Singer Centurion 121C Service Manual Download Page 1

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Summary of Contents for Centurion 121C

Page 2: ...wing Machine Supply LLC www supsew com Form 21624 Rev 977 I UAL I Sewing l llachine 121D CLASS 121C CLASS Copyright 1976 The Singer Company All Rights Reserved Throughout the World A Trademark of THE...

Page 3: ...ted bushings which require no manual lubrication The following exceptions are HOOK An oil reservoir supplies oil to the sewing hook race and is filled through the oil cup as shown with Singer Type C o...

Page 4: ...per and compare oil pattern with Fig B for proper oil flow I FIG B If there is no trace of oil or an excess adjustment should be made with the oil metering screw In order to gain access to oil meterin...

Page 5: ...oil filter Check filter Oil wick should be replaced whenever it has become clogged with lint or dirt An excess of oil sometimes indicates that the filter wick has become detached from the screw or th...

Page 6: ...gh 3 eyelets of thread guard 4 Units with U T T through pretensioner 5 Down through thread retainer 6 Into and around tension assembly 7 Over check spring and under slack thread regulator 8 Up to and...

Page 7: ...mb Screw More Less FIG A Stitch Length 01 t Regulating Screw IRB i tit J I FIG B FIG C PREVENTING UNAUTHORIZED CHANGES IN STITCH LENGTH To prevent unauthorized changes in stitch length remove the reta...

Page 8: ...ne The one atop the arm is the major control normally adjusted prior to long production runs or new applications For day by day casual adjustments the regulating screw al the rear is used screwing in...

Page 9: ...t ween the two Fig A To adjust clearance loosen bushing set screw Fig B With screwdriver placed as shown move entire hook and bushing Fig C Tighten bushing set screw Hook Bushing Set Screw FIG B Insur...

Page 10: ...bar is on the rise stroke and the lowest mark is aligned with the needle bar height indicator Set hook point to the centerline of the needle Fig F Tighten hook set screws FIG F Hook Point to Centerli...

Page 11: ...d shaft timing belt pulley set screws Fig B Hold pulley stationary and rotate bed shaft until timing line at feed bar end of shaft aligns wiih timing mark on casting Fig C Timing marks alignment in Fi...

Page 12: ...TING Loosen feed bar carrier pinch screw Fig 8 Shift feed bar as re quired to locate feed dog in throat plate slots as shown above Ensure that feed bar does not contact position finger not shown Tight...

Page 13: ...centric feed bar hinge pin Visually adjust to bring feed dog at maximum height above throat plate and tighten both hinge pin locking screws This will locate the slot shown in a vertical position Fig...

Page 14: ...cally 4 Tighten screws A and B 5 Loosen nut D Fig 1 6 Turn eccentric stud E several times Please note that the feed bar will rock back and forth Visually position feed bar rock motion towards the oper...

Page 15: ...From the library of Superior Sewing Machine Supply LLC www supsew com I Slot in Vertical Position A Slot in Vertical Position FIG 1 FIG 2 13 043 Inch for All Other Types of Material...

Page 16: ...he check spring should return to its original position To adjust height loosen locking set screw Rotate entire tension assembly as required and retighten set screw FIG A TENSION Tension Assembly Locki...

Page 17: ...n sooner and towards rear of machine to open later After desired adjustment retighten alien screw wcap I Block 0 0 FIG A PRESSER BAR AND FOOT SETTING With feed dog positioned below the throat plate su...

Page 18: ...GHT using timing marks 200 VARIETY MACHINES Turn machine pulley slowly until needle bar is at its lowest point Loosen needle bar clamping screw shown in Fig C and raise or lower needle bar UNTIL THE C...

Page 19: ...left toward the sewing head end of the machine as far as the holding screw slots will allow Tighten holding screws 4 Move drive wheel on arm shaft until it touches driven whdel Tighten set screws BOB...

Page 20: ...ghten set screw 2 Loosen set screw in collar of thread guide Move guide in or out to obtain even wind on bobbin Retighten set screw 3 Adjust tension as required in clockwise for more and out countercl...

Page 21: ...spring washer and rod com plete 9 10 Unscrew and remove pressure lever mounting screw and lever complete 11 Unscrew and remove presser bar pressure lever adjusting screw 12 13 Remove lower spring and...

Page 22: ...BAR FRAME AND TAKE UP MECHANISM 1 Remove 5 rear arm cover mounting screws 2 Remove rear arm cover and gasket 3 Loosen needle holding screw and remove needle 4 Remove oil wick from take up hinge stud...

Page 23: ...d guide 7 Loosen take up hinge stud mounting set screws 8 Loosen needle bar crank set screw and clamping screw 9 Loosen needle bar frame mounting screw upper 10 Loosen needle bar frame mounting screw...

Page 24: ...nd lifting lever mounting screw and lever 5 Remove tension releasing pin ARM SHAFT 1 Loosen set screws 2 ea in each of the components named in the illustration below The handwheel should then be remov...

Page 25: ...d bar from height eccentric stud This will give access to feed lifting link screw 5 Loosen set screws 2 each in the following components drive pulley timing belt pulley feed eccentric collar and gear...

Page 26: ...om DISASSEMBLY SEQUENCE FEED ROCK SHAFT 1 Loosen set screws 2 ea in collars 2 Loosen clamping screw in feed reversing crank 3 Loosen clamping screw in feed bar carrier 4 Remove shaft from right to lef...

Page 27: ...vertical link 2 Loosen set screws in drive assembly 3 Loosen set screws in collar 2 ea 4 Loosen set screws in dynamic damper 2 ea 5 Slip short shaft from left to right and long shaft from right to lef...

Page 28: ...nd cover plate and twist 2 Remove stitch indicator cover plate unit and light box 3 Loosen reversing lever shaft set screw in arm casting 4 Loosen set screws in collars 2 each 5 Slip shaft out from ri...

Page 29: ...Loosen sleeve set screw from bed casting 8 Remove E ring and link from bell crank unscrew link from pivot pin and remove with oil seal 9 Loosen set screws in stop arm collar and crank 10 Remove shaft...

Page 30: ...er pan cover and bed cover pan 3 Remove feed rock shaft as per prior instructions 4 Move feed bar to allow clearance for bushing removal 5 Drain oil and remove oil reservoir cover 6 Remove oil line fi...

Page 31: ...n 3 Assemble stitch indicator cover plate light box reverse lever stopping block and the stitch indicator cover plate unit 4 Centralize shaft in arm standard axially with left collar up against castin...

Page 32: ...ten set screws in drive assembly 5 Tighten set screws of dynamic damper onto flats of shaft 6 Move entire assembly to left until touchi11g casting Move collar to right until touching casting Eliminati...

Page 33: ...reversing crank and collar Set shaft flush with left bearing face Move left collar to left until touching bear ing face Tighten set screws Move right collar to right eliminating end play max 001 Tigh...

Page 34: ...washer collar gear oil pump and into feed bar lifting crank Replace screw 2 Rotate shaft to expose flats 3 Replace flange and drive pulley Tighten first set screw in direction of machine rota tion ont...

Page 35: ...A inside bushing until shaft position groove aligns with bearing face C Tighten collar A set screws 2 Replace gear eliminate end play and tighten set screws onto flats 3 Replace complete assembly into...

Page 36: ...y to bed casting with two screws Connect both horizontal and vertical links to bell crank assembly with to E rings 6 Mount knee lifter stop arm spring and drum assembly to bed casting with threaded st...

Page 37: ...ghtly tap arm shaft from left to right until front arm shaft bear ing is properly seated in casting Tighten set screws in intermediate bearing Rotate shaft to expose flats and position counterweight w...

Page 38: ...E MECHANISM 1 Insert tension releasing pin 2 Replace hand lifting lever and mounting screw 3 Replace tension releasing lever with spring in place 4 Insert mounting screw and tighten 5 Replace presser...

Page 39: ...dead center into the throat plate needle hole Lock studs No 1 and 2 in place with set screws provided 4 Insert thread take up hinge stud with flats facing upward through take up mechan ism into arm c...

Page 40: ...er foot with screw shown 3 Slide delrin spacer over presser bar 4 Mount guide bracket and screw see page 15 for setting 5 Mount spring and guide 6 Assemble presser bar pressure lever adjust ing screw...

Page 41: ...ng Machine Supply LLC www supsew com SERVICE INSTRUCTIONS FOR COMPOUND FEED SYSTEM 121C CLASS Servicing instructions for 1 21 D Class machines also apply to the 1 21 C Class with the exception of the...

Page 42: ...3 Set stitch length to zero stitches per inch in forward feed direction as shown on page 5 4 Position connecting rod slide block stud perpendicular 90 to machined surface of arm casting Fig 1 and tig...

Page 43: ...te Compound Feed Feed Dog Compound Feed FIG 3 8 Set feed dog as shown on pages 10 and 11 with one exception Lengthwise Set ting In this case set machine at zero stitches per inch and position feed dog...

Page 44: ...emove tension assembly with releas ing pin 6 Remove thread take up lever guard and thread guide complete Remove pretensioner if assembled 7 Remove face plate assembly and presser bar system as shown o...

Page 45: ...ch screws in connecting rod clamp upper and remove wicking 16 Loosen set screws in collar 17 Remove crank shaft assembly collar and connecting rod clamp upper 18 Untie knot on wicking end and remove f...

Page 46: ...From the library of Superior Sewing Machine Supply LLC www supsew com ASSEMBLY SEQUENCE 12 I 7 10 44...

Page 47: ...cking and place into pinched clamp as illustrated 10 Install needle bar frame and thread take up mechanism as shown on page 37 with two additions First mount and fasten conventional throat plate with...

Page 48: ...that step 5 has been incorporated 20 Assemble rear arm back cover and gasket All are not illustrated 21 Assemble bed cover gasket sucker wick holder sucker wick and stitch regulating knob complete Ple...

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Singer Centurion 121C, Service Manual

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Summary of Contents for Centurion 121C

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