Welcome!
You have come to a good place, lots of expertise , help and advice on here, on all manner of subjects.
I am assuming that you are a newbie. If not, accept my apologies for teaching granny to suck eggs.
I have never owned a ML4, but have had dealings with a couple, getting one up and running again
There are folk on here who are more knowledgeable than I on the Myford ML 1, 2, 3 and 4 lathes.
The Lathes UK website is good for history and info on these lathes
The Serial number is usually on the bed, below the Headstock, and that can guide as to the year of manufacture., between the late 30s and mid 1940s.
The Tailstock is 1 MT. You can get drill chucks and arbors from suppliers such as Arc Euro Trade.
As you will already know, the Saddle handle turned clockwise runs the Saddle towards the Tailstock, unlike most lathes. Tumbler Reverse was an optional extra, so not all have this feature.
The Top and Cross Slide Leadscrews are 12 tpi, and each of the 80 division on the dials are not an exact thousandth of an inch, (0.00104 Actually )
The early ML4s had a 7/8 BSW (7/8 x 9 tpi ) thread on the mandrel, and later on this changed to 7/8 x 12 tp. I believe that some of the very latest had the 1.125 x 12 tpi thread, but not the 1.250 register, used on the 7 Series.
For what my advice is worth, I would not disturb the Headstock bearings, but cutb off the worn belt and use link belting such as Nu Twist.
Hopefully, you will have a complete set of change wheels. They should run from 20T to 65T in 5T increments
It would be worth acquiring some extras, so that you have three 20T wheels and an extra 60T.
With these, you would be able to set up a fine feed using a 20:60/20:65/20:60 train which will move the Saddle towards the Headstock in the "normal" way with a feed rate of 0.00427"/rev. You might need to make up another stud to carry one of the compound gears, and do a little fettling of the slot in the banjo to allow all the gears to mesh. To get a correct
Gears from the later ML7 Series can be used, but since yours are driven / compounded by means of 3/32 pins. The 7 Series gears will need to be drilled partway through for the pins (7 Series gears have keyways, but are the same 20DP and 14.5 Pressure Angle, and 5/8" bore. )
The threads are Whitworth form, some (such as the grubscrews ) are 1/4 BSF, while some, such as that securing the banjo, are 5/16 BSW. The locknut for the Tailstock adjustment (across the bed ) is 1/4 BSW.
Being an old machine, it is not suitable for high speeds, so carbide tools are not needed. High Speed Steel is probably an advance on what was used when the machine was first launched
So, if you do not have one, you are in the market for a bench grinder, and learning how to grind tools.
It may be a useful learning exercise to make a Centre Height Gauge. You will,become more familiar with the lathe, and gain confidence. the gauge will make tool setting much easier.
To cut properly, the cutting edge of the tool needs to be on the centreline of the work.
How to grind a tool?
"The Amateur's Lathe by L H Sparey, "The Amateur's Workshop" by Ian Bradley will be useful books.
A set of Zeus charts will be most valuable And a very useful reference book is Tubal Cain's "Model Engineers Handbook"
All there will be money well spent, and a source of useful information in the days ahead,
Riding one or more of my hobby horses, I would avoid using the "boat" type tool holder. If used, by tipping up, to set the tool to centre height, it changes the top rake, which may not be a good thing to do. My preference is to grind the top rake, if you want or need it, into the tool and to keep the holder horizontal, shimming to set at centre height.
My other hobby horse is to use a Tangential Turning tool. There have been at least two designs published in MEW to take 1/8" square toolbits, which would suit the ML4 You can buy a more sophisticated version, see the adverts on the side bar. For these, you will need a Centre Height gauge to set the tool. Sharpening is easy since there is only one face to grind, and the grinding jig is simple. Whichever, the tool works well.
HTH
Howard FAT fingers AGAIN!
Edited By Howard Lewis on 01/01/2021 14:43:31