Myford ML7 Lead-screw – Woodruff Key Slot Spacing?

[Swarf, Mostly!Participant @swarfmostly]

Hi there, all,

I am seeking to 'modernise' an early Myford ML7 lead-screw (see below for explanation of 'modernise' ).

Please could anyone who has a modern ML7 lead-screw (not currently fitted to an ML7 ) measure the distance between the two Woodruff key slots at the head-stock end of the screw and either post here or PM me with their result? Please specify whether your measurement is centre-to-centre, overall or inner end to inner end, better still please include a sketch or annotated photo.

Explanation: early ML7 lathes, i.e. prior to the introduction of the quick-change gear-box, had/have a single Woodruff key slot at the position of the lead-screw gear that accepts the drive from the 'up-stream' change-wheels. Lathes fitted with the QC gear-box have a shorter lead-screw with a Woodruff key slot positioned to suit the gear which accepts the output from the gear-box. At some suitable stage, Myford rationalised production of the lead-screws by putting in two Woodruff key slots, one in each position. In a non QC gear-box lathe, the right-hand slot 'hides' in the left-hand lead-screw support bearing.

I have an 'early' lead-screw which has only the single slot and which I am hoping to modify to the later standard.

Hoping someone will be able to answer this request,

Best regards,

Swarf, Mostly!

[Swarf, Mostly!Participant @swarfmostly]

[Brian WoodParticipant @brianwood45127]

John Stephenson would 'modernise; it by cutting a slot along the shaft to fit square keys instead, is that an option you can adopt here. He really doesn't like woodruff versions.

Regards

Brian

[TSHParticipant @tsh73987]

As it happens my ML7R is in pieces while the bed is away being re-ground. The leadscrew is as you describe and the distance between corresponding parts of the slots is 39.8 mm. (i.e. left side to left side, or right side to right side) .

However, the ML7R reportedly has the headstock and other parts (but not the cross-slide) of the Super 7, so maybe this measurement will be different on the ML7.

Regards,

Trevor

[Swarf, Mostly!Participant @swarfmostly]

Hi there, Brian,

Thank you for your post.

I am aware of and respect John's opinion regarding square vs Woodruff keys. I'd guess that the load on the ML7 lead-screw is very much less than on some of the machinery John deals with. When fitting the QC gear-box, one moves the key from the LH slot to the RH slot after shortening the screw, so the Woodruff key is in-hand, whereas a square key might not be. However, I do have end-mills whereas I don't have a Woodruff key cutter so your steer is welcome.

Still, my major concern is exactly where to put the key slot, even if I machine for a square key, I'd want the slot to be closed-ended, at least until the lead-screw needs to be cut to the QC gear-box length. So my original question stands.

Best regards,

Swarf, Mostly!

[Swarf, Mostly!Participant @swarfmostly]

Posted by TSH on 27/09/2016 16:26:43:

As it happens my ML7R is in pieces while the bed is away being re-ground. The leadscrew is as you describe and the distance between corresponding parts of the slots is 39.8 mm. (i.e. left side to left side, or right side to right side) .

However, the ML7R reportedly has the headstock and other parts (but not the cross-slide) of the Super 7, so maybe this measurement will be different on the ML7.

Regards,

Trevor

Hi there, Trevor,

Thank you for your post.

My gear-box originally came from a Super 7 which has a ¾" diameter lead-screw rather than the 5/8" of the ML7. Apart from the lead-screw diameter, the only other major difference, ML7 vs Super 7, that I know about is that the change-wheel covers are different (though the back-plates are the same). I should mention that some Super 7 QC gear-box installations required a shim behind the gear-box. This might have only applied to early machines – does anyone out there know?

The fact that the gear-box and change-wheel back-plate are identical suggests that the ML7 and Super 7 are identical in the axial direction.

Some lead-screws, I assume the later ones, are made in two pieces with a coupling sleeve and roll-pins (I don't think either pin is a shear-pin) with the section that goes through the gear-box of 5/8" diameter for both ML7 & Super 7 versions. If the lead-screw protector is shortened according to the Beeston installation instructions, it fouls the coupling when the saddle is still some way short of the end of the bed – I took a further inch off mine!

Best regards,

Swarf, Mostly!

[not done it yetParticipant @notdoneityet]

John Stephenson would 'modernise; it by cutting a slot along the shaft to fit square keys

JS is spot on. Woodruff keys are a pain. Square tool steel is cheap and easily cut to length. End stops, for the key, can be incorporated for most applications. Even making the key rectangular from bar is not difficult, should the width of the key be a problem in square format.

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