Myford Super 7 Belt Changes: Step-by-Step Service Manual PDF (EN)

SERVICE MLL . Perhaps one of the most avoided service chores on your Super 7 or ML7-R lathe is the task of replacing the secondary/headstock drive belt. Naturally we understand your reluctance to tinker with the headstock, after all logic tells us "don't disturb the spindle - it may not perforrn as well again ifwe take it ipart". However, having had the opportunity to appraise your workmanship over the years, we think that your reluctance is ill-founded, and that this task is well within your capabilities. Below we have endeavoured to give a step-by-step guide which we hope will simpliff the procedure.

Please note these instructions apply in particular to the current Super 7 lathes fitted with the cone clutch and ML7-R lathes fitted with the additional 30/040 countershaft clutch unit. The instructions with regard to removing the count€rshaft will, therefore, not apply to standard ML7-R lathes and pre-1958 Super 7 lathes which will be fitt€d with an expanding mandrel clutch unit. Many problems have occurred in the past as a result ofyour misconception ofthe headstock spindle bearing arrangement. Your task will be very much simplified ifyou visualise the headstock anangement as two units:

The spindle, complete with angular bearings locked in place as one unit, and the headstock fitted front bush and castillated adjusting collars as the other Axial movement (end float) is controlled by a pair of angular contact bearings, mounted back to back (the face of an angular contact bearing is the open end). These bearings are designed to carry the heavy end loads applied by such operations as drilling. For angular contact bearings to work effectively they have to be pre- loaded - this is achieved by a shim being inserted between the outer races of the bearings. The inner races abut to a shoulder on the spindle 21 through a spacer and is adjustcd via the gear 37 and the collar 33.

Radial Clearance - the final adjustment to ensure maximum spindle precision and rigidity is achieved by sliding the whole spindle unit (complete with angular contact bearings) in or out of the tapered front bush. This movement is controlled by the two adjusting collars T4A and 748, and it is important to ensure that the two collars are always finally locked together which ensures that the preJoadihg shim is fully effective. the principle ofthe tapered bronze bearing is that it needs to be set in such a way to give just sufficient clearance for a fi.lm of oil to support the spindle whilst running. Fine tuning may be carried out by adjusting the locking collars by small increments.

Requirenents:- You will need to provide the following equipment to carry out the belt changing. I trs" & sr32" A.F. Allen keys . 1/4" BSF spanner 'C'Spanner o Scriber ',: 12" steel rule No. 1 Hide,/Copper mallet & Whitc spirit or turpe eubstitute " Paint brush Newspapers It is irnportant to use white spirit or turps substitute for cleaning purtr oses. You must not use paraffin as it encourages rusting and on no account use thinners as they will adversely affect the paintwork of the lathe. Circlip pliers (Part No. 78008) i'l,liXtlJSi*..0"n A29 .Sl right and remove the woodruffkey 103.

8 Supporting the cone pulley 106 in your right hand, take hold of the twin Vee pul- ley 112 with your left hand and gradu- ally start to ease the whole countershaft assembly out of the swins head r.- rzo. ihe "orr.r- [P tershaft need only be withdrawn enough to remove the cone pulley. Try to keep the clip on the shaft. 9 Invariably the push bar 117 and grre" dia. steel ball 123 will have been left behind in the right hand bearing housing of the swing head bracket 120. By removing the end cap 119 with a screw driver, these items can be recovered and refitted into the end of the countershaft 102, with the ball facing outwards. Replace the end cap.

10 Carefully clean and dry all the parts and wash down the inside of the housing, using newspaper to collect ihe excess spir- it. Dry down thoroughly. 11 Fit the new V belt (70001) to the puiley. Ensure that the pulley is the right way round. 12 Line up the cone pulley with the coun- tershaft. 13 Take hold of the twin Vee pulley and feed the countershaft back into the cone pulley until the woodruff key slot is just to the right ofthe circlip. t4 With the woodruff key slot fully exposed, refit the woodruff key, line up with the keyway in the cone pulley and slide the pulley over the key. 15 Using the cone pulley, push the circlip back into its groove.

16 With a 12" steel rule, line the coun- tershaft cone pulley up with the cone pulley on the 66 spindle arad v secure by locking the lra" BSF socket set screw 19. 77 Check the adjustment of the clutch - there 6 needs to be t/ about 1/4" free play at the ball handle when the clutch is in the engaged position 40. Adjustment is carried out by releasing the la" BSF hexagon lock nut 29 and by screwing the push rod 115'in" or "out'as required. Relock the hexagon lock nut. 1 Cut the old headstock V belt and dis- card. 2 Remove the primary belt drive. 3 Move the clutch operating lever to the engaged position 40. There must be some free play (see 17).

4 Release the lre" BSF socket set screw 19 in the cone pulley 106. 5 Slide the cone pulley to the right. 6 Using a pair of right angle external circlip pliers (part No. 78008) remove the circlip l0l from its groove and slide l'n"ii"li,'lT P 106. cir- almost touches the woodruffkey 103. 7 With the key facing upwards, start to withdraw the countershaft 102 to the Ieft until the circlip 101 almost touches the col- lar 100. Slide the cone pulley 106 to the UALIru...TOBE PRECISE/

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32 The cone pulley assembly 2 and the 60T backgear assembly 80 with the woodruffkey slot at the top, should be fit- ted into place between the front and rear bearings of the headstock. 33 Feed the spindle back into the head- stock, remembering to make sure that the woodruff keyways face upwards(2Z3 V :r,r#jtace woodruff keY 22A in the 44 If, by mistake, you overtighten the bearing adjusting ring 74B causing the spindle to lock - slacken the adjusting ring 748 by half a turn and using a hide mallet tap the spindle 21 towards the tailstock (left to right). Return to 43. 45 T\rrn the outside bearing adjusting ring 744 approximately one turn anti- clockwise until it locks.

Give the 'C' spanner a sharp wrap with the mallet. 46 By sliding the 60T backgear assembly 80 in the appropriate direction, set the cone pulley 2 with approximately 0.005" end float. Lock the backgear 80 with the t4" BSF socket set screw 8. 47 Remove the scriber pinning the lubri- cation wick and replace the 2BA socket set screw 26. 48 Check the alignment of the two cone pulleys and re-adjust the countershaft pulley if necessary. 49 Place the belt onto the countershaft pulley. 50 Adjust the belt tension by releasing the two 1/4" BSF hexagon nuts 29 and turning the two adjusting il:"niJ,;l ate direction. 18 Release the 2BA cap head screw 34 in the adjusting collar 33.

19 Unscrew and remove the adjusting collar 33. 20 Remove the 30T gear 37 from the spindle 21. 21 Remove the woodruff key 224 from the spindle 21. 22 Release the lra" BSF socket set screw 8 in the 60T backgear assem- bly 80. 23 Position the spindle so that the key- ways 22A and 228 face upwards. Tbis iq verv imoortant as it is imoossi 36 Refit adjusting collar 33 Ito the lspindle. 37 Engagebackgear. 38 Using the allen key for the 2BA head screw 34, as a lever, tighten thp adjusting collar 33 as tight as possible. {i I ! I, 39 Disengage backgear. 40 Lock up the 2BA cap head screw 34 to secure the adjusting collar 33.

41 Using the'C'spanner, turn the outside bearing adjusting fing 744, two turns clockwise (when viewed from the spindle nose). 42 T\rrn the inside bearing adjusting ring 74B approxi- mately 330 deg. (7 slots ) clockwise. 43 Make sure h- there is no ten- F sion on the V belt, place the middle finger of the right hand on the 607 backgear and rotate the spindle. Whilst ff*Y#,Ti"l: F tinue to turn the inside bearing adjusting ring 748 clockwise until you start to feel 30T gear 37 to the spindle. spindle is in-situ. With the keyways fac- ing upwards, woodruff key 228 will clear the front bush as the spindle is with- drawn from the headstock. 24 Using a no.

t hide mallet drive the spindle out of the headstock from left to right. 25 Remove the cone pulley 2 and back- gear assembly 80 from the headstock. 26 Carefully clean and dry all the compo- nents you have removed with either white spirit or turps. substitute. Also clean inside the headstock area and dry thor- oughly. 27 Remove the 2BA socket set screw 26 from underneath the front of the bronze spindle bearing 62. 28 Using a suit- able tool, depress the lubrication wick so that it is well below the Hff'T',T; F front spindle bear- ing. Secure the wick in position by pinning with a scriber through the tappedhole26.

l 29 Using a'C'P spanner, turn the inside bearing adjusting ring 74B, one turn anti clockwise (when viewed from the spindle nose). 30 T\rrn the outside bearing adjusting ring 7tlA, one turn anti-clockwise (when viewed from the spinille nose). 31 At this point it will be easier if the V belt is moved to the extreme right of the countershaft (the belt should rest on the shaft itself and not the cone pulley). Fit the cone pulley assembly 2 onto the new V belt, ensuring that the cone pulley is the right way round. 51 Replace the primary drive belt and if necessary re-adjust for tension. the spindle drag in the front bush. ' \ M'Pa€aA l.7 t : l^L SfrP +3 .

A f U_LV,*flld-d W:, T.] ALITY., .T O BE PRECISE I

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Headstock Bearing Adjustment Myford Super 7 ) 1. Slacken Split Collar, nut'A' and nut'B' 2. Holding the bull wheel, tighten the Split Collar fully bv hand and tighten the clamping screw. There should be a scribed line on the mandrel which, when new, lined up with the split in the collar. Some drift (5, 10 deg?) due to wear is acceptable, but if it is way ou! something is amiss. 3. Tighten nut'B' cautiously with a'c' spanner until mandrel can still be turned by hand without great effo$ but action has become stiffandjerky.

)r Tighten nut'A'fully, giving the spanner a clout with a soft- faced hammer (yes, really) Mandrel should now turn smoothly by hand (via the bull wheel), but still be noticeably (surprisingly) stiff. %

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