Mandrels

The standard lathe mandrel is a shaft or bar with 60 centers so that it may be mounted between centers. A workpiece is mounted on the mandrel for turning its outside surface true with the center hole. The mandrel is always rotated with a lathe dog it is never placed in a chuck for turning the workpiece. A straight lathe mandrel (Figure 6-34) is designed to fit the entire length of the center hole in the workpiece. A tapered mandrel (Figure 6-35) is used with parts that have a standard taper...

Band Saw Operation

When operating a band saw, there are some general principles that should be followed so that you will be able to select the blade with the proper pitch Small and thin-wall sections of metal require fine teeth. Large metal sections require the use of blades with coarse teeth so that adequate chip clearance is provided. Two teeth should be engaged in the metal to be cut at all times. Soft, easily machined metals require slightly coarser teeth to provide chip clearance. Hard metals of low...

Basic Construction

Because most horizontal boring machines are designed to machine large pieces of work, they usually have the various parts assembled on a heavy, substantial bed. The head is mounted on a vertical column or post at one end of the bed. The head post provides rigid support for the head in all operating positions. The entire head can be moved vertically on the ways of the column or head post (Figure 5-16). As the vertical position of the head is changed, the outboard bearing also moves up or down...

Power Hacksaws

A power hacksaw is an essential machine in most machine shop operations. For many years a hand-operated hacksaw was the only means for sawing off metal. Power-driven machines for driving metal-cutting saw blades have been developed to make the task easier. The power hacksaw can do the work much more rapidly and accurately. The machinist should be familiar with these machines, the blades used on the machines, and the operations performed on them. One type of power hacksaw commonly found in...

Taking the Cuts

The operator should decide on the number of cuts necessary, depending on the amount of metal to be removed. Usually, one or two roughing cuts and one or two finishing cuts are required, depending on the nature of the work and the finish desired. The ram should be positioned over the work and the cutting tool adjusted by the vertical feed handle so that it almost touches the work. By means of the hand cross-feed screw, move the table to the right or left (according to the cutting tool in use)...

Figure I 2 Power hacksaw blade

Straight cuts are made easily on power hacksaws. The vise is stationary, and the cut is made at a right angle to the sides of the stock. Most machines are equipped with an adjustable vise. Angular cuts at any desired angle up to 45 degrees can be made by swiveling the vise. To operate the power saw properly, the work should be fastened securely in the vise so that the blade will saw in the proper place. The blade will break if the work loosens in the vise. The saw blade should be lowered onto...

Summary

An indexing plate is a plate perforated with variously spaced holes arranged in concentric circles and is used in a milling or similar machine for dividing work (such as spacing out teeth in gear cutting). An index wheel is a circular wheel or disc graduated around its circumference for indicating the angular measurements through which it has been moved. It is used on dividing engines for testing or for adjusting the feed on lathes. A great variety of index plates are available for all indexing...

Drilling

The chief operation performed on the drill press is drilling, which is the removal of solid metal to form a circular hole. Prior to drilling a hole in metal, the hole is located by drawing two lines at right angles, and a center punch is used to make an indentation for the drill point at the center to aid the drill in getting started (Figure 4-1). Figure 4-1 Using the center punch. (A) Center punch used to make an indentation in the workpiece. (B) Indentation should be large enough for the...

Electrochemical Machining Process

Electrochemical machines are used for drilling, trepanning, and shaping extremely hard and tough materials (Figure 19-1). These machines may range from a small drill of the bench type to the larger automatic-cycle production machines. Figure 19-1 Electrochemical machine. (Courtesy Ex-Cell-0 Corp.) In the electrochemical machine, a low-voltage electric current is passed through a conductive fluid between the work and the tool electrode (see Figure 19-2). The fluid also flushes away the residue...

Speeds and Feeds

Speed and feed rates are governed by several variable factors material, cutter, width and depth of cut, required surface finish, machine rigidity and setup, power and speed available, and cutting fluid. Even though suggested rate tables are provided here, individual experience and judgment are extremely valuable in selecting correct milling speeds and feeds. The lower figure in the table for a given material should always be used until sufficient practical experience has been gained to change...

Index Plate Diagram

Diagram For Index Plate

An index plate can be used for any number of divisions that divides the number of holes in the plate equally. A plate with a larger number of holes than is required can be used if the number of holes is an exact multiple of the number of divisions required. In production work, it is safer to use a plate that has exactly the same number of holes as the required number because the possibility of making a mistake in indexing is reduced. Figure 14-1 shows the basic parts of an index plate that can...

Turning

The lathe, as the turning machine is commonly called, is the father of all machine tools. The principle of turning has been known since the dawn of civilization, probably originating as the potter's wheel. In the turning operation, the piece of metal to be machined is rotated and the cutting tool is advanced against it (Figure 2-10). WORK REVOLVES Figure 2-10 Turning. By contrast, the turret lathe is a lathe equipped with a multisided toolholder called a turret, to...

Size of Lathe

The maximum size of work that can be handled by the lathe is used to designate the size of the lathe (that is, the diameter and length of the work). Usually, the maximum diameter of the work is specified first, and the length is specified as the maximum distance between lathe centers (Figure 6-2). Manufacturers usually use the term swing to designate the size as the maximum diameter of the work that can be machined in the lathe. Thus, a 16-inch lathe indicates that the machine is designed to...

Abrasive Blasting

Abrasive blasting is used when a quality surface finish is not of primary importance. Abrasive material is blasted on metal surfaces with great force. Usually, abrasive blasting takes place in a blasting room, on tables, or in blasting cabinets. The use of respirators is required for blasting in blasting rooms. (A) On cylindrical pieces. (B) On flat pieces. Figure 18-12 Types of grinding commonly performed on external, internal, and flat work. Centerless grinding, either external or internal,...

Safety Precautions

First, the operator should understand thoroughly the construction and operating action of the machine before attempting its operation. This is important not only for the operation but also because it lessens the chances of the machine itself being damaged seriously. The following suggestions by Brown and Sharpe Manufacturing Company should be carefully noted and remembered Do not move an operating lever without knowing in advance the action that is going to take place. Never toy with the...

Setup of Dividing Head and Driving Mechanism

The following instructions for setting up the dividing head and driving mechanism should be followed in order 1. The table of the milling machine and the bottoms of the dividing head and tailstock should be cleaned. 2. Clamp the headstock of the dividing head in the center slot of the table, in a location suitable for the work. 3. Check the spindle of the dividing head with a test bar and indicator to be certain that it is parallel to the table. 4. Depending on the length of the work, clamp the...

Extra Fine Thread Series UNEF

This series can be used in most conditions applicable for fine threads. It is used where even finer threads are desirable, as for thin-walled tubes, couplings, nuts, or ferrules (see Table 8-3). The mechanic or machinist should become familiar with the following terms commonly used in connection with screw thread systems and thread-cutting operations Allowance A prescribed difference between the dimensions of mating parts. Maximum allowance is the difference Table 8-2 Fine-Thread Series, UNF,...

Holding and Driving the Work

A number of work-holding devices are used to hold or support the workpiece securely for the different lathe operations. A number of different devices are also used as toolholders. Some workpieces must be held and rotated by chucks depending on the size, shape, and operation to be performed. The chucks are attached to the headstock spindle of the lathe. Figure 6-17 Quick-change gearbox. A wide range of feeds and threads per inch can be selected. (Courtesy Cincinnati Milacron Co.) Figure 6-17...

Milling Machine Dividing Heads

The dividing head (also called an index head) is a device that can be used to rotate a piece of work through given angles usually equal divisions of a circle. A dividing head, in combination with the longitudinal feeding movement of the table, is used to impart a rotary motion to a workpiece for helical milling action, such as in milling the helical flutes of cutters. Dividing heads are used in milling operations whenever it is necessary to divide a circle into two or more parts (Figure 13-1)....

Spot Facing Operation

Another operation similar to counterboring is the spot-facing operation (Figure 4-29). Just enough metal is removed to provide a bearing surface for a washer, nut, or the head of a cap screw. The spot-facing tool should be mounted in the drill press spindle, and the pilot of the spot-facing tool should be aligned with the original drilled hole (Figure 4-30). Figure 4-24 Older type of motor reversing mechanism used for taps Vi inch to I inch in diameter. A magnetic reversing control, actuated by...

Drilling and Boring

Drilling is a basic machine shop operation dating back to primitive humans. It consists of cutting a round hole by means of a rotating drill (Figure 2-9). Boring, on the other hand, involves the finishing of a hole already drilled or cored. This is accomplished by means of a rotating, offset, single-point tool that somewhat resembles the tool used in a lathe or a planer. The tool is stationary and the work revolves on some boring machines. On other types of boring machines, the reverse is true....

Formula Differential Indexing 69 Teeth With Examples

Diagram The Index Plate

As the worm-spindle ratio is 40 to 1, Note that in negative compounding, the movements are in opposite directions (Figure 14-5). Move the index crank one hole in the 19-hole circle. Disengage the stop pin and rotate the index plate one hole in the opposite direction in the 20-hole circle. The resultant rotation of the worm is as follows Figure 14-5 Basic diagram of an index plate, showing negative compounding. Figure 14-5 Basic diagram of an index plate, showing negative compounding. The...

Thread Cutting Operations

Floating Carriage Micrometer Diagrams

The Sharp-V thread is used as an example for thread cutting. If a change-gear lathe is used, the change gears should be properly in mesh, and the operator should note the following For right-hand threads, the carriage must travel toward the headstock. For left-hand threads, the carriage must travel toward the tail-stock. Reversing the direction of rotation of the lead screw (by shifting the tumbler gears) will cause the carriage to move in the opposite direction, without changing the direction...

Superprecision Turret Lathes

The bench turret lathe operates in much the same manner as the larger turret lathes. This type of machine tool is designed for short-run and long-run superprecision secondary machining operations that require extremely close tolerances. Figures 10-11 through 10-39 illustrate the bench turret lathe, as well as a wide variety of features, attachments, and operations performed on this precision machine tool. Figure 10-9 Taper attachment for the universal carriage. Figure 10-9 Taper attachment for...

Preliminary Operations

The various duties of the milling machine operator can be classified as preliminary operations and machining operations. Several preliminary operations are necessary before the machine can be started. Cleaning of the milling machine cannot be emphasized too strongly. The machine should be cleaned both before and after using. Accuracy and durability of the machine depend on its being kept clean this applies to all machine tools. If a milling machine is cleaned as soon as possible after use, it...

Automatic Feed Stops

Automatic devices that disconnect the power feed after a predetermined distance of travel are often used on lathes in production work. These devices can be used to enable a single machinist to operate two or more lathes simultaneously. The operator can place the work in a lathe, engage the power feed for a cut, and proceed to the next lathe. When the end of the cut is reached, the power feed is automatically disconnected. The micrometer carriage stop is especially desirable for production work...

Vertical Boring Mills and Horizontal Boring Machines

The vertical boring mill is virtually equivalent to a lathe turned on end so that the faceplate is horizontal, omitting the tailstock. The table of the boring mill corresponds to the faceplate of the lathe. It is more convenient to clamp heavy work to the horizontal table of the mill than to the vertical faceplate of the lathe. Although the vertical boring machine is adapted to boring and turning operations on work that has a diameter or width greater in proportion than its length, the...

Thread Cutting Tools

The shape of the cutting tool depends on the type of thread to be cut. The tool must be ground and set accurately, or the correct thread form will not be tolerated. Various gauges are available that can be used as guides in grinding. The shape of the cutting tool for cutting a Sharp-V 60 thread is shown in Figure 8-13. Sometimes the point is not ground off, and the thread is cut with the Sharp-V bottom (obsolete) this should never be done when maximum strength is desired. The Acme screw thread...

Holding Devices

Drill presses and drilling machines require two types of holding devices devices for holding the tool or cutter, and devices that secure the workpiece in a properly mounted position for drilling, tapping, and so forth. Most cutting tools have either a straight shank or a taper shank. Most drill presses are equipped with a Morse taper spindle. Straight-shank drills are held in a chuck. Many styles of chucks for a variety of purposes are manufactured (Figure 4-33 and Figure 4-34). The drill press...

Table Drive

Open And Cross Belt Drive Mechanism

The table drive of a planer can be obtained by one of three methods Figure 16-4 shows a basic diagram illustrating the rack-and-spur-gear method with belt-pulley drive. Figure 16-4 Diagram of rack-and-spur-gear table drive mechanism. When the drive mechanism is made up entirely of gears, a large gear known as a bull gear is connected to a rack on the bottom side of the table and to an electric motor by a series of gears. The quick return of the planer table is accomplished by adjustable stops...

Slotter Cutting Tools

Slotter Tools

As the cutting motion of a slotter is vertical (rather than horizontal), slotter cutting tools differ from shaper and planer tools. The cutting edge is formed on the end of the cutting tool. This is so that it is placed under compression and will cut when pushed endwise. The cutting face that turns the shaving is on the end of the tool (Figure 17-10). The horizontal axis (AB in Figure 17-10) is parallel with the table and perpendicular to the vertical axis (CD in Figure 17-10). The clearance...

Change Gear Calculations

Lathe Gear Changing

In the absence of an index chart showing gear combinations for various threads, it is necessary to calculate the proper gears to use for cutting threads. On lathes equipped with tumbler reverse gears, it must first be determined whether the lathe is even-geared or odd-geared. On an even-geared lathe, the stud gear revolves at the same speed as the spindle gear (that is, the two gears are equal in size). If the stud gear revolves at any other speed, the lathe is an odd-geared lathe. Change gears...

Countersinking

The operation in which a cone-shaped enlargement is formed at the end of a hole is called countersinking. A conical cutting or reaming tool is used to taper or bevel the end of the hole (Figure 4-27). The countersinking operation involves fastening the workpiece properly, mounting the countersink in the drill chuck, aligning the countersink with the work, selecting the correct spindle speed, and using care in feeding the countersink to the work. The countersink should be rotated at a relatively...

Radial Drill Press

In a radial drill press (Figure 3-9), the vertical spindle can be positioned horizontally and locked on an arm that can be swiveled about, and raised and lowered on a vertical column. Thus, the spindle can be placed in any position within its range. The various arm and spindle movements are shown in Figure 3-10. Some radial drills do not have the last two movements illustrated. Because the drilling head is moveable to any position, it is not necessary to move heavy work for each hole that is to...

Spindle

It is usually splined and made of alloy steel. The spindle rotates and moves up and down in a quill or sleeve, which slides on bearings. A pinion engages a rack fastened to the quill to provide vertical movement of the quill, permitting the Figure 3-1 Bench-type sensitive drill press. (Courtesy Buffalo Forge.) twist drill to be either fed into or withdrawn from the workpiece. A typical spindle assembly is shown in Figure 3-4. Spindle speed is controlled on...

Classification

Boring mills are used for various purposes drilling, reaming, chamfering, counterboring, and so on. They can be classified by the number of rams (either single ram or double ram), and they are available as either single- or double-station units (Figure 5-1). Vertical boring mills are easy to load, especially for handling awkward parts. All stations are readily accessible front stations, making it easy for one operator to handle several machines. The Figure 5-1 A vertical boring machine....

Basic Construction and Classification

The milling machine has a power-driven spindle. An arbor for holding multitooth cutters fits into the spindle. The cutting edges or teeth on revolving circular cutters remove a controlled amount of metal at each revolution of the cutter. The workpiece is mounted on a movable table and is fed against the cutter. The table can be moved either by hand-feed or by power-feed. When several cutters are mounted on the arbor, several surfaces can be machined in one operation. The knee-and-column type of...

Lathe Centers

Included Angle For Lathe Centers

The live center is stationary in the main spindle of the headstock. It is called live because it turns with the workpiece. The dead center is placed in the tailstock spindle, and it does not rotate with the workpiece hence the term dead center . The live center does not have to be hardened because it rotates with the work. The dead center must be hardened because it does not rotate and must withstand the friction of the workpiece against it. Hardened centers are usually indicated by grooves cut...

Holding the Work

As shaper operations are concerned primarily with small work-pieces, the work is usually held in either a vise or a chuck. These holding devices are auxiliary to the table or machine. It is important to place the stops T-bolts properly. If the work were laid on the table without the stops to resist the thrust of the cutting tool on the cutting stroke, the cutting tool would push the work rather than cut it. Large pieces of work that cannot be held in a vise should be fastened to the table. In...

Stroke Adjustment

The ram should be adjusted to provide the proper length of stroke and to provide the proper position of travel over the workpiece. The stroke adjustment screw see Figure 15-2 can be turned to produce either a shorter or a longer stroke. A handle is provided on most machines for the square head of the adjusting screw. Unless the operator is familiar with the machine, trial and error can determine the direction of turning the stroke adjustment screw for either a longer or a shorter stroke. The...

Milling Machines Sector

Plain Indexing Head

The types of dividing heads used on milling machines are plain, universal, and helical. Dividing heads can also be classified as to size for example, the Cincinnati Milacron Company dividing head is available in three different sizes . The basic parts of a plain dividing head are shown in Figure 13-2 and Figure 13-3. In a plain dividing head, the spindle rotates about a horizontal axis. The principal parts of the dividing head are spindle, worm wheel, worm, index plate, index pin, and sector....

Slotter Operations

Slotter Tool Figure

Workpieces that are to be machined on the bottom side cannot be mounted directly on the table surface but should be mounted on parallel strips to give clearance for the cutting tool Figure 17-2 . The height A of the parallel should be a large enough distance to provide work clearance. Since workpieces that are to be machined on the bottom side cannot be mounted directly on the table surface Figure 17-2 Proper clearances for a cutting tool, work and table. Figure 17-2 Proper clearances for a...