Mounting, Removing, and Aligning Lathe Centers Unit 49

Objectives Mount and/or remove lathe centers properly Align lathe centers by visual, trial-cut, and dial-indicator methods

Lathe Centers Work machined between centers turned for some portion of length, then reversed, and other end finished Critical when machining work between centers that live center be absolutely true Concentric work

To Mount 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

To Remove 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

Alignment of Lathe Centers Parallel diameter produced when lathe center aligned Three common methods used to align Aligning centerlines on back of tailstock with each other Only a visual check and not too accurate Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Alignment of Lathe Centers Using the trial-cut method where small cut taken from each end of work and diameters measured with a micrometer Using parallel test bar and dial indicator Fastest and most accurate method Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

To Align Centers by Adjusting the Tailstock Loosen tailstock clamp nut or level Loosen on of the adjusting screws, depending on direction tailstock must be moved and tighten other until line on top aligns with line on bottom half Tighten screw to lock both halves in place Make sure tailstock lines still aligned Lock tailstock clamp nut or lever

To Align Centers by Trial-Cut Method Take a light cut (~.005 in.) to true diameter from section A at tailstock end for .250 in. long Stop feed and note reading on graduated collar of crossfeed handle Move cutting tool away from work with crossfeed handle Bring cutting tool close to headstock end

To Align Centers by Trial-Cut Method Return cutting tool to same graduated collar setting as at section A Cut a .500-in (13 mm) length at section B and stop lathe Measure both diameters with micrometer

To Align Centers by Trial-Cut Method If both diameters not same size, adjust tailstock either toward or away from cutting tool ½ difference of two readings Take another light cut at A and B at same crossfeed graduated collar setting. Measure diameters and adjust tailstock.

To Align Centers Using Dial Indicator and Test Bar Clean lathe and work center, mount test bar Adjust test bar snugly between centers and tighten tailstock spindle clamp Mount dial indicator on toolpost or lathe carriage Indicator plunger should be parallel to lathe bed and contact point set on center

To Align Centers Using Dial Indicator and Test Bar Adjust cross-slide Indicator registers approximately .025 in at tailstock, indicator bezel to 0 Move carriage by hand so indicator registers on diameter at headstock end and not indicator reading If both indicator readings not same, adjust tailstock with adjusting screws until indicator registers same at both ends

To Align Centers Using Dial Indicator and Test Bar Tighten adjusting screw that was loosened Tighten tailstock clamp nut Adjust tailstock spindle until test bar snug between lathe centers Recheck indicator readings at both ends and adjust tailstock, if necessary