EW Stringer Lathe Spindle Thread

[James AlfordParticipant @jamesalford67616]

I picked up an EW lathe today. Does anyone know what thread the headstock spindle is?

Regards,

James

[James AlfordParticipant @jamesalford67616]

Following on from my spindle thread question,  would anyone with a Myford ML8 mind measuring the register OD, please? I am wondering whether a ML8 faceplate will fit the EW lathe.

Thank you.

James.

 

[IanTParticipant @iant]

It’s 1″ x 12tpi James

Regards,

IanT

 

[Martin of WickParticipant @martinofwick]

You will need to consider more than simply the thread pitch, ie, depth of thread and depth of register may be significant. The commonly available 1” x 12 pitch backplates can be made to fit, but some reduction in overall thickness of the casting is required, otherwise it is hanging on by a couple of threads!

[Martin of WickParticipant @martinofwick]

And should have added need to sleeve down  the register area to 1″ from 1 1/8 (which may also be the case for ML8 faceplates) but someone may be able to confirm.

[James AlfordParticipant @jamesalford67616]

Thank you, Martin and Ian.

That is helpful. It sounds like there will be a fair amount of work to get a Myford faceplate to fit the EW, which is a shame, but not unexpected.

I think that it will have to be a job for another day as I have other jobs that are more pressing, currently.

James.

 

[Nigel Graham 2Participant @nigelgraham2]

Probably easiest to make a faceplate completely anew, from a blank. Do that, and you can also arrange and size the clamping slots or holes as you think best. The originals for both EW and Myford would be of cast-iron but I don’t see a problem with using mild-steel – except perhaps risking wearing the spindle as well as the plate – or even aluminium-alloy.

Turn raised rim on the rear to give a stiffening flange.

Thread 1″ X 12… but from measuring my lathe I could not decide if of Whitworth or Unified form! The BSW thread-gauge fitted much more comfortably than the UNF one, but of the standard threads, 1″ X 12tpi is UNF.

I have just investigated what Tony Griffiths can tell us, and the spindle thread is the one detail omitted. I did discover mine is the Model D – i.e. back-geared and screw-cutting.

 

[IanTParticipant @iant]

This may help James….

Courtesy of Alan @ Model Engineering Norge (which is a site any EW owner should check out)

 

Regards,

 

IanT

 

 

[Nigel Graham 2]

On Nigel Graham 2 Said:

 

Thread 1″ X 12… but from measuring my lathe I could not decide if of Whitworth or Unified form! The BSW thread-gauge fitted much more comfortably than the UNF one, but of the standard threads, 1″ X 12tpi is UNF.

 

 

Standard threads such as 1″ x 12tpi UNF etc are for fasteners (nuts and bolts). Special machine parts will commonly use “special” threads where the thread form (cross-section) is adhered to but the number of TPI is chosen to suit the maker’s needs, not to adhere to the standard fastener charts. So it is most likely a BSW thread form, being made in UK. (But not necessarily!)

[Howard LewisParticipant @howardlewis46836]

Use thread gauges to check that the thread angle and pitch conform to the drawing above.

Not knowing the lathe, guess that it is quite a few years old, and if of British manufacture, would expect the thread form to be Whitworth.

Assuming the aim is to produce a backplate , or catch plate to screw onto the sapindle, the most likely option will be to screwcut the thread. Thread depth will be 0.0534″

Tracy Tools do not show a 1 x 12 tpi Tap in their ncatalogue (It would take a lot of torque to drive one anyway.

You could rough it it out and then finish it with a thread chaser, or a single cutter from a Die Head, (In a  0.8932″ bore there may be enough room for a single single Die Head cutter).

You could make a plug gauge to check the internal thread, using the thread on an existing backplate as a gauge to check the thread on your plug gauge, as you make it.

The item will be located by the 1.000″ register, so the thread is to pull it into place, so ABSOLUTE precision of the thread is less vital.   Once in place, on the spindle, the final machining of the OD and the face and register for the chuck can then be done to maximise concentricity.

Howard

[Nigel Graham 2Participant @nigelgraham2]

You won’t find a 1″ X 12tpi tap of BSW or BSW form, but anyway at that size a tap is best used to finish a machine-cut thread to size and profile.

I have not tried it, but it is possible to cut an internal thread by using one “edge” of a tap in a suitable holder as a chaser, and here 12TPI Whitworth form are 3/4″ BSF, and 1/2″ and 9/16″ BSW.

Holding a 1/2″ BSW tap against my lathe’s spindle and in the back of a chuck suggested this could be feasible. Probably best to experiment first on a bit of spare material to ensure the settings etc. are all spot-on as rotating the tap in the holder will affect the cutting-edge height as well as the top rake and clearance.

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