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Mounting, Removing, and Aligning Lathe Centers

Session 8

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Lathe Centers

• Work machined between centers is turned for some portion of length, then reversed, and other end finished

• Critical when machining work between centers that live center be absolutely true

• Produces concentric diameters

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Mounting Lathe Centers• Remove any burrs from lathe spindle,

centers, or spindle sleeves• Clean tapers on lathe centers and in

headstock and tailstock spindles• Partially insert cleaned center in lathe

spindle• Force center into spindle

• Follow same procedure when mounting tailstock center

• Check trueness of center• Use dial indicator

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Removing Lathe Centers• Live center

• Use knockout bar pushed through headstock spindle (slight tap)

• Use cloth over center and hold to prevent damage

• Dead center• Turn tailstock handwheel to draw spindle

back into tailstock• End of screw contacts end of dead center, forcing

it out of spindle

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Alignment of Lathe CentersWhen lathe center aligned Parallel

diameters produced

Three common methods used to align1. Aligning tailstock

2. Trial Cut

3. Test Bar and Indicator

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Alignment of Lathe CentersAligning Tailstock• Aligning centerlines

on back of tailstock with each other

• Only a visual checkand not too accurate

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Alignment of Lathe CentersAligning Tailstock

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To Align Centers by Adjusting the Tailstock1. Loosen tailstock clamp nut or level2. Loosen one of the adjusting screws,

depending on direction tailstock must be moved and tighten other until line on top aligns with line on bottom half

3. Tighten screw to lock both halves in place

4. Make sure tailstock lines still aligned5. Lock tailstock clamp nut or lever

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Alignment of Lathe CentersTrial-cut method

• Small cut taken from each end of work• Diameters measured with a micrometer

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To Align Centers by Trial-Cut Method1. Take a light cut (.005-.010 in.) to true

diameter from section at tailstock end about .250 in. long

2. Stop feed and note reading on graduated collar of crossfeed handle

3. Move cutting tool away from work with crossfeed handle

4. Bring cutting tool close to headstock end

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To Align Centers by Trial-Cut Method5. Return cutting tool to same graduated

collar setting as at first cut

6. Cut a .500-in (13 mm) length at headstock end and stop lathe

7. Measure both diameters with micrometer

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To Align Centers by Trial-Cut Method8. If both diameters not same size, adjust

tailstock either toward or away from cutting tool ½ difference of two readings

9. Take another light cut at both points at same crossfeed graduated collar setting

10.Measure diameters and repeat as necessary

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Alignment of Lathe CentersTest bar and dial indicator

• Fastest and most accurate method

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Alignment of Lathe CentersTest bar and dial indicator

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Aligning Centers Using Test Bar and Dial Indicator 1. Clean lathe and work center, mount

test bar2. Adjust test bar snugly between centers

and tighten tailstock spindle clamp3. Mount dial indicator on toolpost or

lathe carriage• Indicator plunger should be parallel to

lathe bed and contact point set on center

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4. Adjust cross-slide • Indicator registers approximately .025 in

at tailstock, indicator bezel to 0

5. Move carriage by hand so indicator registers on diameter at headstock end and note indicator reading

6. If both indicator readings not same, adjust tailstock with adjusting screws until indicator registers same at both ends

Aligning Centers Using Test Bar and Dial Indicator

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7. Tighten adjusting screw that was loosened

8. Tighten tailstock clamp nut

9. Adjust tailstock spindle until test bar snug between lathe centers

10.Recheck indicator readings at both ends and, if necessary, adjust tailstock

Aligning Centers Using Test Bar and Dial Indicator