Turning Operations

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Turning Operations

Lec4-1Fundamentals of machining and machine tools - Isfahan Uni. of Tech.

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Turning Operations

• Longitudinal turning

• Facing

• Knurling

• Boring

• Taper Turning

• Eccentric Turning

• Chamfering

• Cut-off

• Grooving

• Contour turning

• Grinding

• Threading

Fundamentals of machining and machine tools - Isfahan Uni. of Tech.

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Turning Operations

Facing Taper turningContour turning

Form turning

Chamfering Cutoff Threading

Boring Drilling Knurling


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Longitudinal Turning


http://www.youtube.com/watch?gl=HK&hl=zh-TW&v=Tc-MKmfMnqw&feature=related

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tool

5


• Small overhang

• Tool offset

• Easier cutting, less vibration and noise

• h=0.04 x R

• hmax=0.5 mm

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tool

h R


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• Main cutting edge

• Right hand

• Left hand

• Neutral

Right-hand Left-handneutral


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Facing

• Feed in the radial direction

• Tool tip on the workpiece center

• Direction of tool motion depends on the main cutting edge


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Facing


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Knurling

• Regularly shaped roughness on cylindrical surfaces

• For Decorative and/or Functional Purpose

• Knurling Tool

• A Forming Process

• MRR~0

• Too much heat -> coolant

• Workpiece diameter increases


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Knurling


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Knurling


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Knurling


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Taper

• Rapid and accurate method of aligning machine parts

• Easy method of holding tools

• Taper is expressed as change of diameter per unit of length

• Inch system usually expressed in taper per foot (tpf)

D=inch , d=inch , L=inch

L

dD

k

1

L

D d α

L

dDtpf

.12


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Taper Calculations: TPF

in per foot

L

dDtpf

12

1 3

1 1.250tpf

.12


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Metric Tapers

• Expressed as ratio of 1 mm per unit of length

Work would taper 1 mmin a distance of 20 mm

ratio of 1:20


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Machine Tapers

• Classified by American Standards Association

• Self-holding tapers

• Steep or self-releasing tapers


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Self-Holding Tapers

• Remain tight in position

• Most common forms

• Morse, the Brown & Sharpe, .750-in.-per-ft taper

• Smaller sizes provided with tang to help drive the cutting tool

• Larger sizes employ tang drive with shank held in by key or key drive with shank held draw bolt


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Steep Tapers

• 3.500 in. taper per foot (tpf)

• Formerly called standard milling machine taper

• Used mainly for alignment of milling machine arbors and accessories

• Has key drive and uses draw-in bolt to hold it securely in milling machine spindle


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Standard Tapers

• Morse taper• Approximately 0.625-in tpf, eight sizes #0 to #7

• Used for drills, reamers, and lathe center shanks

• Brown & Sharpe taper• 0.502-in. tpf, sizes from #4 to #12

• Used on Brown and Sharpe machines

• Jarno taper• 0.600-in. tpf, sizes from #2 to #20

• Standard taper pins• Used for positioning and holding parts together

• ¼ tpf, standard sizes range from #6/0 to #10


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Taper Turning

• Swiveling the compound rest

• Offsetting tailstock

• Taper attachment

• Method used depends on work length, taper length, taper angle and number of pieces


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Taper Turning Using Compound Rest

1. Calculate the taper angle

2. Loosen compound rest lock screws

3. Swivel compound rest as follows:


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4. Tighten compound rest lock screws

5. Set cutting tool to center with toolholder at right angles to taper to be cut

6. Tighten tool-post securely

7. Back off top slide of compound rest so there will be enough travel to machine length of taper


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8. Move carriage to position cutting tool near start of taper and then lock carriage

9. Rough turn taper by feeding cutting tool using compound rest feed handle

10.Check taper for accuracy and read just compound rest setting if necessary

11.Finish-turn and check taper for size and fit


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• Short or large angle tapers

• Tool fed by hand -> not very good surface finish

• Internal and external tapers

• Angle

• Tapered mandrels

• Reading on the machine


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Taper Turning Using Tailsotck Offset

• Loosen the tailstock clamp nut

• Offset upper part of tailstock by loosening the screw

S

lα/2

l

dD

2)

2tan(

2

dDS

l

S)

2sin(

Small angle


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l

dD

2)

2tan(

L

S)

2sin(

l

dDLS

2

Small angle

50max

LS


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• Generally used when no taper attachment available

• Involves moving tailstock center out of line with headstock center

• Amount tailstock may be offset limited

• Small taper angles (<3°)

• Only external tapers

• Time consuming


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Taper Turning Using Taper Attachments

• The amount guide bar set over is one-half angle given on drawing

• Cross slide is attached to guide bar

• Remove binding screw that holds cross-slide to cross-feed screw nut


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• Simple setup

• Easy to change from taper to parallel turning with no time lost to align centers

• No limit on the work length

• Lathe centers remain in alignment, preventing distortion of centers

• Work can be tightly held between centers, in chuck or in collet

• Internal and external

• Automatic feed -> good surface finish


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Eccentrics

• Shaft that may have two or more turned diameters parallel to each other

• Not concentric with normal axis of work

• Used in locking devices, in feed mechanism on some machines, and in crankshaft of automobiles

• Where necessary to convert rotary motion into reciprocating motion


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Eccentrics

• Amount of eccentricity (throw) is distance set of center holes has been offset from normal work axis

• If center holes offset .250 in. from work axis, amount of throw would be .250 in and total travel of eccentric would be .500 in.


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Eccentric Turning

• Adjustable three-jaws chuck


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Eccentric Turning

• Auxiliary part

• Fixture

• Faceplate


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Eccentric Turning

• Mandrel for hollow shafts


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Procedure to Turn Eccentric

1. Place work in chuck and face it to length

2. Place work in V-block on surface plate

3. Set vernier height gage to top of work and note reading

4. Subtract half work diameter from reading and set gage to this dimension

5. Scribe centerline on both ends of work

6. Rotate work 90° and scribe another centerline on both ends at same height-gage setting


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7. Lower or raise height-gage as much as the amount of eccentricity and scribe lines for offset centers on both ends

8. Carefully center-punch four scribed centers and drill center holes in each end

9. Mount work in lathe and turn diameter with true centers

10.Set work on offset centers and turn eccentric (center section) to required diameter


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Eccentric Turning


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Eccentric Turning


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Chamfering

• Cutting edge cuts an angle on the corner of the cylinder, forming a "chamfer"


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Grooving

• Tool feed in the radial direction

• Groove width equal to cutting tool width

• Multiple cuts for grooves larger than the tool width

• Internal and external


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Grooving


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Grooving


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Parting-off

• Similar to grooving

• Tool in the radial direction


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Parting-off


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Threading

• Pointed form tool

• Axial feed

• Large feed rate

• Specified length and pitch

• May require multiple passes

• Will be later discussed in detail


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Threading


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Contour Turning

• Tool follows a contour that is other than straight

• Contour attachment

• Copying lathe


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Drilling

• Drill is fixed in the tailstock

• Workpiece rotates

• Tailstock hand-wheel is used to feed the drill


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Drilling

1. Center drill


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Drilling

2. Twist drill


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Boring

• Axial feed of boring tool

• Along an internal surface

• Form different features, such as steps, tapers, chamfers, and contours

• After drilling a hole


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Reaming

• Reamer is fixed in the tailstock and fed axially


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Tapping

• Tap is fixed in the tailstock and moved along the workpiece axis


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Sequence of Operations to Turn a Pin


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Sequence of Operations to Turn a Pin


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Some Advanced Turning Techniques


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MDT

• Multi Direction Turning

• Turning

• Profiling

• Grooving

• Threading

• Parting-off


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MDT

• Applications


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MDT


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MDT

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2

3

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MDT


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Plunge Turning

• Saving time

• Improve surface integrity

Conventional Turning Plunge Turning


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Plunging

Single point Plunge

• Potential with Plunge- High productivity

- Improved surface integrity

• Limitation with Plunge- Dimensional & form accuracy

- Flexibility

- No standard solution


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Capto


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Capto

• Quick tool change

• Flexible

• Modular


Turning Operations

Documents

Transcript of Turning Operations