Machinery''''s Handbook 27th Episode 2 Part 3 pps

BROACHES AND BROACHING 955 BROACHES AND BROACHING The Broaching Process The broaching process may be applied in machining holes or other internal surfaces and also to many flat or other external surfaces. Internal broaching is applied in forming either symmetrical or irregular holes, grooves, or slots in machine parts, especially when the size or shape of the opening, or its length in proportion to diameter or width, make other machining processes impracticable. Broaching originally was utilized for such work as cutting keyways, machining round holes into square, hexagonal, or other shapes, forming splined holes, and for a large variety of other internal operations. The development of broaching machines and broaches finally resulted in extensive application of the process to external, flat, and other surfaces. Most external or surface broaching is done on machines of vertical design, but horizontal machines are also used for some classes of work. The broaching process is very rapid, accurate, and it leaves a finish of good quality. It is employed extensively in automotive and other plants where duplicate parts must be pro- duced in large quantities and for dimensions within small tolerances. Types of Broaches.—A number of typical broaches and the operations for which they are intended are shown by the diagrams, Fig. 1. Broach A produces a round-cornered, square hole. Prior to broaching square holes, it is usually the practice to drill a round hole having a diameter d somewhat larger than the width of the square. Hence, the sides are not com- pletely finished, but this unfinished part is not objectionable in most cases. In fact, this clearance space is an advantage during the broaching operation in that it serves as a chan- nel for the broaching lubricant; moreover, the broach has less metal to remove. Broach B is for finishing round holes. Broaching is superior to reaming for some classes of work, because the broach will hold its size for a much longer period, thus insuring greater accu- racy. Broaches C and D are for cutting single and double keyways, respectively. Broach C is of rectangular section and, when in use, slides through a guiding bushing which is inserted in the hole. Broach E is for forming four integral splines in a hub. The broach at F is for producing hexagonal holes. Rectangular holes are finished by broach G. The teeth on the sides of this broach are inclined in opposite directions, which has the following advan- tages: The broach is stronger than it would be if the teeth were opposite and parallel to each other; thin work cannot drop between the inclined teeth, as it tends to do when the teeth are at right angles, because at least two teeth are always cutting; the inclination in opposite directions neutralizes the lateral thrust. The teeth on the edges are staggered, the teeth on one side being midway between the teeth on the other edge, as shown by the dotted line. A double cut broach is shown at H. This type is for finishing, simultaneously, both sides f of a slot, and for similar work. Broach I is the style used for forming the teeth in internal gears. It is practically a series of gear-shaped cutters, the outside diameters of which gradually increase toward the finishing end of the broach, Broach J is for round holes but differs from style B in that it has a continuous helical cutting edge. Some prefer this form because it gives a shearing cut. Broach K is for cutting a series of helical grooves in a hub or bushing. In helical broaching, either the work or the broach is rotated to form the helical grooves as the broach is pulled through. In addition to the typical broaches shown in Fig. 1, many special designs are now in use for performing more complex operations. Two surfaces on opposite sides of a casting or forging are sometimes machined simultaneously by twin broaches and, in other cases, three or four broaches are drawn through a part at the same time, for finishing as many duplicate holes or surfaces. Notable developments have been made in the design of broaches for external or “surface” broaching. Burnishing Broach: This is a broach having teeth or projections which are rounded on the top instead of being provided with a cutting edge, as in the ordinary type of broach. The teeth are highly polished, the tool being used for broaching bearings and for operations on Machinery's Handbook 27th Edition Copyright 2004, Industrial Press, Inc., New York, NY BROACHING 957 Table 1. Designing Data for Surface Broaches Table 2. Broaching Pressure P for Use in Pitch Formula (2) The minimum pitch shown by Formula (1) is based upon the receiving capacity of the chip space. The minimum, however, should not be less than 0.2 inch unless a smaller pitch is required for exceptionally short cuts to provide at least two teeth in contact simulta- neously, with the part being broached. A reduction below 0.2 inch is seldom required in surface broaching but it may be necessary in connection with internal broaching. (1) Whether the minimum pitch may be used or not depends upon the power of the available machine. The factor F in the formula provides for the increase in volume as the material is broached into chips. If a broach has adjustable inserts for the finishing teeth, the pitch of the finishing teeth may be smaller than the pitch of the roughing teeth because of the smaller depth d of the cut. The higher value of F for finishing teeth prevents the pitch from becom- ing too small, so that the spirally curled chips will not be crowded into too small a space. Material to be Broached Depth of Cut per Tooth, Inch Face Angle or Rake, Degrees Clearance Angle, Degrees Roughing a a The lower depth-of-cut values for roughing are recommended when work is not very rigid, the tol- erance is small, a good finish is required, or length of cut is comparatively short. Finishing Roughing Finishing Steel, High Tensile Strength 0.0015–0.002 0.0005 10–12 1.5–3 0.5–1 Steel, Medium Tensile Strength 0.0025–0.005 0.0005 14–18 1.5–3 0.5–1 Cast Steel 0.0025–0.005 0.0005 10 1.53 0.5 Malleable Iron 0.0025–0.005 0.0005 7 1.5–3 0.5 Cast Iron, Soft 0.006 –0.010 0.0005 10–15 1.5–3 0.5 Cast Iron, Hard 0.003 –0.005 0.0005 5 1.5–3 0.5 Zinc Die Castings 0.005 –0.010 0.0010 12 b b In broaching these materials, smooth surfaces for tooth and chip spaces are especially recom- mended. 52 Cast Bronze 0.010 –0.025 0.0005 8 0 0 Wrought Aluminum Alloys 0.005 –0.010 0.0010 15 b 31 Cast Aluminum Alloys 0.005 –0.010 0.0010 12 b 31 Magnesium Die Castings 0.010 –0.015 0.0010 20 b 31 Material to be Broached Depth d of Cut per Tooth, Inch Pressure P, Side-cutting Broaches 0.024 0.010 0.004 0.002 0.001 Pressure P in Tons per Square Inch Steel, High Ten. Strength …… …250 312 200 004″cut Steel, Med. Ten. Strength ……158 185 243 143 006″ cut Cast Steel ……128 158 … 115 006″ cut Malleable Iron ……108 128 … 100 006″ cut Cast Iron … 115 115 143 … 115 020″ cut Cast Brass … 50 50 …… Brass, Hot Pressed … 85 85 …… Zinc Die Castings … 70 70 …… Cast Bronze 35 35 …… … Wrought Aluminum … 70 70 …… Cast Aluminum … 85 85 …… Magnesium Alloy 35 35 ……… Minimum pitch 3 LdF= Machinery's Handbook 27th Edition Copyright 2004, Industrial Press, Inc., New York, NY BROACHING 959 Terms Commonly Used in Broach Design Face Angle or Rake.—The face angle (see diagram) of broach teeth affects the chip flow and varies considerably for different materials. While there are some variations in practice, even for the same material, the angles given in the accompanying table are believed to rep- resent commonly used values. Some broach designers increase the rake angle for finishing teeth in order to improve the finish on the work. Clearance Angle.—The clearance angle (see illustration) for roughing steel varies from 1.5 to 3 degrees and for finishing steel from 0.5 to 1 degree. Some recommend the same clearance angles for cast iron and others, larger clearance angles varying from 2 to 4 or 5 degrees. Additional data will be found in Table 1. Land Width.—The width of the land usually is about 0.25 × pitch. It varies, however, from about one-fourth to one-third of the pitch. The land width is selected so as to obtain the proper balance between tooth strength and chip space. Depth of Broach Teeth.—The tooth depth as established experimentally and on the basis of experience, usually varies from about 0.37 to 0.40 of the pitch. This depth is measured radially from the cutting edge to the bottom of the tooth fillet. Radius of Tooth Fillet.—The “gullet” or bottom of the chip space between the teeth should have a rounded fillet to strengthen the broach, facilitate curling of the chips, and safeguard against cracking in connection with the hardening operation. One rule is to make the radius equal to one-fourth the pitch. Another is to make it equal 0.4 to 0.6 the tooth depth. A third method preferred by some broach designers is to make the radius equal one- third of the sum obtained by adding together the land width, one-half the tooth depth, and one-fourth of the pitch. Total Length of Broach.—After the depth of cut per tooth has been determined, the total amount of material to be removed by a broach is divided by this decimal to ascertain the number of cutting teeth required. This number of teeth multiplied by the pitch gives the length of the active portion of the broach. By adding to this dimension the distance over three or four straight teeth, the length of a pilot to be provided at the finishing end of the broach, and the length of a shank which must project through the work and the faceplate of the machine to the draw-head, the overall length of the broach is found. This calculated length is often greater than the stroke of the machine, or greater than is practical for a broach of the diameter required. In such cases, a set of broaches must be used. Chip Breakers.—The teeth of broaches frequently have rounded chip-breaking grooves located at intervals along the cutting edges. These grooves break up wide curling chips and prevent them from clogging the chip spaces, thus reducing the cutting pressure and strain on the broach. These chip-breaking grooves are on the roughing teeth only. They are stag- gered and applied to both round and flat or surface broaches. The grooves are formed by a round edged grinding wheel and usually vary in width from about 1 ⁄ 32 to 3 ⁄ 32 inch depending upon the size of broach. The more ductile the material, the wider the chip breaker grooves should be and the smaller the distance between them. Narrow slotting broaches may have the right- and left-hand corners of alternate teeth beveled to obtain chip-breaking action. Machinery's Handbook 27th Edition Copyright 2004, Industrial Press, Inc., New York, NY 960 BROACHING Shear Angle.—The teeth of surface broaches ordinarily are inclined so they are not at right angles to the broaching movement. The object of this inclination is to obtain a shear- ing cut which results in smoother cutting action and an improvement in surface finish. The shearing cut also tends to eliminate troublesome vibration. Shear angles for surface broaches are not suitable for broaching slots or any profiles that resist the outward move- ment of the chips. When the teeth are inclined, the fixture should be designed to resist the resulting thrusts unless it is practicable to incline the teeth of right- and left-hand sections in opposite directions to neutralize the thrust. The shear angle usually varies from 10 to 25 degrees. Types of Broaching Machines.—Broaching machines may be divided into horizontal and vertical designs, and they may be classified further according to the method of opera- tion, as, for example, whether a broach in a vertical machine is pulled up or pulled down in forcing it through the work. Horizontal machines usually pull the broach through the work in internal broaching but short rigid broaches may be pushed through. External surface broaching is also done on some machines of horizontal design, but usually vertical machines are employed for flat or other external broaching. Although parts usually are broached by traversing the broach itself, some machines are designed to hold the broach or broaches stationary during the actual broaching operation. This principle has been applied both to internal and surface broaching. Vertical Duplex Type: The vertical duplex type of surface broaching machine has two slides or rams which move in opposite directions and operate alternately. While the broach connected to one slide is moving downward on the cutting stroke, the other broach and slide is returning to the starting position, and this returning time is utilized for reloading the fixture on that side; consequently, the broaching operation is practically continuous. Each ram or slide may be equipped to perform a separate operation on the same part when two operations are required. Pull-up Type: Vertical hydraulically operated machines which pull the broach or broaches up through the work are used for internal broaching of holes of various shapes, for broaching bushings, splined holes, small internal gears, etc. A typical machine of this kind is so designed that all broach handling is done automatically. Pull-down Type: The various movements in the operating cycle of a hydraulic pull- down type of machine equipped with an automatic broach-handling slide, are the reverse of the pull-up type. The broaches for a pull-down type of machine have shanks on each end, there being an upper one for the broach-handling slide and a lower one for pulling through the work. Hydraulic Operation: Modern broaching machines, as a general rule, are operated hydraulically rather than by mechanical means. Hydraulic operation is efficient, flexible in the matter of speed adjustments, low in maintenance cost, and the “smooth” action required for fine precision finishing may be obtained. The hydraulic pressures required, which frequently are 800 to 1000 pounds per square inch, are obtained from a motor-driven pump forming part of the machine. The cutting speeds of broaching machines frequently are between 20 and 30 feet per minute, and the return speeds often are double the cutting speed, or higher, to reduce the idle period. Ball-Broaching.—Ball-broaching is a method of securing bushings, gears, or other com- ponents without the need for keys, pins, or splines. A series of axial grooves, separated by ridges, is formed in the bore of the workpiece by cold plastic deformation of the metal when a tool, having a row of three rotating balls around its periphery, is pressed through the parts. When the bushing is pressed into a broached bore, the ridges displace the softer material of the bushing into the grooves—thus securing the assembly. The balls can be made of high-carbon chromium steel or carbide, depending on the hardness of the compo- nent. Machinery's Handbook 27th Edition Copyright 2004, Industrial Press, Inc., New York, NY BROACHING 961 Broaching Difficulties.—The accompanying table has been compiled from information supplied by the National Broach and Machine Co. and presents some of the common broaching difficulties, their causes and means of correction. Causes of Broaching Difficulties Broaching Difficulty Possible Causes Stuck broach Insufficient machine capacity; dulled teeth; clogged chip gullets; failure of power during cutting stroke. To remove a stuck broach, workpiece and broach are removed from the machine as a unit; never try to back out broach by reversing machine. If broach does not loosen by tapping workpiece lightly and trying to slide it off its starting end, mount workpiece and broach in a lathe and turn down work- piece to the tool surface. Workpiece may be sawed longitudinally into sev- eral sections in order to free the broach. Check broach design, perhaps tooth relief (back off) angle is too small or depth of cut per tooth is too great. Galling and pickup Lack of homogeneity of material being broached—uneven hardness, porosity; improper or insufficient coolant; poor broach design, mutilated broach; dull broach; improperly sharpened broach; improperly designed or outworn fixtures. Good broach design will do away with possible chip build-up on tooth faces and excessive heating. Grinding of teeth should be accurate so that the correct gullet contour is maintained. Contour should be fair and smooth. Broach breakage Overloading; broach dullness; improper sharpening; interrupted cutting stroke; backing up broach with workpiece in fixture; allowing broach to pass entirely through guide hole; ill fitting and/or sharp edged key; crooked holes; untrue locating surface; excessive hardness of workpiece; insufficient clearance angle; sharp corners on pull end of broach. When grinding bevels on pull end of broach use wheel that is not too pointed. Chatter Too few teeth in cutting contact simultaneously; excessive hardness of material being broached; loose or poorly constructed tooling; surging of ram due to load variations. Chatter can be alleviated by changing the broaching speed, by using shear cutting teeth instead of right angle teeth, and by changing the coolant and the face and relief angles of the teeth. Drifting or misalignment of tool during cutting stroke Lack of proper alignment when broach is sharpened in grinding machine, which may be caused by dirt in the female center of the broach; inadequate support of broach during the cutting stroke, on a horizontal machine espe- cially; body diameter too small; cutting resistance variable around I.D. of hole due to lack of symmetry of surfaces to be cut; variations in hardness around I.D. of hole; too few teeth in cutting contact. Streaks in broached surface Lands too wide; presence of forging, casting or annealing scale; metal pickup; presence of grinding burrs and grinding and cleaning abrasives. Rings in the broached hole Due to surging resulting from uniform pitch of teeth; presence of sharpen- ing burrs on broach; tooth clearance angle too large; locating face not smooth or square; broach not supported for all cutting teeth passing through the work. The use of differential tooth spacing or shear cutting teeth helps in preventing surging. Sharpening burrs on a broach may be removed with a wood block. Machinery's Handbook 27th Edition Copyright 2004, Industrial Press, Inc., New York, NY 962 FILES AND BURS FILES AND BURS Files Definitions of File Terms.—The following file terms apply to hand files but not to rotary files and burs. Axis: Imaginary line extending the entire length of a file equidistant from faces and edges. Back: The convex side of a file having the same or similar cross-section as a half-round file. Bastard Cut: A grade of file coarseness between coarse and second cut of American pat- tern files and rasps. Blank: A file in any process of manufacture before being cut. Blunt: A file whose cross-sectional dimensions from point to tang remain unchanged. Coarse Cut: The coarsest of all American pattern file and rasp cuts. Coarseness: Term describing the relative number of teeth per unit length, the coarsest having the least number of file teeth per unit length; the smoothest, the most. American pattern files and rasps have four degrees of coarseness: coarse, bastard, second and smooth. Swiss pattern files usually have seven degrees of coarseness: 00, 0, 1, 2, 3, 4, 6 (from coarsest to smoothest). Curved tooth files have three degrees of coarseness: stan- dard, fine and smooth. Curved Cut: File teeth which are made in curved contour across the file blank. Cut: Term used to describe file teeth with respect to their coarseness or their character (single, double, rasp, curved, special). Double Cut: A file tooth arrangement formed by two series of cuts, namely the overcut followed, at an angle, by the upcut. Edge: Surface joining faces of a file. May have teeth or be smooth. Face: Widest cutting surface or surfaces that are used for filing. Heel or Shoulder: That portion of a file that abuts the tang. Hopped: A term used among file makers to represent a very wide skip or spacing between file teeth. Length: The distance from the heel to the point. Overcut: The first series of teeth put on a double-cut file. Point: The front end of a file; the end opposite the tang. Rasp Cut: A file tooth arrangement of round-topped teeth, usually not connected, that are formed individually by means of a narrow, punch-like tool. Re-cut: A worn-out file which has been re-cut and re-hardened after annealing and grinding off the old teeth. Safe Edge: An edge of a file that is made smooth or uncut, so that it will not injure that portion or surface of the workplace with which it may come in contact during filing. Second Cut: A grade of file coarseness between bastard and smooth of American pattern files and rasps. Set: To blunt the sharp edges or corners of file blanks before and after the overcut is made, in order to prevent weakness and breakage of the teeth along such edges or corners when the file is put to use. Shoulder or Heel: See Heel or Shoulder. Single Cut: A file tooth arrangement where the file teeth are composed of single unbro- ken rows of parallel teeth formed by a single series of cuts. Smooth Cut: An American pattern file and rasp cut that is smoother than second cut. Tang: The narrowed portion of a file which engages the handle. Upcut: The series of teeth superimposed on the overcut, and at an angle to it, on a double- cut file. Machinery's Handbook 27th Edition Copyright 2004, Industrial Press, Inc., New York, NY FILES AND BURS 963 File Characteristics.—Files are classified according to their shape or cross-section and according to the pitch or spacing of their teeth and the nature of the cut. Cross-section and Outline: The cross-section may be quadrangular, circular, triangular, or some special shape. The outline or contour may be tapered or blunt. In the former, the point is more or less reduced in width and thickness by a gradually narrowing section that extends for one-half to two-thirds of the length. In the latter the cross-section remains uni- form from tang to point. Cut: The character of the teeth is designated as single, double, rasp or curved. The single cut file (or float as the coarser cuts are sometimes called) has a single series of parallel teeth extending across the face of the file at an angle of from 45 to 85 degrees with the axis of the file. This angle depends upon the form of the file and the nature of the work for which it is intended. The single cut file is customarily used with a light pressure to produce a smooth finish. The double cut file has a multiplicity of small pointed teeth inclining toward the point of the file arranged in two series of diagonal rows that cross each other. For general work, the angle of the first series of rows is from 40 to 45 degrees and of the second from 70 to 80 degrees. For double cut finishing files the first series has an angle of about 30 degrees and the second, from 80 to 87 degrees. The second, or upcut, is almost always deeper than the first or overcut. Double cut files are usually employed, under heavier pressure, for fast metal removal and where a rougher finish is permissible. The rasp is formed by raising a series of individual rounded teeth from the surface of the file blank with a sharp narrow, punch-like cutting tool and is used with a relatively heavy pressure on soft substances for fast removal of material. The curved tooth file has teeth that are in the form of parallel arcs extending across the face of the file, the middle portion of each arc being closest to the point of the file. The teeth are usually single cut and are relatively coarse. They may be formed by steel displacement but are more commonly formed by milling. With reference to coarseness of cut the terms coarse, bastard, second and smooth cuts are used, the coarse or bastard files being used on the heavier classes of work and the second or smooth cut files for the finishing or more exacting work. These degrees of coarseness are only comparable when files of the same length are compared, as the number or teeth per inch of length decreases as the length of the file increases. The number of teeth per inch varies considerably for different sizes and shapes and for files of different makes. The coarseness range for the curved tooth files is given as standard, fine and smooth. In the case of Swiss pattern files, a series of numbers is used to designate coarseness instead of names; Nos. 00, 0, 1, 2, 3, 4 and 6 being the most common with No. 00 the coarsest and No. 6 the finest. Classes of Files.—There are five main classes of files: mill or saw files; machinists' files; curved tooth files; Swiss pattern files; and rasps. The first two classes are commonly referred to as American pattern files. Mill or Saw Files: These are used for sharpening mill or circular saws, large crosscut saws; for lathe work; for draw filing; for filing brass and bronze; and for smooth filing gen- erally. The number identifying the following files refers to the illustration in Fig. 1 1) Cantsaw files have an obtuse isosceles triangular section, a blunt outline, are single cut and are used for sharpening saws having “M”-shaped teeth and teeth of less than 60-degree angle; 2) Crosscut files have a narrow triangular section with short side rounded, a blunt outline, are single cut and are used to sharpen crosscut saws. The rounded portion is used to deepen the gullets of saw teeth and the sides are used to sharpen the teeth themselves. ; 3) Double ender fileshave a triangular section, are tapered from the middle to both ends, are tangless are single cut and are used reversibly for sharpening saws; 4) The mill file itself, is usually single cut, tapered in width, and often has two square cutting edges in addi- tion to the cutting sides. Either or both edges may be rounded, however, for filing the gul- Machinery's Handbook 27th Edition Copyright 2004, Industrial Press, Inc., New York, NY FILES AND BURS 965 flat, square, pillar, pillar narrow, half round and shell types. A special curved tooth file is available with teeth divided by long angular serrations. The teeth are cut in an “off center” arc. When moved across the work toward one edge of the file a fast cutting action is pro- vided; when moved toward the other edge, a smoothing action; thus the file is made to serve a dual purpose. Swiss Pattern Files: These are used by tool and die makers, model makers and delicate instrument parts finishers. They are made to closer tolerances than the conventional Amer- ican pattern files although with similar cross-sections. The points of the Swiss pattern files are smaller, the tapers are longer and they are available in much finer cuts. They are prima- rily finishing tools for removing burrs left from previous finishing operations truing up narrow grooves, notches and keyways, cleaning out corners and smoothing small parts. For very fine work, round and square handled needle files, available in numerous cross- sectional shapes in overall lengths from 4 to 7 3 ⁄ 4 inches, are used. Die sinkers use die sink- ers files and die sinkers rifflers. The files, also made in many different cross-sectional shapes, are 3 1 ⁄ 2 inches in length and are available in the cut Nos. 0, 1, 2, and 4. The rifflers are from 5 1 ⁄ 2 to 6 3 ⁄ 4 inches long, have cutting surfaces on either end, and come in numerous cross-sectional shapes in cut Nos. 0, 2, 3, 4 and 6. These rifflers are used by die makers for getting into corners, crevices, holes and contours of intricate dies and molds. Used in the same fashion as die sinkers rifflers, silversmiths rifflers, that have a much heavier cross- section, are available in lengths from 6 7 ⁄ 8 to 8 inches and in cuts Nos. 0, 1, 2, and 3. Blunt machine files in Cut Nos. 00, 0, and 2 for use in ordinary and bench filing machines are available in many different cross-sectional shapes, in lengths from 3 to 8 inches. Rasps: Rasps are employed for work on relatively soft substances such as wood, leather, and lead where fast removal or material is required. They come in rectangular and half round cross-sections, the latter with and without a sharp edge. Special Purpose Files: Falling under one of the preceding five classes of files, but modi- fied to meet the requirements of some particular function, are a number of special purpose files. The long angle lathe file is used for filing work that is rotating in a lathe. The long tooth angle provides a clean shear, eliminates drag or tear and is self-clearing. This file has safe or uncut edges to protect shoulders of the work which are not to be filed. The foundry file has especially sturdy teeth with heavy set edges for the snagging of castings—the removing of fins, sprues, and other projections. The die casting file has extra strong teeth on corners and edges as well as sides for working on die castings of magnesium, zinc, or aluminum alloys. A special file for stainless steel is designed to stand up under the abrasive action of stainless steel alloys. Aluminum rasps and files are designed to eliminate clog- ging. A special tooth construction is used in one type of aluminum tile which breaks up the filings, allows the file to clear itself and overcomes chatter. A brass file is designed so that with a little pressure the sharp, high-cut teeth bite deep while with less pressure, their short uncut angle produces a smoothing effect. The lead float has coarse, single cut teeth at almost right angles to the file axis. These shear away the metal under ordinary pressure and produce a smoothing effect under light pressure. The shear tooth file has a coarse single cut with a long angle for soft metals or alloys, plastics, hard rubber and wood. Chain saw files are designed to sharpen all types of chain saw teeth. These files come in round, rectangular, square and diamond-shaped sections. The round and square sectioned files have either double or single cut teeth, the rectangular files have single cut teeth and the diamond- shaped files have double cut teeth. Effectiveness of Rotary Files and Burs.—There it very little difference in the efficiency of rotary files or burs when used in electric tools and when used in air tools, provided the speeds have been reasonably well selected. Flexible-shaft and other machines used as a source of power for these tools have a limited number of speeds which govern the revolu- tions per minute at which the tools can be operated. Machinery's Handbook 27th Edition Copyright 2004, Industrial Press, Inc., New York, NY 966 FILES AND BURS The carbide bur may be used on hard or soft materials with equally good results. The principle difference in construction of the carbide bur is that its teeth or flutes are provided with a negative rather than a radial rake. Carbide burs are relatively brittle, and must be treated more carefully than ordinary burs. They should be kept cutting freely, in order to prevent too much pressure, which might result in crumbling of the cutting epics. At the same speeds, both high-speed steel and carbide burs remove approximately the same amount of metal. However, when carbide burs are used at their most efficient speeds, the rate of stock removal may be as much as four times that of ordinary burs. In certain cases, speeds much higher than those shown in the table can be used. It has been demon- strated that a carbide bur will last up to 100 times as long as a high-speed steel bur of corre- sponding size and shape. Approximate Speeds of Rotary Files and Burs As recommended by the Nicholson File Company. Steel Wool.—Steel wool is made by shaving thin layers of steel from wire. The wire is pulled, by special machinery built for the purpose, past cutting tools or through cutting dies which shave off chips from the outside. Steel wool consists of long, relatively strong, and resilient steel shavings having sharp edges. This characteristic renders it an excellent abra- sive. The fact that the cutting characteristics of steel wool vary with the size of the fiber, which is readily controlled in manufacture, has adapted it to many applications. Metals other than steel have been made into wool by the same processes as steel, and when so manufactured have the same general characteristics. Thus wool has been made from copper, lead, aluminum, bronze, brass, monel metal, and nickel. The wire from which steel wool is made may be produced by either the Bessemer, or the basic or acid open- hearth processes. It should contain from 0.10 to 0.20 per cent carbon; from 0.50 to 1.00 per cent manganese; from 0.020 to 0.090 per cent sulphur; from 0.050 to 0.120 per cent phos- phorus; and from 0.001 to 0.010 per cent silicon. When drawn on a standard tensile- strength testing machine, a sample of the steel should show an ultimate strength of not less than 120,000 pounds per square inch. Steel Wool Grades Tool Diam., Inches Medium Cut, High-Speed Steel Bur or File Carbide Bur Mild Steel Cast Iron Bronze Aluminum Magnesium Medium Cut Fine Cut Speed, Revolutions per Minute Any Material 1 ⁄ 8 4600 7000 15,000 20,000 30,000 45,000 30,000 1 ⁄ 4 3450 5250 11,250 15,000 22,500 30,000 20,000 3 ⁄ 8 2750 4200 9000 12,000 18,000 24,000 16,000 1 ⁄ 2 2300 3500 7500 10,000 15,000 20,000 13,350 5 ⁄ 8 2000 3100 6650 8900 13,350 18,000 12,000 3 ⁄ 4 1900 2900 6200 8300 12,400 16,000 10,650 7 ⁄ 8 1700 2600 5600 7500 11,250 14,500 9650 1 1600 2400 5150 6850 10,300 13,000 8650 1 1 ⁄ 8 1500 2300 4850 6500 9750 …… 1 1 ⁄ 4 1400 2100 4500 6000 9000 …… Description Grade Fiber Thickness Description Grade Fiber Thickness Inch Millimeter Inch Millimeter Super Fine 0000 0.001 0.025 Medium 1 0.0025 0.06 Extra Fine 000 0.0015 0.035 Medium Coarse 2 0.003 0.075 Very Fine 00 0.0018 0.04 Coarse 3 0.0035 0.09 Fine 0 0.002 0.05 Extra Coarse 4 0.004 0.10 Machinery's Handbook 27th Edition Copyright 2004, Industrial Press, Inc., New York, NY [...]... 122 1 End-feed Method 122 1 Automatic Centerless Method 122 1 Centerless Grinding 122 2 Surface Grinding 122 3 Principal Systems 122 5 Grinding Wheel Recommendations 122 6 Process Data for Surface Grinding 122 6 Basic Process Data 122 7 Faults and Possible Causes 122 9 122 9 122 9 122 9 1 23 0 1 23 0 1 23 0 1 23 0 1 23 3 1 23 3 1 23 3 1 23 4 1 23 4 1 23 5 1 23 5 1 23 5 1 23 5 1 23 6 1 23 6 1 23 7 1 23 7 1 23 7 1 23 8 1 23 8 1 23 8 1 23 8 1 23 8 1 23 9 1 23 9 1 23 9... 0. 920 63 0.770 32 0.97975 0.64087 1.00000 0.50000 0.97975 0 .35 9 13 0. 920 63 0 .22 968 0. 827 43 0. 122 13 0.70771 0.04518 0.57116 0.00509 28 Holes x1 y1 x2 y2 x3 0. 434 74 0.00 428 0 .30 866 0. 038 06 0.195 62 x1 y1 x2 y2 x3 0. 437 33 0.0 039 4 0 .31 594 0. 035 11 0 .20 611 x1 y1 x2 y2 x3 0. 439 73 0.0 036 5 0. 32 2 70 0.0 32 4 9 0 .21 597 x1 y1 x2 y2 x3 0.44195 0.0 033 8 0. 32 8 99 0. 030 15 0 .22 525 x1 y1 x2 y2 x3 0.444 02 0.0 031 4 0 .33 486 0. 028 06... y19 x20 y20 x21 y21 x 22 y 22 x 23 y 23 x24 y24 x25 y25 x26 y26 0.05 727 0.16844 0. 125 74 0.08851 0 .21 597 0.0 32 4 9 0. 32 2 70 0.0 036 5 0. 439 73 0.0 036 5 0.56 027 0.0 32 4 9 0.67 730 0.08851 0.784 03 0.16844 0.87 426 0 .26 764 0.9 427 3 0 .38 034 0.98547 0.50000 1.00000 0.61966 0.98547 0.7 32 3 6 0.9 427 3 0. 831 56 0.87 426 0.91149 0.784 03 0.96751 0.67 730 0.99 635 0.56 027 0.99 635 0. 439 73 0.96751 0. 32 2 70 0.91149 0 .21 597 0. 831 56 0. 125 74... y21 −0.11966 x 22 +0.4 427 3 y 22 −0 . 23 236 x 23 +0 .37 426 y 23 −0 .33 156 x24 +0 .28 4 03 y24 −0.41149 x25 +0.17 730 y25 −0.46751 x26 +0.06 027 y26 −0.49 635 27 Holes x4 −0 .36 369 y4 −0 .34 3 12 x5 −0. 433 01 y5 − 0 .25 000 x6 −0.47899 y6 −0.1 434 0 x7 −0.49915 y7 − 0. 029 07 x8 −0.4 924 0 y8 +0.086 82 x9 −0.45911 y9 +0.19804 x10 −0.40106 y10 +0 .29 858 x11 −0. 32 1 39 y11 +0 .38 3 02 x 12 −0 .22 440 y 12 +0.446 82 x 13 −0.11 531 y 13 +0.486 52. .. y19 x20 y20 x21 y21 x 22 y 22 x 23 y 23 x24 y24 x25 y25 x26 y26 x27 y27 x28 y28 28 Holes 0.14645 0.14645 0.07664 0 . 23 39 8 0. 028 06 0 .33 486 0.0 031 4 0.444 02 0.0 031 4 0.55598 0. 028 06 0.66514 0.07664 0.766 02 0.14645 0.8 535 5 0 . 23 39 8 0. 9 23 36 0 .33 486 0.97194 0.444 02 0.99686 0.55598 0.99686 0.66514 0.97194 0.766 02 0. 9 23 36 0.8 535 5 0.8 535 5 0. 9 23 36 0.766 02 0.97194 0.66514 0.99686 0.55598 0.99686 0.444 02 0.97194 0 .33 486... x15 +0.11 531 y15 +0.486 52 x16 +0 .22 440 y16 +0.446 82 x17 +0. 32 1 39 y17 +0 .38 3 02 x18 +0.40106 y18 + 0 .29 858 x19 +0.45911 y19 +0.19804 x20 +0.4 924 0 y20 +0.086 82 x21 +0.49915 y21 −0. 029 07 x 22 +0.47899 y 22 − 0.1 434 0 x 23 +0. 433 01 y 23 −0 .25 000 x24 +0 .36 369 y24 −0 .34 3 12 x25 +0 .27 475 y25 −0.41774 x26 +0.17101 y26 −0.46985 x27 +0.05805 y27 −0.496 62 28 Holes x4 −0 .35 355 y4 −0 .35 355 x5 −0. 4 23 36 y5 −0 .26 6 02 x6 −0.47194... −0. 4 23 36 y10 +0 .26 6 02 x11 −0 .35 355 y11 +0 .35 355 x 12 −0 .26 6 02 y 12 +0. 4 23 36 x 13 −0.16514 y 13 +0.47194 x14 −0.05598 y14 +0.49686 x15 +0.05598 y15 +0.49686 x16 +0.16514 y16 +0.47194 x17 +0 .26 6 02 y17 +0. 4 23 36 x18 +0 .35 355 y18 +0 .35 355 x19 +0. 4 23 36 y19 +0 .26 6 02 x20 +0.47194 y20 +0.16514 x21 +0.49686 y21 +0.05598 x 22 +0.49686 y 22 −0.05598 x 23 +0.47194 y 23 −0.16514 x24 +0. 4 23 36 y24 −0 .26 6 02 x25 +0 .35 355 y25... 0.4 626 3 0.96544 0 .31 733 0.890 92 0.18 826 0.78166 0.08688 0.64 738 0. 022 21 22 Holes x1 y1 x2 y2 x3 y3 x4 y4 x5 y5 x6 y6 x7 y7 x8 y8 x9 y9 x10 y10 x11 y11 x 12 y 12 x 13 y 13 x14 y14 x15 y15 x16 y16 x17 y17 x18 y18 x19 y19 x20 y20 x21 y21 x 22 y 22 0.50000 0.00000 0 .35 9 13 0. 020 25 0 .22 968 0.07 937 0. 122 13 0.1 725 7 0.04518 0 .29 229 0.00509 0. 428 84 0.00509 0.57116 0.04518 0.70771 0. 122 13 0. 827 43 0 .22 968 0. 920 63 0 .35 9 13. .. y19 x20 y20 x21 y21 x 22 y 22 x 23 y 23 x24 y24 x25 y25 x26 y26 x27 y27 27 Holes −0. 32 1 39 −0 .38 3 02 −0.40106 −0 .29 858 −0.45911 −0.19804 −0.4 924 0 −0.086 82 −0.49915 +0. 029 07 −0.47899 +0.1 434 0 −0. 433 01 +0 .25 000 −0 .36 369 +0 .34 3 12 −0 .27 475 +0.41774 −0.17101 +0.46985 −0.05805 +0.496 62 +0.05805 +0.496 62 +0.17101 +0.46985 +0 .27 475 +0.41774 +0 .36 369 +0 .34 3 12 +0. 433 01 +0 .25 000 +0.47899 +0.1 434 0 +0.49915 +0. 029 07... −0 .22 700 x5 −0.4 938 4 y5 −0.07 822 x6 −0.4 938 4 y6 +0.07 822 x7 −0.44550 y7 +0 .22 700 x8 −0 .35 355 y8 +0 .35 355 x9 −0 .22 700 y9 +0.44550 x10 −0.07 822 y10 +0.4 938 4 x11 +0.07 822 y11 +0.4 938 4 x 12 +0 .22 700 y 12 +0.44550 x 13 +0 .35 355 y 13 +0 .35 355 x14 +0.44550 y14 +0 .22 700 x15 +0.4 938 4 y15 +0.07 822 x16 +0.4 938 4 y16 −0.07 822 x17 +0.44550 y17 −0 .22 700 x18 +0 .35 355 y18 −0 .35 355 x19 +0 .22 700 y19 −0.44550 x20 +0.07 822 y20 . H-1 12- 22 1.750 H-1 12- 28 2. 125 H-1 12- 34 2. 500 H-1 12- 40 3. 000 H-1 12- 48 1 .39 06 to 1.7500 2. 250 2. 270 2. 265 2. 2 525 2. 2 521 1.000 0.094 2. 500 0 .37 5 H-144-16 1 .37 5 H-144 -22 1.750 H-144 -28 2. 125 H-144 -34 2. 500 H-144-40 3. 000. P-88-40 1.0156 to 1 .37 50 1.750 1.770 1.765 1.7 5 23 1.7519 1.000 0.094 P-1 12- 16 1 .37 5 P-1 12- 22 1.750 P-1 12- 28 2. 125 P-1 12- 34 2. 500 P-1 12- 40 3. 000 P-1 12- 48 1 .39 06 to 1.7500 2. 250 2. 270 2. 265 2. 2 525 2. 2 521 1.000 0.094 P-144-16 1 .37 5. 0.4075 0 .25 0 0. 031 P -26 -4 0 .3 12 P -26 -5 0 .37 5 P -26 -6 0.500 P -26 -8 0.750 P -26 - 12 1.000 P -26 -16 1 .37 5 P -26 -22 1.750 P -26 -28 0 .25 70 to 0 .3 125 0.500 0. 520 0.515 0.5017 0.5014 0 .3 12 0.047 P- 32 - 5 0 .37 5 P- 32 - 6 0.500