The first photo in your set shows the first driver set of the leadscrew chain. The following comments assume a lathe doesn't have a gearbox fitted.

Following typing the rest of this diatribe I've re-visited your photos and realised that you must have a gearbox fitted as you've got a copy of its manual.

The gear which is fixed to the bronze bush engages with the tumbler gears for forward/reverse drive of the leadscrew.

Onto this you fit the first drive gear to start the screwcutting/fine feed change gears in motion (Most commonly a 20 tooth gear for imperial, or 21 tooth for metric threads, on a non-gearbox lathe).

You should have one on your lathe now assuming the leadscrew/gearbox turns when you operate the lathe.

N.B. If you have a fixed ratio dual sized gear in place at the moment, it's most likely the one designed for an even finer feed of the leadscrew, which will give you all the wrong pitches if you try screwcutting. (this is available as an optional extra)

The bolt with a flat section below the head, is to set up another pair of gears in the drive chain, not for the gear with the attached keyed stub. The squared off bit saves it rotation on the banjo. There should also be a bronze "Top Hat" bush which runs on this special bolt, which I can see in your photo, and in turn, a tube with an external key which runs on the top hat.

This allows a pair of gears to be keyed together, separated by that little washer with a slot in it. The whole assembly then sits on the banjo to the left of the headstock, and allows an intermediate pair of gears in the drive chain.

I hope this reads OK as it's not easy to describe without pictures.

Further edit of my post; I's say these are probably surplus to your immediate requirements, subject to the warning I gave above regarding the gear just below the Tufnol tumber gears.

Assuming you will at some point need to cut metric threads, it is possible on an imperial gearbox lathe by changing the initial drive gear in the chain. i.e. the one that sits on that keyed boss in your first photo.

Bill

Edited By peak4 on 25/11/2017 21:49:31

Edited By peak4 on 25/11/2017 22:13:57

Hi Piero,

You have identified the tumbler stud sleeve gear 10351. This replaces the 12 tooth ganged tumbler stud that is fitted on your machine as you seem to have worked out. On a more modern machine your 12T would be a 24T and the 10351 part would be a standard part. Your gearbox needs the 12T you have to operate correctly. Its a left over from the ML7 days. The washer in your picture will be 50 thou thick and along with the shaft piece are part of the metric conversion kit, which must have existed with your lathe at one time along with a set of gears which DO NOT form part of the current metric conversion set as the external gearing on your early gearbox is different.

You have previously said that you want to work in imperial, not metric. You can cut short metric and BA thread approximations with what you have by fitting the 10351 plus 20T, 21T, 33T or 34T (mostly the 33 & 34) onto the 10351 part. If you want to cut more accurate metric threads, then you need the metric conversion set, but you would have to supplement the supplied cogs in that set to cut all metric threads on your early gearbox.

Various mails on here talk about rough Myford metric screwcutting using the gearbox. I have deleted our previous correspondence and repeat my e-mail in a PM if all is not clear now.

Dennis

Edited By DMR on 27/11/2017 16:23:23

Edited By DMR on 27/11/2017 16:24:19

Couple of things spring to mind:

If I've understood that the gearbox train input gear is 12 T mot 24, then this is the old gearbox and the 20, 24, 33, 34 gears are a red herring. There is much buried in the archive to explain further, for example **LINK**

Also the idea that the 33 or 34 t gears give a "rough" approximation to a true metric conversion is wrong. They give a very close, useful method of getting to the "near enough" answer.

If the OP wants to adapt his lathe for metric threads and it is the old half speed g'box he needs the 17T or 16-1/2 T gears of the thread above.

Rgds Simon

Hi Piero, I think the best answer to your question about where do the bits fit is to suggest you need a copy of Brian Wood's book, Gearing of Lathes for Screwcutting, which gives chapter and verse on the subject. ARC have copies, and so did Amazon the last time I looked.

Essentially the gear train that carries the drive from the lathe mandrel down to the gearbox input gear is removed, and replaced with a selection of gears of different tooth numbers, all as per the appropriate label as above.

The standard banjo on which the gears are mounted isn't slotted, so this limits you to only using the original gears. To be able to use others (as per the label) you need the gears AND a different banjo. The one that Myfords sell, and which has been called the "Metric Conversion Kit", fits in place of the standard gear mounting carrier and allows change wheel trains to be built up in much the same way as you would in the old days before the quick change gearbox was invented. The difference here is that the slotted "Metric conversion kit" banjo lets you keep the quick change gearbox AND change the input ratios. That's what the labels above are showing.

The other half of the metric adaptor kit is a selection of change wheels of some funny looking numbers, as detailed on the labels above. If you would like to list the wheels you've got lurking in a box we can tell you what you can do with them, and whether they belong as a set with the metric conversion kit. (And for which version of the Q/C gearbox!)

Brian's book explains in more detail.

Myford users being inventive so – and – so's, along came the idea of keeping the original fixed spacing gear carrier, and changing the input gear (mandrel gear) to adapt the ratio between the mandrel and the lead screw. It happens that an extremely close approximation to the "correct" ratios can be achieved for a wide range of metric pitches just with a small handful of input gears. For the later gearbox, most of the metric pitches you'd likely want are achieved with a 33T and a 34 tooth gear, mounted on the 10351 tumbler adaptor as detailed above. John Stevenson pioneered this, and the gears to do it need are available from Myford. But it doesn't work for you and me – read on.

The big advantage of this technique is that you get to keep the fine feed ratios. If you fit the "metric kit" you lose the facility of the fine feed. The metric pitches you get are an approximation to the "true" metric pitches, but that's also true of the pitches you get with Myford's metric adaptor kit. Some of the approximate results are actually better than the original design, and (as Brian's book examines) you need to consider the limitations of the lathe's accuracy as well.

For your lathe – and mine – this doesn't work, as the early gearbox does not have the built in 2:1 speed reduction of the later gearbox, so if you set up the gear train as for the later box you cut a thread of twice the pitch you expect.

All is not lost, we know how to fix it. If you want to get involved with this we can explain further, but you really need to see Brian's pictorial explanation of what is going on first, as the adaptations to make it work with your earlier gear box assume an understanding of the overall system and also some rather creative gear cutting which John Stevenson devised.

Hope this makes sense,

Rgds Simon