Machines Tool

Gear Generating

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Gear Generating with Various Cutters

Figure 24.30 (a) Producing gear teeth on a blank by form cutting.

(b) Schematic illustration of gear generating with a pinion-shaped gear cutter.

(c) and (d) Gear generating on a gear shaper using a pinion-shaped cutter.

Note that the cutter reciprocates vertically. (e) Gear generating with rack-shaped cutter. Source: (d) Schafer Gear Works, Inc.

Hobbing

Figure 24.31 (a) Schematic illustration of gear cutting with a hob. (b) Production of worm gear through hobbing. Source: Courtesy of Schafer Gear Works, Inc.

Bevel Gears

Figure 24.32 (a) Cutting a straight bevel-gear blank with two cutter. (b) Cutting a helical bevel gear. Source: Courtesy of Schafer Gear Works, Inc.

Finishing Gears by Grinding

Figure 24.33 Finishing gears by grinding: (a) form grinding with shaped grinding wheels;

(b) grinding by generating with two wheels.

Types of Burs

Figure 24.28 Types of burs used in burring operations.

Involute Spur Gear

Figure 24.29 Nomenclature for an involute spur gear.

Gear Manufacturing Cost as a Function of Gear Quantity

Figure 24.34 Gear manufacturing cost as a function of gear quality. The numbers along the vertical lines indicate tolerances.

Broaching

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Broaching

Figure 24.20 (a) Typical parts made by internal broaching. (b) Parts made by surface broaching. Heavy lines indicate broached surfaces. (c) Vertical broaching machine. Source: (a) and (b) Courtesy of General Broach and Engineering Company. (c) Courtesy of Ty Miles, Inc.

Broach Geometry

Figure 24.21 (a) Cutting action of a broach showing various features. (b) Terminology for a broach.

Chip breaker Features on Broaches

Figure 24.22 Chip breaker features on (a) a flat broach and (b) a round broach.

Pull-Types Internal Broach

Figure 24.23 Terminology for a pull-type internal broach used for enlarging long holes.

Part with Internal Splines Made by Broaching

Figure 24.24 Example of a part with internal splines produced by broaching.

Sawing Operations

Figure 24.25 Examples of various sawing operations.

Saw Teeth

Figure 24.26(a) Terminology for saw teeth. (b) Types of tooth sets on saw teeth staggered to provide clearance for the saw blade to prevent binding during sawing.

Types of Milling Machine

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Column-and-Knee Type Milling Machines

Figure 24.15 Schematic illustration of (a) a horizontal-spindle column-and-knee type milling machine and (b) vertical-spindle column-and-knee type milling machine. Source: After G. Boothroyd.

CNC Vertical-Spindle Milling Machine

Figure 24.17 A computer numerical-control (CNC) vertical-spindle milling machine. This machine is one of the most versatile machine tools. The original vertical-spindle milling machine iused in job shops is still referred to as a “Bridgeport”, after its manufacturer in Bridgeport, Connecticut. Source: Courtesy of Bridgeport Machines Dibision, Textron Inc

Five-Axis Profile Milling Machine

Figure 24.18 Schematic illustration of a five-axis profile milling machine. Note that there are three principal linear and two angular movements of machine components.

Parts Made on a Planer

Figure 24,19 Typical parts that can be made on a planer

General Recommendations for Milling Operations

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General Recommendations for Milling Operations

Troubleshooting Guide for Milling Operations

Machined Surface Features in Face Milling

Figure 24.13 Machined surface features in face milling. See also Fig. 24.6.

Edge Defects in Face Milling

Figure 24.14 Edge defects in face milling: (a) burr formation along workpiece edge, (b) breakout along workpiece edge, and (c) how it can be avoided by increasing the lead angle (see also last row in Table 24.4).

Milling Cutter

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Face-Milling Cutter with Index able Inserts

Figure 24.5 A face-milling cutter with index able inserts. Source: Courtesy of Ingersoll Cutting Tool Company.

Effect of Insert Shape on Feed Marks on a Face-Milled Surface

Figure 24.6 Schematic illustration of the effect of insert shape on feed marks on a face-milled surface:

(a) small corner radius,

(b) corner flat on insert, and

(d) Feed marks due to various insert shapes.

Face-Milling Cutter

Figure 24.7 Terminology for a face-milling cutter.

Effect of Lead Angle on Undeformed Chip Thickness in Face Milling

Figure 24.8 The effect of the lead angle on the undeformed chip thickness in face milling. Note that as the lead angle increases, the chip thickness decreases, but the length of contact (i.e., chip width) increases. The edges of the insert must be sufficiently large to accommodate the contact length increase.

Position of Cutter and Insert in Face Milling

Figure 24.9 (a) Relative position of the cutter and insert as it first engages the workpiece in face milling.

(b) Insert positions towards the end of cut.

(c) Examples of exit angles of insert, showing desirable (positive or negative angle) and undesirable (zero angle) positions. In all figures, the cutter spindle is perpendicular to the page and rotates clockwise.

Ball Nose End Mills

Figure 24.10 Ball nose end mills. These cutters are able to produce elaborate contours and are often used in the machining of dies and molds. (See also Fig. 24.2d.) Source: Courtesy of Dijet, Inc.

Cutters

Figure 24.11 Cutters for (a) straddle milling, (b) form milling, (c) slotting, and (d) slitting with a milling cutter.

T-Slot Cutting and Shell Mill

Figure 24.12 (a) T-slot cutting with a milling cutter. (b) A shell mill.

Machining Processes

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Machining Processes Used to Produce

Various Shapes: Milling, Broaching, Sawing, and Filing; Gear Manufacturing .

Parts Made with Machining Processes

Milling Cutters and Milling Operations

Figure 24.2 Some basic types of milling cutters and milling operations. (a) Peripheral milling.

(b) Face milling. (c)

End milling. (d)

Ball-end mill with index able coated-carbide inserts machining a cavity in a die block.

(e) Milling a sculptured surface with an end mill, using a five-axis numerical control machine. Source:

(d) Courtesy of Iscar. (e) Courtesy of The Ingersoll Milling Machine Co.

Milling Operations

Figure 24.3 (a) Schematic illustration of conventional milling and climb milling. (b) lab-milling operation showing depth-of-cut, d; feed per tooth, f; chip depth-of-cut, tc; and workpiece speed, v.

Face-Milling Operation

Figure 24.4 Face-milling operation showing (a) action of an insert in face milling; (b) climb milling; (c) conventional milling; (d) dimensions in face milling. The width of cut, w, is not necessarily the same as the cutter radius.

Summary of Peripheral Milling Parameters and Formulas

Milling Machine Accessories

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• Milling Machine Accessories

• Wide variety of accessories greatly increase versatility and productivity

• Accessories classed as fixtures or attachments.

• Work-holding device fastened to table.

• Designed to hold work pieces that cannot be readily held in vise or when large quantities are to be machined.

• Milling Machine Attachments

• Designed to hold special attachment that increase versatility of machine.

• Vertical, high-speed, universal, rack milling, slotting.

• Designed to hold standard cutters.

• Arbors, collets, and adapters

• Designed to hold work piece.

• Vise, rotary table, indexing (dividing) head.

• Vertical Milling Attachment

• Enables plain or universal milling machine to be used as a vertical milling machine

• Mounted on face of column or over arm

• Angular surfaces made by swiveling head, parallel to face of column up to 45º either side of vertical

• Used for face milling, end milling, drilling, boring and T-slot milling

• Universal milling attachment modification allows swiveling in two planes for cutting compound angles

• Rack Milling Attachment

• Used to mill longer gear racks (flat gears) than could be cut with standard horizontal milling machine

• Rack indexing attachment included

• Slotting Attachment

• Converts rotary motion of spindle into reciprocating motion

• Cutting key ways, splines, templates, and irregularly shaped surfaces

• Length of stroke controlled by adjustable crank

• Tool slide may be swiveled to any angle in plane parallel to face of column.

• Arbors

• Arbors

• Used for mounting milling cutter

• Inserted and held in main spindle by draw bolt

• Shell-end mill arbors

• Permit face milling horizontally or vertically

• Fit into main spindle

• Collets and Adapters

• Collet adapters

• used for mounting drills or other tapered-shank tools in main spindle of machine or vertical milling attachment

• Quick-change adapter

• Mounted in spindle

• Permits such operations as drilling, boring, and milling without change in setup of work piece

• Arbors, Collets, and Adapters

• Milling Machine Vises

• Plain vise

• Jaws parallel or 90º to axis of spindle

Milling Machine Vises

• Swivel base vise

• Can swivel through 360º in horizontal plane

Milling Machine Vises

• Universal vise

• Can swivel through 360º in horizontal plane and tilted from 0º to 90 in vertical plane.

Indexing or Dividing Head

• Permits cutting of bolt heads, gear teeth, ratchets

• Revolve work as required to cut helical gears and flutes in drills, reamers, and other tools

• When connected to lead screw of milling machine

Horizontal Boring Mill

Horizontal Milling Machines and Accessories

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Horizontal Milling Machines

Manufacturing-type

•Cutter height is controlled by vertical movement of headstock

2. Special-type

• Designed for specific milling operations

3. Knee-and-column-type

• Relationship between cutter height and work controlled by vertical movement of table.

Manufacturing-Type

Used primarily for quantity production of identical parts •Distinctive features

•Automatic cycle of cutter and work approach

•Rapid movement during non-cutting cycle

•Automatic spindle stop.

Manufacturing-Type

Two common types

•Plain manufacturing type

•Small plain automatic knee and column type.

Plain Manufacturing Type Milling Machine

Special-Type Machines

•Designed for individual milling operations. •Used for only one particular type of job.

•Completely automatic

•Employed when hundreds or thousands of similar pieces are to be machined.

Machining Centers

•Capable of handling wide variety of work all in one setup.

•Straight and contour milling, drilling, reaming, tapping, and boring

Capable of high production rates while still maintaining high degree of accuracy.

•Rugged construction, reliable controls

•Anti-backlash ball screws.

Knee-and-Column-Type
Milling Machines

Machines in this class fall into three categories: •Plain horizontal milling machine.

•Universal horizontal milling machines.

•Vertical milling machines.

Universal Horizontal
Milling Machines

• Difference from plain horizontal machine is addition of table swivel housing.

• Located between table and saddle.

• Permits table to be swiveled 45º in either direction in a horizontal plane.

• Used for milling of helical grooves in twist drills, milling cutters, and gears.

Universal Horizontal Milling Machine

Milling Machine Parts

• Base

• Gives support and rigidity to machine.

• Acts as reservoir for cutting fluids.

• Column face

• Precision-machined and scraped section used to support and guide. knee when moved vertically.

• Knee

• Houses feed mechanism.

• Attached to column face and moved vertically.

• Saddle

• On top of knee

• Moved in or out by

Means of cross feed hand wheel (manually or automatically)

• Swivel table housing

• Fastened to saddle on universal milling machine.

• Enables table to be swiveled 45º either side of center line.

• Table

• Rests on guide ways in saddle and travels left and right

• Supports vise and work

• Cross feed hand wheel

• Used to move table in and out

• Table hand wheel

• Used to move table left and right

• Feed dial

• Used to regulate table feeds

• Spindle

• Provides drive for attachments, arbors, cutters

• Over arm

• Provides for correct alignment and support of arbor and various attachments

• Can be adjusted and locked in various positions.

• Arbor support

• Fitted to over arm and can be clamped

• Aligns and supports various attachments

• Elevating screw

• Gives upward or downward movement to knee and table (manually or automatically)

• Spindle speed dial

• Set by crank used to regulate spindle speed.

Backlash Eliminator

• Eliminates backlash (play) between nut and table lead screw

• Permits operation of climb (down) milling

• Two independent nuts mounted on lead screw

• Nuts engage common crown gear which meshes with rack

• Axial movement of rack controlled by backlash eliminator engaging knob on front of saddle

• Turning knob in, nuts forced to move along lead screw in opposite directions

Machine Backlash Eliminator