Myford S7 Power Cross Feed Apron Adjustments

[Mike DonnerstagParticipant @mikedonnerstag]

I have a Super 7 with power cross feed saddle. When I received the lathe, the half nut lever was stiff. I slackened the gib screws to ensure the gib moves freely, though the half nut lever only eases off when I loosen the two large screws at the front (LA8 in the manual). Can anyone tell me whether these should be tight and whether I am perhaps tightening things in the wrong order? I have had the saddle off in the past and everything is clean and oiled.

I also wondered what the socket grub screw in the side does (LA58) and whether this should be tight.

The only adjustment given in the manual is for the 2BA cap screw (LA6). I have to admit that I am similarly confused about how this is adjusted. The manual states, "…adjust the setting … until it is in contact with the under side of the upper half of the leadscrew nut". How do I determine this when it can't be seen?

Any information gratefully received.

Mike

[Mike DonnerstagParticipant @mikedonnerstag]

[John PurdyParticipant @johnpurdy78347]

Mike

The two screws (LA8) lock the gib to the apron casting and have to be slacked off to allow adjustment of the gib, once adjusted they are tightened up to lock the gib in position.

I have had the carriage off my lathe many times and the way I adjust it is before putting the apron back on I slack off the two screws LA8 and adjust the gib so that the half nuts move easily with no play when opened and closed with the lever, tighten the screws LA8, hold the apron up to the saddle and put in the 4 screws (LA49) in the  the saddle to hold the apron on but don`t do them up, leave them loose so the apron can still be move a bit ( the holes in the saddle are over size to allow this) , re-install the lead screw, position the carriage as far to the right as possible, then engage the half nuts and with them engaged solidly on the lead screw tighten up the 4 screws holding the apron to the saddle. This ensures that when the half nuts are engaged with the lead screw the lead screw is not bent out of alignment. As far as the adjustment of LA6, what I do is with the half nuts closed on the lead screw just to screw it in till it just stops by feel. That`s always seemed to work.

Just a note, by far the easiest way to remove the apron and saddle is to first remove the lead screw by removing the two screws and two dowels in the bracket at the right hand end of the lead screw and withdrawing it totally out of the apron to the right.

John

Edited By John Purdy on 27/03/2019 17:36:19

[Mike DonnerstagParticipant @mikedonnerstag]

Just a quick update on this problem I posted last year. I removed the apron assembly (to replace several bushes) and found that the gib strip (LA7) was tight against the bevel of the half-nuts and the apron casting regardless of the position of the gib adjusting screws. I cleaned everything and checked that there was no burring to the gib strip, to no avail.

I remedied this by fitting a shim (cut from an old aluminium venetian blind, around 10thou thick) between the gib and the apron. The gib can now be tightened with the pan-head screws (LA8) and adjusted with the gib adjusting screws (LA9 and LA10).

Perhaps this was due to the half-nuts having been replaced in the past with remanufactured and slightly oversized items??

Mike

[KWILParticipant @kwil]

LA58 should be tight. It holds the clasp nut cylinder in place, but the shaft is itself eccentric to allow the centering of the clasp nut on the leadscrew.

When engaging the clasp nut the leadscrew should NOT move in the vertical plane. If the leadscrew moves in the horizontal plane, the apron securing bolts are wrongly placed.

[Mike DonnerstagParticipant @mikedonnerstag]

Many thanks KWIL. I've tightened the LA58 after adjusting the 'cam' LA55 to ensure the leadscrew doesn't move when the half-nuts are engaged.

Mike

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