EW Stringer Lathe Spindle Thread

[James AParticipant @jamesalford67616]

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

Regards,

James

[James AParticipant @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 AParticipant @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.

[James AParticipant @jamesalford67616]

Thank you for the drawing and for the advice and suggestions for checking and cutting the thread. The drawing is escpecialy helpful.

I think that this will have be something that I shall have to pay someone to do for me as I have no facility for screw cutting. My Flexispeed has no change wheels and neither does the EW.

Regards,

James.

 

[Martin of WickParticipant @martinofwick]

James,

not having a set of lathe change wheels is a major PITA, compounded by the fact that the EW deploys 16DP (absurdly OTT for a lathe of such small capacity). If Mr stringer had used something more sensible such as 20DP, you would be able to use the commonly available Myford Gears.

However, all is not lost…

if you dial in ….model engineering norge ew lathe.. or some-such into google, you should be able to find the v helpful site referred to above by ianT.

This site as well as having much useful info, also has a guide to an improved banjo design and optional extra conversion for DP20 gears which will significantly improve the utility of the lathe (I have implemented the revised banjo to give lower feed rates, but not made the full conversion to 20DP).

The other alternative is to make your own change gears. I have successfully used 3D  printed gears made from decent quality PLA (use traditional ‘rock hard’ PLA, not not the PLA modified for increased flexibility). Nylon would be better, but you will need a printer capable of running at 300c + and an a way of keeping the filament dry for optimal results.

Or cut your own, which will be a fabulously expensive and time consuming operation by the time you purchase/make the cutters and blanks!

As an extra thought, if considering a revised banjo, I don’t think it would be beyond the bounds of possibility to further adapt to use the commonly and cheaply available Chinese minilathe gearsets. You can get a set in metal for £ 60 to 70 on the Bay (ie less than a set of myford gears).  Clearly you will need to check what size can be adapted to fit on the spindle, then work out if the remaining selection will cover the pitches you are likely to use (including the feed pitches). They are module 1 gears, so easily available if you need to infill or a special (like a 21 or 63 for example).

BTW, Tracy Tools sell a 1″ x 12 whitform tap, but I would not advise attempting to hand tap at that size!

 

[Nigel Graham 2Participant @nigelgraham2]

Form a quick experiment with my own (I did not attempt a full train) you can use Myford change-wheels, with a new banjo stud to cope with them being slightly wider than the EW originals.

All you cannot do, is mix wheel sets!

I know many EW owners have modified their lathes but they were never intended to be used for self-acting feeds in original trim, with the standard change-wheels. This may be why they have permanently-engaged leadscrew nuts and a banjo giving only a two-step compound wheel trains.

[James AParticipant @jamesalford67616]

Thank you, Nigel and Martin.

That is helpful. I shall have a look for the model engineering norge ew lathe that Ian also mentioned.

The advice is much appreciated.

Regards,

James.

[Martin of Wick]

On Martin of Wick Said:

BTW, Tracy Tools sell a 1″ x 12 whitform tap, but I would not advise attempting to hand tap at that size.

It is not an easy task but I have just finished fabricating a mild steel backplate for a 3-Jaw chuck acquired recently on eBay. I recommend Tracy Tools for prompt service and sound advice, and have been using them since the 1960’s when they were located in Dartmouth.

When I contacted Tracy Tools regarding Whitform taps, having read this Thread, Russell Coates advised me to carry on & use the 1″ x 12 UNF Taps I had purchased from them many years ago but never used!…

I am please to report that the UNF taps were a great success and the new backplate fits perfectly. Obviously one of the most important elements is the turning of the 1″ diameter internal register which ensures the mounted chuck will be concentric to the EW Arbor. Similarly it was necessary to then mount the blank and finish turning the OD, and Raised Face to match the 3-Jaw chuck’s recesses.

My conclusion is that a 1″ x 12 UNF thread is absolutely fine and I am glad I listened to the sound advice received from Russell.

Hope this is of use to EW owners who may like me have felt unsure of how to proceed.

Andre

[old martParticipant @oldmart]

I bought an 80mm TOS (Czechoslovakian) three jaw  scroll chuck on ebay which came with two backplates, 1 X12 I believe. One had a big enough boss to turn into 1 1/2 x 8 to use on the Atlas but there was not enough meat to convert the second one. It is sitting somewhere at the museum, I will have a look on wednesday when I go back in. The backplates look like they are made from stainless steel, but machined and threaded easily enough. The TOS chuck is first class for a little one.

[Martin of WickParticipant @martinofwick]

Hmm… UNF included angle on thread = 60 degrees, Whitworth included angle on thread = 55 degrees.

So in the fist instance I would have expected some issues mating the threads but I guess if the threads are large and loose enough you will be able to screw one to the other, as you have proved.

Not the most rigorous approach but if it works, it’s a result and useful intelligence!

[Martin of Wick]

On Martin of Wick Said:

Hmm… UNF included angle on thread = 60 degrees, Whitworth included angle on thread = 55 degrees.

So in the fist instance I would have expected some issues mating the threads but I guess if the threads are large and loose enough you will be able to screw one to the other, as you have proved.

Not the most rigorous approach but if it works, it’s a result and useful intelligence!

Rigorous? I don’t have a shadow graph in my workshop so was unable to confirm actual flank angle on the EW. Frankly I’m not convinced anyone one else on this Forum has actually carried out such a rigorous type of inspection either.

You guess my fabrication is so sloppy as to allow the threads to mate badly, well I suggest you are way off the mark and somewhat presumptuous…

Andre

[old martParticipant @oldmart]

I have recently had difficulty with Whitworth verses UNC threads. When correcting the nod in the museum’s round column mill. The base of the column is bolted down by four 5/8″ coarse threaded bolts. They are 5/8 x 12 size, but it was not certain whether the threads were 55 or 60 degrees. A 1/2″ thick corrector plate with a very slight thickness difference front to back was to be fitted under the column. I found some 1/2″ longer bolts courtesy of a Rolls Royce donation of mainly aircraft engine goodies and some commercial items. The threads looked identical and no tell tale markings were on the bolt heads, either the old ones or the replacement ones. I ended up by trying a Whitworth and a UNC tap down the holes on the base casting. The Whitworth was finger tight at about 3 turns and the UNC could be screwed in all the way with just fingers and was not sloppy. So our Taiwanese made mill has UNC threads in it although the X, Y and Z movements are metric.

For a threaded mount spindle, the important thing is that the rear face of the backplate rests fully against the square face of the spindle. The angle of the threads will automatically hold the backplate concentric every time it is tightened. Both of the lathes at the museum have registers for the backplates that vary from +0.0005″ and +0.020″ and they all repeat perfectly. The tightest one is a pig to screw on because of it’s close fit. And that is for all twenty or so backplates that we have.

[Martin of WickParticipant @martinofwick]

Weeeeell Andre, difficult to see how I can be casting aspersions on your fabrication since you have used a commercial tap to cut the backplate thread! On the other hand, as you say, who knows how well the spindle thread was cut originally or what that thread condition is after 75 years.

According to my very non-rigorous jamming and eyeballing of both a 55 and 60 degree HSS cutting tool into the thread on my EW, the ‘least worst fit’ was for the 55 degree cutter, which makes my version of the EW a Whitform thread, in my mind. However, as you have conclusively proved, the thread included angle simply may not matter over such a short thread length.

Point is, be happy, you have provided useful information, it worked, it doesn’t jam, and all the rest is academic. I would happily use the same technique myself (assuming I have the strength required to twirl that size of tap!).

 

 

 

 

[old martParticipant @oldmart]

I doubt if I could manage a 1″ tap even with my 2 foot long tap wrench.

[old mart]

On old mart Said:

I doubt if I could manage a 1″ tap even with my 2 foot long tap wrench.

Have no fear, tapping a 1″ thread should never require brute strength; at 79 years old I could never be a Mr Universe contender!

I suggest just care & attention to preparation, use of the correct tools, attention to detail and a great deal of patience. All of which are also required to achieve the best results with an EW lathe. Well that’s been my experience having acquired my first gap-bed machine some time ago in the 1960’s…

I’ll come back later to elaborate on my approach to the 1″ UNF job…

Andre

[BB12Participant @bb12]

As promised, further notes on my recent experiences with 1″ taps etc. is covered here:

EW Stringer Lathe Backplate Fabrication

Andre

[Author]

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