a machinist's square. The dial should then be 
 adjusted so that a reading taken when moving the guage over crank 
 pin A gives a reading of about 0.050 inch. Headings should then be 
 taken on crank pins 5, 3, and 4. These readings will probably be about 
 as follows: 0.042 inch, 0.056 inch, 0.061 inch. The shaft should then be 
 revolved until paralleled surfaces of crank webs C are exactly at right 
 angles to the surface plate, and without changing the gauge adjustment, 
 reading should be taken on crank pins 1, 6, 2, and 5. These readings 
 will probably be about as follows: 0.048 inch, 0.034 inch, 0.060 inch, 
 0.053 inch. The maximum error in angles is the difference between the 
 least reading and the greatest, which in the above case is 0.061—0.034 
 inch, which equals 0.027 inch. This method for checking the accuracy 
 of the angles of the throws requires that the web surfaces be parallel with 
 the planes passing through their respective pins and the journals. This 
 may be checked by placing each pair of pins in a position parallel with 
 the surface plate and by means of the surface guage determining that 
 the web surface is parallel also. 
 
 It is not practicable to determine that the web surfaces are parallel, or 
 if for any other reason it is desired, the following method may be em- 
 ployed: 
 
 The shaft should be revolved until the parallel web surfaces of crank 
 pin B, sketch A, are approximately at right angles to the surface plate. 
 A machinist's square may be used to obtain this alignment. The dial 
 should then be adjusted so that a reading taken when moving the gauge 
 over crank pin A, which is No. 2, gives a reading of about 0.050 inch. 
 The machinist's square should then be removed and the shaft revolved 
 sufficiently to cause the top of pin 2, and 3 corresponding to C, to lie in 
 the plane parallel with the surface plate. Readings of the gauge for pins 
 2 and 3 are taken, and for illustration assume these to be 0.056 inch and 
 the readings for pins 5 and 4 to be 0.042 inch and 0.061 inch, respectively. 
 
13 
 
 The shaft should then be revolved approximately 120°, and until pin 2 
 in its new position and with the adjustment of the gauge unchanged gives 
 a reading of 0.056 inch. Assume the reading of pins 1, 6, and 5 to be 
 0.048 inch and 0.070,^ respectively. In like manner pin 3 should be 
 revolved to the position indicated by A in the sketch, and in such a 
 position that the gauge, still at its original adjustment, registers 0.056 
 inch. The readings of pins 1 and 6 should then be made. These may 
 be assumed to be 0.053 inch and 0.048 inch, respectively. The maximum 
 error in angles is the difference between the least and the greatest read- 
 ings, which in the above case would be 0.070—0.042 inch, which equals 
 0.028 inch. 
 
 (d) Calculations. — The maximum error in angles is generally given in 
 degrees and is usually about 0.5°. _ In order to determine this value in 
 gauge readings in inches the following formula may be employed, assum- 
 ing: 
 
 R=Radius of throw, inches=7.0 
 
 D= Angle of pins, degrees= 120.0. 
 
 D / =Maximum angle of pins, degrees=120.5. 
 
 X= (cosine W — cosine D)XR. 
 In the above case the following results are obtained: 
 
 Cosine D'= cosine 120°.5=sine 30°. 5=0. 50754. 
 
 Cosine D=cosine 120°.0=sine 30°.0=0. 50000. 
 
 R=7.0inch. 
 
 X=0.00754X7.0=0.05278 inch or approximately 0.053 inch. 
 When the difference between the least and the greatest gauge reading 
 is less than 0.053 inch the error is less than 0.5°. The readings taken 
 before revolving the shaft show that angles "D" and "E " are equal but 
 do not show that they are 120°. Measuring angle "F," together with 
 "D" or "E, " proves that all the angles are appoximately 120°. 
 
 (e) Length, of stroke. — The throw of the crank should be measured 
 by a height gauge, the web being at right angles to the surface plate. 
 The error in stroke should be measured by revolving the shaft until the 
 parallel web surfaces of each of the pins A, B, and C are successively at 
 right angles to the surface plate, and then reading the gauge as shown in 
 sketch B. All readings should be taken with the same setting of the 
 gauge. The readings obtained will probably vary about as follows: 
 0.068, 0.059, 0.071, 0.078, 0.063, and 0.082 inch. The maximum error in 
 stroke is the difference between the least and greatest reading, which in 
 this case would be 
 
 0.082 inch -0.059 inch=0.023 inch. 
 
 The maximum error permitted in stroke is usually 0.030 inch. 
 
 (/) Variation of axes. — The variation of axis of any one main bearing 
 from the axis of shaft when measured by revolving shaft on V blocks 
 may be obtained by adjusting the dial gauge to the bearing under test, 
 revolving the shaft in the V blocks and noting the deflection of the gauge. 
 
 (g) Inspection of coupling bolts flanges, etc. — Submarine crank 
 shafts usually consist of two sections. After the above tests have been 
 made these sections are disconnected. The fit of the coupling bolts, 
 which is a driving fit, is indicated by the effort required to remove bolts. 
 After the section has been disconnected the surfaces of the coupling 
 flanges should be examined to discover evidences of piping, ghost lines, 
 etc. 
 
14 
 
 Surface of fay- 01/? fa£/e. 
 
 Shetch A 
 
 
 
 
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 S/te/ch B. 
 
15 
 
 12. INSPECTION OF HOLLOW-BORED SHAFTING. 
 
 (a) The dimensions of the shafts and bores are given in the contract or 
 order. Shafts are usually bored as follows: Line shafts are bored with 
 the large diameter extending nearly to the taper at the after end for the 
 outside coupling, and propeller shafts are bored with a large diameter 
 from the end upon which a collar about one and one-half times the 
 diameter of the shaft has been left, nearly to taper for the propeller hub. 
 The small holes at the tapered ends of the last two shafts are then bored 
 to meet the large holes. The small hole should be first bored smaller 
 than finished dimensions, say 2 inches diameter for a 3-inch hole, and the 
 shaft centered by the large hole, so that when the small hole is bored to 
 the required diameter it will be concentric with the large hole. Pro- 
 peller shafts are generally tapered at each end and therefore have small 
 holes within the taper. This is accomplished by, after boring the large 
 hole and the small hole in one end, heating the end of the shaft bearing 
 the collar and reducing the diameter of the collar by forging until the 
 hole is nearly closed. The small hole in this end is then bored in a 
 manner similar to the boring of the small hole in the oppposite end of 
 the same shaft. This closing in of the shaft end should in all cases pre- 
 cede final heat treatment and tests." 
 
 (6) Inspection of surface. — Upon the submission of the shafts, 
 finish machined or rough machined as required by the contract or order, 
 the shafts should be surface inspected for defects, and dimensions checked . 
 The diameters of rough machined shafts may be measured by means of 
 calipers. Diameter of finish machined shafts should be determined by 
 means of micrometers. 
 
 (c) Inspection of bore. — The bore should be carefully inspected for 
 uniformity, concentricity, defects, such as piping, etc., and to see that 
 the proper angle has been cut between the large and small bores. The 
 bores of propeller shafts should be inspected before closing in. After 
 completing the above inspection the hollow-bored shafts should be placed 
 in a lathe or on suitably designed rolls, measurements taken at ends of 
 the shaft to determine thickness of shaft walls, and the bore indicated 
 by means of suitably designed apparatus. The following are sketches of 
 apparatus which has been used for this purpose . 
 
 Description of sketch of electrical indicator. 
 
 The shaft, the bore of which is to be inspected, is placed in a lathe, chucked 
 at one end and supported near the other end by a carefully adjusted steady 
 rest, in such a manner as to cause the shaft to run true with the outside. 
 
 The indicating apparatus consists of a pipe 16 feet long and of sufficient 
 outside diameter to prevent sagging and small enough to pass through the 
 reduced bore of the shaft. One end of this pipe is clamped securely to a 
 u slide rest" and on the other end is attached a finger or lever. This lever is 
 so pivoted that it may be adjusted parallel with the pipe when passing through 
 the reduced bore, and can be made to assume a transverse position, shoivn 
 in the sketch, by means of a wire running through the pipe, the wire being 
 held taut and secured so as to hold the lever firmly fixed. 
 
 The tip of the lever is insulated from the pipe and an insulated wire runs 
 from this tip through the pipe to a switch of the lighting circuit. The other 
 side of the circuit is grounded to the lathe bed as shown, both switches being 
 closed when the apparatus is in use. 
 
16 
 
 The pipe is marked off On the outside every 2 feet, longitudinally from 
 the lever tip in its fixed position, so as to determine just where measurements 
 are taken; and the intermediate points are determined by a rule laid along 
 the pipe at the end of the shaft. With a 16-foot pipe, measurements can be 
 made up to about 14 feet inside the shaft. 
 
 By means of the slide rest, the apparatus is moved to any desired position 
 in the shaft, working first from one end and then the other end of the shaft, 
 if it is more than 14 feet long. The transverse feed of slide rest provides for 
 movement of the apparatus transversely , and as soon as lever tip touches 
 wall of the shaft, the electric lights shown in the circuit flicker or light up. 
 The travel of the lever tip should be in the horizontal plane of the axis of the 
 shaft for accurate measurements; but for practical purposes the eye is accurate 
 enough when adjusting the pipe in clamps of slide rest, with the free end of 
 pipe just entered in the shaft. Two scales are laid on transverse bed of slide 
 rest in order to measure the exact transverse movement of the apparatus. 
 
 Use of apparatus. 
 
 The different quadrants are indicated on the end of the shaft by the letters 
 "A," "B" "C," and "D"; apparatus being secured in proper position 
 in slide rest and moved into shaft to proper position for first measurements 
 of bore. The lever is then hauled back and secured in position. 
 
 With shaft slowly revolving, using transverse feed of slide rest, contact point 
 is moved until it touches the surface of the bore, when the lights in the circuit 
 will flash, indicating that a u high spot" has been touched. The point on the 
 circumference which has been touched is noted, and is indicated by a mark on 
 the end of the shaft, and the scale reading on slide rest is taken. Then the 
 shaft is turned so that the "high spot" detected is 180° from the contact point 
 of the lever. With the shaft fixed in position, the apparatus is again fed trans- 
 versely until the lights flash. The scale reading on the slide rest is again noted 
 and the difference between the two readings shows the movement of contact 
 point. One-half of this movement is the amount the axis of the bore is eccentric. 
 
 When more than a slight eccentricity is noted, careful measurements of the 
 bore should be taken, each 2 or 8 inches in length, and in each quadrant. 
 Ordinarily indications are made only every 2 feet of length. 
 
 Comment. 
 
 The above apparatus should only be used vohen the bore of the shaft has been 
 carefully searched with an electric torch and it has been found that the bore 
 has no serious defects or irregular cutting on the part of the boring tool. 
 Particularly with a shaft ivhich has "closea-in" ends the bore should be care- 
 fully examined before the ends have been closed in, since it is very difficult to 
 examine the bore through the small hole after the end is closed in, and in this 
 case the above apparatus might not show up a local flaw, hump, or spiral 
 groove in the bore. 
 
 When using the apparatus care must be taken not to start the 16-foot pipe 
 vibrating, as the free end will easily vibrate over an inch, and take a minute 
 or two to come back to rest. Also, moisture must be eliminated at the electric 
 contact point for accurate readings. 
 
 The apparatus appears accurate for measurement of eccentricity of the bore 
 at any desired point, provided the cross section at that point is a circle. If the 
 cross section is elliptical or otherwise irregular, it will be necessary, in order 
 to show up the true form of the bore, to take a large number of readings, which 
 would require a great deal of time. 
 
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 44498 
 
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 22o v. Lighting 
 
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 circuit 
 
 Lathe 
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 Ground 4-o 
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 Lathe 
 Steady rest- 
 
 Moving <srcra/e 
 
 Stationary 
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 ELECTRICAL INDICATOR 
 
 44498-21. (To face page 10.) 
 
 MECHfWICfiL mDICATOf? 
 

17 
 
 Mechanical indicator. 
 
 A sketch of a mechanical indicator which has been used is shown on the 
 opposite page. 
 
 (d) Tolerance in eccentricity. — In the absence of other instructions an 
 eccentricity of the axis of the large bore of rough machined shafts of ^ 
 inch and an eccentricity of the axis of the small or reduced bore of rough 
 machined shafts of Yt inch is generally permitted. A variation in wall 
 thickness measured at points 180° apart of the circumference corresponds 
 to twice the eccentricity of the axis of the bore. A variation in wall thick- 
 ness of Ye inch, measured 180° apart of a circumference, corresponds to ^ 
 inch eccentricity of the axis of the bore. The length of bores should con- 
 form to the requirements of the drawings, except for propeller shafts with 
 closed-in end. After boring it is impossible to forge down the open end 
 so that the taper and bore will exactly agree with the drawing. In no case 
 should the large bore extend farther than specified, since the shaft is 
 tapered for the coupling and the propeller, and the strength would thus 
 be impaired. The maximum length of the large bore should be that 
 shown on the drawing. 
 
 (e) Tolerance of diameter of bore. — The tolerance of diameter of bore 
 is usually stated on the blue print. The provisions of the General Speci- 
 fications for Machinery E3, May 1, 1919, in this regard are as follows: 
 "The tolerances in diameter of bore will be £ inch under size and -^ inch 
 over size." 
 
 (/) Straightening shafts.— Any working below forging heat should be 
 very carefully watched as initial stresses are liable to occur at the point 
 where bending is done. Shafts that have been warped or bent slightly 
 while undergoing heat treatment may be straightened by reheating to 
 not over 700° F. In case such forgings are heated over 700° F. complete 
 retests should be required. 
 
 13. FINAL INSPECTION. 
 
 (a) The assistant inspector must be assured by actual checking that 
 all dimensions are in accordance with the requirements of the specifica- 
 tions of the contract or order, and permitted tolerances, and that in the 
 case of rough-turned shafting there is sufficient metal for finish machin- 
 ing. Careful examination of all surfaces must be made for hair-line 
 cracks, streaks, and ghost lines. 
 
 14. SMALL FORGINGS. 
 
 The inspection of small forgings should be conducted in the same 
 manner as large forgings, except that tests may be taken to represent a 
 lot as defined by the specifications. Metal for test should be provided 
 by the manufacturer on several forgings in each lot in order that the 
 assistant inspector may select such forgings as he may desire from which 
 to obtain test specimens. In lieu of providing extra metal for testing, 
 the manufacturer may request the assistant inspector to select a forging 
 for test. 
 
18 
 
 15. STAMPING AND WEIGHING. 
 
 After final inspection has been completed and it has been determined 
 that the forging is in accordance with the requirements of the contract 
 or order it should be stamped "USN" and US ANCHOR adjacent to 
 the forging number. The forgings should also be stamped with identi- 
 fication numbers or letters if such are required by the order. Crank 
 shafts should be stamped on the face of one of the webs. Care should 
 be exercised that stamping of finished forgings is not done on bearing 
 surfaces. In all cases forgings should be weighed by the assistant in- 
 spector and note that weight was checked made on the Report of Mate- 
 rial Shipped. The assistant inspector should impress upon the manu- 
 facturer the importance of preparing and forwarding to the inspector's 
 office seven copies of "Report of Material Shipped" immediately ship- 
 ment is effected, in order that the material may be accepted at destina- 
 tion and payment promptly made. 
 
 CONCLUSION. 
 
 The foregoing is an outline of a procedure in the inspection of this 
 class of material. In general, since the contractors furnish the means 
 and the labor necessary to establish that their product is satisfactory, 
 their methods of checking dimensions, alignments, etc., should be em- 
 ployed, provided there be no reason to doubt the accuracy of the results 
 obtained thereby. The inspector has the right to recheck by his own 
 methods, but should exercise this right only in case conditions obtain 
 during inspection under the contractor's methods which render such 
 action advisable. 
 
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