Myford S7 Taistock Adjustment

[Harry WilkesParticipant @harrywilkes58467]

I find myself needing to adjust the tailstock on my Myford super 7, I have never tried to adjusted up to now and cannot seem to find any instructions. I have seen the to adjusting screws at the front end and the one on the righthand side at the rear but I thought I would ask for advice/instructions before I had a play and messed something up so if anyone can help I would appreciate it.

H

[Andrew TinsleyParticipant @andrewtinsley63637]

The adjusting screws are self explanatory, they just move the tailstock sideways. The trick is when do you have it correctly on the axis of the lathe?

I put a centre in the headstock and in the tailstock. I then bring the two together with an old razor blade or piece of shim trapped between the two, when the shim is at right angles to the lathe axis then the tailstock position is correct.

May sound a bit crude, but it works for me. I am sure there are super accurate ways of doing the alignment, but others can tell us what they are.

Andrew

[Howard LewisParticipant @howardlewis46836]

Presumably, you have an alignment bar so that you can align between centres.

Having set the bar between centres, the clock needs to be on centre height, and traversing between Headstock and tailstock will tell you how far out, if at all, the tailstock is.

If it is out, you should find a grubscrew low down on the front and back sides of the tailstock, with which the upper part of the tailstock can be adjusted across the bed (and the firmly clamped tailstock foot).

By adjusting these, you should be able to reduce the clock reading, so that it reads the same at both ends of the alignment bar.

BUT, if your concern is that the lathe is cutting a taper, have you checked, for twist in the bed?

No lathe will cut parallel if the bed is twisted.

If the bed is twisted, it will cut a taper, so check first. The 7 Series bed is not particularly strong in torsion, so does need to be checked and levelled correctly.

The method advocated by Myford is outlined in Ian Bradley’s “The Amateur’s Workshop” and “The Myford 7 Series Manual” ( Otherwise known as “Rollie’s Dad’s Method”)

This involves making a “cotton reel”, about 6″ long,using very fine cuts, and measuring the OD at each end.  The books will then tell you which side of the feet at the tailstock end, to shim or adjust, to eliminate the twist

The torque applied to the securing bolts / nuts can have quite an effect!

Once any twist has been eliminated, then Tailstock alignment can be checked.

HTH

Howard

 

[SteviegtrParticipant @steviegtr]

I 2nd Andrews comment.

Steve

[John PurdyParticipant @johnpurdy78347]

Harry

There are two slotted grub screws, front and back, just below the bed locking lever. To adjust the tail stock slack them both off and just nip up the tailstock to the bed. Then tightening the front screw moves the tailstock toward the front, tightening the rear one moves it toward the back. To move it one way or the other the opposite screw must be slacked off. Once set where you want it, tighten both. Note, they are very stiff to move, at least on my lathe.

John

[John HaineParticipant @johnhaine32865]

Provided your centres are accurate, Andrew’s method is probably the most precise, as the angle the blade takes up is a function of the misalignment and the blade’s thickness.  It’s something like the inverse tan of the ratio of misalignment to thickness, so a small misalignment gives a very obvious angle.

[John PurdyParticipant @johnpurdy78347]

Harry

To add to my last, the reason I say to “just nip up the tailstock to the bed” is to just stop it from moving while making the adjustments. If you lock it solidly to the bed it is then extremely difficult if not impossible to adjust the tailstock with the grub screws. This is because as can be seen in the diagram below the action of locking the tailstock to the bed not only does that but in the process applies the locking force between the two halves of the tailstock  body.

John

[duncan webster 1Participant @duncanwebster1]

I’ve not read all of this thread, so someone might already have mentioned this. With early Myfords, as the inner edge of the shear closest to the user wears the tailstock is less well guided. You can’t take all the slack out or the tailstock won’t go to the right hand end. Therefore it is as well to always push the tailstock away from thd operator by hand before locking it if you’re after the last thou.

[howardbParticipant @howardb]

My method on my S7B some time ago, to ensure that the centre line of the tailstock barrel is aligned with the centre line of the headstock spindle is:-

Make sure that the bed and the bottom of the tailstock are both clean, I  removed,stripped and cleaned the tailstock before doing this as I bought the lathe from a clockie and it was infested with brass swarf, I’m still finding brass swarf today !!

Hold or mount a dti in a chuck or collet in the spindle so as to have the indicator arm contact the OD of the tailstock barrel, with the barrel locked and the tailstock locked to the bed. Zero the dti.

Turn the spindle and watch the indicator reading – use an inspection mirror when/if it goes out of vision. Adjust the alignment screws to achieve the least movement of the dial when the dti reads the front as the back of the OD of the barrel.

When it reads top and bottom – the difference is the amount of bed wear is present if any.

 

[SteviegtrParticipant @steviegtr]

Don’t forget to wind out the tailstock to about 3/4 before testing the centres with centre points. It is not hard to find the centre points. Once found then snug up the adjustment screws & all should be good for the future. .

Steve.

[Martin KyteParticipant @martinkyte99762]

Couple of thoughts.

Ensure your lathe turns parallel before adjusting the Tailstock.

For precision turning between centres set the work so the tailstock is at the correct point on the bed and lock it. Note the quill extension and remove the  work. Centre the tailstock using a dial gauge in the headstock with the quill extension as noted. Use the smallest quill extension you can.

[Harry WilkesParticipant @harrywilkes58467]

Thanks to everyone job done, and i’m more than happy with it.

H

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