ML 7 Acme threads,

[David Bothwell 1Participant @davidbothwell1]

Wondering if somebody could help, how to set the gearbox for acme thread on ML7 (for crosslide screw manufacture? also thread position indicator (4 position on leadscrew) will not turn when engaged, it turns when stationary, but when lever engages drive it refuses to turn, I have cleaned and oiled it, but I could not disassemble it! Any suggestions most gratefully accepted, Seasons greetings to all,especially thos providing previous assistance. Wouls I be better off buying an ace die?

[David Bothwell 1Participant @davidbothwell1]

gearbox setting and 4 position indicator

[JourneymanParticipant @journeyman]

Acme threads are only special in respect to their shape, you need the correctly profiled tool-bit. The TPI or pitch if metric will be as for any other type of thread. Just look at the thread cutting chart on the headstock!

As to the threading indicator dial not turning, that's how it works. Select the line to engage and when it comes into conjunction with the fixed point engage lever and it will stop turning.

John

[RobCoxParticipant @robcox]

When the half nuts are engaged the thread dial indicator shouldnt rotate. It indicates the position of the leadscrew relative to the cross slide, which is constant with the lever in the engaged position.

Acme thread cutting is best done single point IMHO. The threads, even 10tpi, would require a lot of effort to cut, and probably wouldnt end up straight. The width of cut becomes quite large and in my experience controlling chatter is an issue.

The change gears are set up for the thread pitch, irrespective of the thread form. Cant help you with the choice of gears though, as I dont have a myford and you havent specified the thread pitch.

Rob

[David Bothwell 1Participant @davidbothwell1]

Many thanks for the replies and advice, I am a bit confused as to the info on the dial indicator I thought that when the saddle lever was engaged the dial indicator travelled wih it?

[JourneymanParticipant @journeyman]

Just to be sure, when you say dial indicator, I take it you are referring to one of these:-

It's sole purpose is to make sure that the leadscrew is engaged at the correct time. Depending on the thread TPI/pitch and the leadscrew TPI/pitch it will be possible to engage the feed at any line, two opposite lines, just one line or for some metric pitches it wont work at all.

John

[Pete RimmerParticipant @peterimmer30576]

I'm going to presume that you are wanting to make a new cross slide screw for your ML7 which is 10tpi. Being an even numbered hread you can engage the half nut on any line on the dial numbered or not.

[David Bothwell 1Participant @davidbothwell1]

Hi Journeyman, that is the indicator I meant, thanks for the replies, still tryong to convert your explanations!!! I will get there though

[BazyleParticipant @bazyle]

Do you absolutely have to do this at this time, with your level of experience? Is it missing off your lathe? If it is just about backlash have you bought a new nut? It is quite a difficult item to make, let alone make well and a lot of the people on the forum would work hard to avoid such a task.

[David Bothwell 1Participant @davidbothwell1]

It is not an absolute requirement, but there is significant backlash, as for my level of experience I have owned the ML7 for over twenty years, beyond that I had my first experience pn a metal lathe when aged fourteen, in 1958! Although I need some advice/help (due to my age I expect)

[JourneymanParticipant @journeyman]

Ah, now we know what's being made. Cross-slide leadscrew for an ML7. As Pete says, you can pretty well ignore the indicator lines for a 10 TPI thread although probably as well to choose one line and stick to that just for good practice at engaging the feed as required. Don't know exactly how long the screw is but a flimsy long item like this will probably need the use of a travelling steady to stop the job springing away from the tool. I would be inclined to single point the thread and then possibly make use of a suitable die to correct the thread form. Definitely hard work to do the whole thing with a die. Doing single point cutting will ensure the correct and accurate TPI over the length of the thread and then the die will clean it up nicely.

John

[Howard LewisParticipant @howardlewis46836]

Stupid question, but you have slackened the 1/4 BSF nut so that the Thread Indicator Dial can swing to engage with the Leadscrew, before retightening it?

Once engaged, as the Leadscrew rotates, it will drive the dial, so that you watch it rotate, and close the half nuts at the appropriate reading.

If this is all Greek to you, I would advise reading up on screwcutting before cutting metal for real (By all means experiment, so that you gain the experience and confidence to do the job well when the time comes to do it in anger. )

It's a bit late, today, to ask Santa to bring you Martin Cleeve's book, No.3 in the Workshop Practice Series, "Screwcutting in the Lathe" but I would expect that you would find it a help, now, and in the future.

If the problem is one of excessive backlash, ( > 0.020"? )a new mazak nut may improve matters considerably..

Being soft, it is more likely to wear than the steel :Leadscrew, and can easily be replaced..

No doubt RDG, who now own the Myford brand can supply, at relatively low cost.

HTH

Howard

[David Bothwell 1Participant @davidbothwell1]

Many thanks to all, merry Christmas and a happy and useful new year!!

[Howard LewisParticipant @howardlewis46836]

Just looked at the Myford Spares site.

A new Imperial nut will cost you about £18, a new Imperial feedscrew and nut will set you back circa £41.

Postage is said to be free.

Howard

[David Bothwell 1Participant @davidbothwell1]

Hi Howard, Thanks for the info, I have not been able to find one so cheap, so I will take a look. FOOTNOTE to my post, I realised how the indicator works this morning ?(after all the advice) so my thanks, but I dont think it is worth all the effort!

[Howard LewisParticipant @howardlewis46836]

David,

You have a PM

Howard

[Tim StevensParticipant @timstevens64731]

Don't forget that there are other sources of backlash than the fit of the nut on the thread. How much slack is there between the end of plain bore and the face of the screw (one side) and the calibrated knob (the other side)? Taking this slack up as much as possible is free, and takes a few moments, but I have found machines where this has been completely ignored or overlooked.

There are pictures in the manuals which should make this adjustment clear.

Cheers – Tim

Edited By Tim Stevens on 27/12/2021 18:19:09

[David Bothwell 1Participant @davidbothwell1]

THanks for that Tim, I have seen a mod on Youiube involves placing thrust bearings either side pf micrometer dial and inside, then saw a further mod placing a bearing between, but this involves some machining/alteration, not going with that!

[David Bothwell 1Participant @davidbothwell1]

THanks for that Tim, I have seen a mod on Youiube involves placing thrust bearings either side pf micrometer dial and inside, then saw a further mod placing a bearing between, but this involves some machining/alteration, not going with that!

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