Hi Eddie,

Welcome to the forum. There was a thread on the forum about the Stringer EW lathe, see here.

Thor

Edited By Thor 🇳🇴 on 16/07/2023 19:26:02

Yours came with gear cover? That's a rarity! Mine has all the optional-extras but that.

Setting up for screw-cutting is as on any lathe with change-wheels, but limited to two options:

Spindle pinion – idler – leadscrew wheel;

and

Spindle – intermediate driven wheel + intermediate driver – leadscrew.

They cannot be set for fine feeds – were never designed to be. And the single-piece nut means you need reverse the machine for the next cut. For cutting short threads it's probably best to use a mandrel handle, with the motor safely isolated and the drive-belt slacked off, and back-gear engaged.

Other than that they will cut a goodly range of threads properly, and with a lot of trial-and-error calculations, quite a few others to fairly close limits over a short ( <10 turns) length.

The standard formulae apply:

Leadscrew tpi (8 on these lathes) / thread to be cut = Spindle pinion teeth count / Leadscrew wheel teeth count;

OR

That but LS / work = (spindle / 1st stud wheel ) X 2nd stud wheel / LS wheel.

So for 16TPI:

8/16 = 20/40

and for 26TPI:

8/26 = 4/13. Multiplying by 5 immediately gives 20 / 65. (I think the EW change-wheels include a 65T wheel.)

So 20T spindle, any convenient idler on the banjo stud, 65T wheel on the leadscrew.

.

For 32 tpi you'd need a compound train:

8/32 = 1/2 X 1/2, e.g. by 20T spindle, driving the 40T wheel on the stud, that combined with the 30T wheel that drives the 60T leadscrew wheel.

i.e. 8/32 = (20/40) X (30/60).

The intermediate two wheels are linked by a little driving-pin in the hole next to the wheel's shaft-bore. (Myford and bigger lathes tend to use a key for that.)

.

You'll find these calculations in almost any book on turning that deals with change-wheels, and it's just a matter of adapting them to the change-wheels you have.

Cutting mm threads would be more of a challenge, but not insuperable. Some will calculate near enough for removing most of the metal by screw-cutting and finishing with a die in a tailstock die-holder. Though for small threads (<M6) it may be easier to use a die anyway.

If you need augment or replace any of the change-wheels be careful as most modern gears are of 20º pressure-angle. Those on older machines like the EW Lathe may be of 14ºp.a. They will mesh, if the same pitch, but not properly, risking harming both.

NB: It is very bad practice to try to cut threads the same or coarser than the lead-screw, especially on a small, rather delicate lathe like the EW. It puts very unfair stresses on even a large machine.

It can be done with care on a larger machine by driving it manually, from a leadscrew handwheel, but I would advise nothing coarser than 12tpi, maybe 10tpi (1" BSF), and with very light cuts on the EW.

'

Some owners have adorned their elderly EW lathes with all sorts of elaborate modifications like stepper-motors, but I prefer to keep my older machine-tools as original as possible. If I want that sort of sophistication I'd buy a sophisticated machine, but each to his or her own!

Try this site for a various ideas on EW lathes and mods if you want for improved screw-cutting

http\modelengineeringnorge.weebly.com

There is a screw-cutting table for EW on the site (I would post it here but it is too much of a bloody faff)

M.

(had a memory refresh!)

note this is for the original 16DP change gears (why 16  wtf? had they lost the smaller cutter?)

Edited By Martin of Wick on 17/07/2023 09:00:26

Edited By Martin of Wick on 17/07/2023 09:02:44

Not a ‘lathe-work’ book per se, but a/the book by member Brian Wood seems to be a useful tome (but neither particularly large or weighty!) for sorting out all sorts of thread cutting settings/scenarios. I’ve not read it but his book regularly receives a hearty recommendation on the forum.

Well precisely, not so much for finer threads but a more compact gear train using less material and better matched to the size of lathe, as well as the facility for a more reasonable fine feed using 70-80 tooth gears.

However, for the enthusiast, the Norwegian engineer site provides a good explanation and mod for a banjo that allows double compound using DP16 but needs more 65s for a fine feed(which could be 3D printed).

'Course, the big PITA that makes using this lathe rather tedious is really the full nut. I have seen solutions, but none have appealed to me as being particularly reliable.

So on account of 'elf n safety' to avoid RSI, my EW doesn't get used as much as it should be!