Reverting An ML7 To Change-Wheels: Any Thoughts??

[Nigel Graham 2Participant @nigelgraham2]

Cracked it, with help from Peak and I think DC31k, on another’s similar question.

The Manual for the gearbox had me totally flummoxed for a while, then I realised today my ML7 is almost there, for cutting metric threads. I am not sure about the BA threads and worms (DP and Mod. threads) tabulated in the Manual.

The gearbox uses a particular type of banjo with studs on fixed centres and only angular adjustment.

The secret is that you swap the normal inch-based gear-train on those studs with another, and set the gearbox to positions not the TPI numbers.

It’s a bit of a half-way house solution – change-wheels plus gearbox – and if you wanted to cut a wide range of both metric and inch-based threads, not much more efficient than using change-wheels throughout, especially as Myford stock a 127-tooth wheel.

I did not realise that special banjo came with the gearbox, so is already on the machine; and when I looked harder this afternoon I saw in fact the chart for all this is there inside the hinged gear guard.

 

I listed all the gears I have, determined which are missing from the collection (only a couple of them), so come MMEX….

[peak4Participant @peak4]

Just remember to keep the leadscrew half nuts engaged when cutting non-imperial threads.
Reverse the motor and return the carriage for the next cut that way, rather than using the threading dial.

Bill

[duncan webster 1Participant @duncanwebster1]

Get genuine Myford ones, I bought some pattern ones and they were well undersize even though they had the right tooth count. Supplier refunded without question, so must have been a known issue

[Nigel Graham 2Participant @nigelgraham2]

Peak4 –

Thankyou. Yes, indeed. For a short thread such as a stud it’s often safer and easier to slip the driving belt off and rotate the lathe by hand. Though I’ve not had much luck with one of those handles that reputedly grip the inner wall of the mandrel.

I have a note giving the thread-dial instructions and that half-nut warning. Hand-written, protected by a polythene bag, on the splash-back well away from the worst of the muck.

 

Duncan –

Thanks for that tip. I will buy from the Myford stand.

[Howard LewisParticipant @howardlewis46836]

Many years ago, when I had a ML7, I had a 127T changewheel. As you might imagine, it was big, (6.45″ OD) preventing the gear cover from being fully closed.

My present lathe, (which is Metric)  has a 120/127T idler.

In both cases changing between Imperial and Metric is simple, just getting greasy hands.

If you can find / make a 127T gear things should be simple.

Although for most smaller Metric threads, I use Taps and Dies (The Die holders came from Arc Euro, and the bodies are a slightly loose fit, to allow self centering, on an arbor held in the Tailstock)

To make some ER collet holders, obviously, I had to screwcut 1.5 mm pitch threads

Howard

[Nigel Graham 2Participant @nigelgraham2]

Finding a 127T change-wheel for a Myford ML7 seems simply a matter of contacting Myford! It is listed, along with many other “in-between” sizes.

In fact the various suggestions on this thread directed me to look more carefully at the gearbox’s rather unclear operating-manual, and at the machine itself. This suggests cutting metric threads is a matter of changing the change-wheels between the spindle and gearbox input, on the gearbox’s particular banjo.

I’d feared it would need a special banjo I don’t have and is no longer made.

The gearbox banjo differs significantly from that used for change-wheel only operation, in having fixed studs and only a short angular adjustment.

If I have read the book correctly, there was a second type of special banjo that allows BA and all manner of unusual pitches; but if you are likely to be cutting a huge variety of threads you may be better with a conventional all-changewheel set.

The gear cover holds a chart of the relevant wheels for mm pitches in 0.25mm steps to 3mm; though because its diagram is reduced to fit the space, it is not obvious which way round two pairs of the wheels are arranged.

The manual also specifies how to cut diametral and modular pitches (for worms).

 

Obviously the gearbox settings are then by position, not by the thread pitches marked on the label.

 

Using taps and dies is the easiest approach for small threads, but they do need suitable tool-holders and I think this perhaps my best route. The commercially-made die-holder I have does not work properly on my Myford lathe.

Sometimes, it’s necessary to reduce the diameter of the rod a little before threading it, and I have what I think is called a “stripping” or “running-down” tool, originally for a capstan lathe, I could bring into service for that duty.   It’s a small tool-holder combined with a steady formed by two bearing races on adjustable arms, all on a block with a drilled-through stem for a tailstock chuck. It takes up to about 1/4″ diameter rod, I think.

[Charles LamontParticipant @charleslamont71117]

I bought a 127T change wheel. It has never been used. Instead, I use Duncan Munro’s gear calculator to find extremely close pitch approximations making use of more sensible sized wheels that I can close the gear cover over.

https://metal.duncanamps.com/software.php

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