Early Super 7

[Ray ReevesParticipant @rayreeves15364]

After much use I found that the rack and pinion was showing signs of wear. On further investigation there seems to be changes in the apron with bushing or maybe without it with different gears depending on the S7 year. Can anyone shine a light on this for me.

[Ray ReevesParticipant @rayreeves15364]

Apron Changes

[SillyOldDufferModerator @sillyoldduffer]

Welcome to the forum Ray. I expect someone will know the answer!

Photos often help with questions like this, so if if you have the technology please add some. With luck one of the Myford experts will recognise what you have. How to add images to the forum is described here.

Dave

[Bob McParticipant @bobmc91481]

Hi Ray,

I have recently finished a refurb on a Myford S7, this model was manufactured in 1964 and I believe is a mk2 version.

See forum posts 'Myford Super 7 for £395 at SRS'

I did extensive work on the saddle & apron, luckily the rack & pinon were in good order but after repairing the bed and saddle the fitting of the apron to the saddle was now lower than previously, and the right thickness shims had to be fitted at the interface of these two components to put the pinion in correct mesh with the rack.

I don't know what you mean by 'bushing' .. my interpretation is that a bush is a cylindrical collar but may mean something else to others. If both the rack & pinion are worn I can't see any way out of it but replacement of these parts however if the two are not in close contact it can feel as if they are worn and with some adustment of apron to saddle can be put back to a working situation, probably if worn there will be some backlash but I should imagine there would always have been an amount of backlash present even in the new item.

This was the apron prior to cleaning up the shim should ideally fit along the edge facing.

As Dave has mentioned a picture of the rack & pinion would give a better idea of the problem.

rgds..Bob.

[Neil LickfoldParticipant @neillickfold44316]

I would think that if any wear of the bed or the ways, it would require the opposite, and removal of material off the face shown to tighten the rack and pinion fit. Mine is a Mk2 of 1972, not 1974 as I thought, but has the saddle across the bed , not the narrow type. The pinion shaft cover on the other side has a brass or bronze bush in the cover by the pinion gear itself. There is no adjustment for this height. The pinion on my lathe does have some wear, and at some stage the rack and pinion for the lathe should be replaced. There maybe some adjustment of the rack itself but I have not removed it to see. The backlash in the handwheel does not bother me, but it does not have very much anyway. There will always be some backlash and there is a reduction gear between the hand wheel and the pinion as well. It is possible that the early covers did not have a bush or sleeve in them. The casting has a hole to limit the max total amount of oil in the reduction box . Keeping the rack clean is a task often over looked as it is upside down and does seem natural to think it can't get dirty.

My apron has no shims between it and the saddle.

When putting it back together, I used the 1/2 nut to align it all with and then put in the screws, looking at the leadscrew to ensure that it was not being influenced with the 1/2 nuts fully engaged. I then sight through the end of the bed along the rack, to see if the pinion is near fully engaged. Which it is. Recently added a front DRO and I indicated the apron after how I described above and it was within 0.03mm over the 80mm length indicated. Close enough for the reader head and close enough that it did not need adjusting. 

 

Edited By Neil Lickfold on 01/06/2022 20:20:11

[Phil super7Participant @philsuper7]

I agree with Neil, there no shims to adjust the height of the saddle, the only shims used are for the saddle strip.

One of restrictions on regrinding the bed is the rack. Myford use to say 10 thou, as this is the amount of movement the rack can be moved up to re engage with the pinion. Remember regrinding the bed involves repositioning both rack & Leadscrew.

PS I had all these questions rebuilding a S7 many years ago but was fortunate to live not to far away from Myford so use to go to buy parts then go into the workshop and ask the fitters "how do you do this then", they were always very accommodating.

I can also recall asking how old is my lathe, and this gentlemen went of upstairs in the fitters shop came back with a notebook with every machine serial no date and who originally bought it recorded. I wish i knew where that book is now

[Martin KyteParticipant @martinkyte99762]

Not as good as the individual list of who bought what and when but the dating of Myfords can be done by the list of Serial No's here:-

**LINK**

regards Martin

[Peter SansomParticipant @petersansom44767]

A bit of play on the gear on the rack is not a real issue. Normally on a S7 you use the lead screw hand wheel while cutting.

I have a 1958, Mk1 head stock, MK2 clutch and yes there is some play in the rack feed, not an issue. Sometimes I will use teh carriage hand wheel to advance the carriage when machining. The play does not matter as you are moving the carriage by gentle pressure.

I will improve rack feed slack at some point but it does not impact performance.

Of more importance was

1 fix bed wear – bed grind

2. replaced clutch bearings and headstock bearing, did tapper roller bearing conversion

3. adjusting the lather to turn parallel

Peter

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