Boxford spindle thread type

[old martParticipant @oldmart]

The 1 1/2" x 8 spindle size is used on several lathes both in the UK and in the USA. Atlas definitely use a 60 degree thread, but do the British makers also use it or Whitworth form? Could somebody with a Boxford tell me which thread their lathe uses?

[old martParticipant @oldmart]

[peak4Participant @peak4]

Posted by old mart on 27/02/2023 20:27:59:

The 1 1/2" x 8 spindle size is used on several lathes both in the UK and in the USA. Atlas definitely use a 60 degree thread, but do the British makers also use it or Whitworth form? Could somebody with a Boxford tell me which thread their lathe uses?

I don't have a Boxford, but see P2 of this pdf
https://ia601004.us.archive.org/34/items/lathe-manuals/Boxford%20spécification.pdf

Also P2 of this one
https://ia601004.us.archive.org/34/items/lathe-manuals/boxford%20MkII%20plaquette.pdf

Bill

Edited By peak4 on 27/02/2023 21:08:44

[Grindstone CowboyParticipant @grindstonecowboy]

Mine is Whitworth, but I believe some of the very early ones were 60 degree form due to it being based on a South Bend model.

It's always made me wonder if some of the modern accessories – backplates, collet chucks, etc. – are truly 55 degree, or just a loose 60 and hope they fit.

Rob

[BazyleParticipant @bazyle]

A Southbend chuck backplate doesn't fit a Boxford. Simple.

[Speedy Builder5Participant @speedybuilder5]

I have a Southbend backplate and chuck which fits my BOXFORD which begs the question, was my SB faceplate actually a Bford one ?

Ie: Will a Boxford whit thread at 55degrees screw onto a Southbend 60deg?

Bob

[DC31kParticipant @dc31k]

Posted by Speedy Builder5 on 28/02/2023 06:34:05:

Will a Boxford whit thread at 55degrees screw onto a Southbend 60deg?

You are asking the question in slightly the wrong form in the same way that Bazyle's flat denial or the issue is conceptually incorrect (or at the least contains too many unstated assumptions).

Draw a theoretically perfect 1 1/2" 8 tpi thread of both forms (Whitworth and Unified). See where and how much interference there is.

That is a base line figure, but no actual thread produced by mankind will match those dimensions. Thus you can work out how far from ideal the 'wrong' threadform needs to be to allow it to fit.

[Michael GilliganParticipant @michaelgilligan61133]

An excellent response DC31K

I would just add, if I may, that for completeness it should be noted that Unified threads come in several classes of ‘fit’

Does anyone know what class South Bend used in the first place ?

The infamous ‘rationalisation’ of 1/4” x 20tpi threads for the camera/tripod connection springs to mind.

This document may be useful to the investigating team: **LINK**

https://allcivilstandard.com/wp-content/uploads/2019/02/BS-01580-1-2007.pdf

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

I knew I'd read it somewhere, Rob said the same. so I was pleased to find the reference straight away on lathes.co.uk My memory isn't completely unreliable!

The main dimensions of the original South Bend spindle, with its 1.5" x 8 t.p.i. nose, were unchanged, and indeed stayed the same on the ordinary V-belt drive Boxfords until the end of production. An interesting note in the Company's records states that: From Serial 1360 all machines have an 8 t.p.i. Whitworth form spindle nose – a reference to the fact that the first batch must have had an exact copy of the South Bend fitting with its American 60° thread angle (the Whitworth is 55&deg.

My advice is to measure it. My soul revolts against the idea of screwing Whitworth into Unified on a precision lathe, but Model Engineers often bodge to their own satisfaction.

Dave

[HopperParticipant @hopper]

There have been threads on this topic before and some people have found that chucks off South Bends will not fit on to a Boxford. Others may have found differently, I don't remember.

It does depend to some extent on production tolerances,  amount of thread truncation and 50-plus years of wear as to whether there is enough clearance for two dissimilar angle threads to screw together. Only way to know is to fit and try.

If purchasing a chuck or faceplate sight unseen, it would be far safest to purchase like for like. Get a Boxford chuck for a Boxford or a US Atlas chuck for a US Atlas etc.

There is the option of running a tap down the chuck thread to make it match your spindle thread. Tracy Tools has most of the common spindle sized taps. Or even set the chuck up carefully on a faceplate and take a very light screwcutting cut down the thread to clean it up to correct matching spec. You can cut a 1:1 ratio thread (8TPI) without damaging the change gears or leadscrew etc. Done it more than once. Not a drama.

 

Edited By Hopper on 28/02/2023 09:18:57

[Dave HalfordParticipant @davehalford22513]

Posted by Speedy Builder5 on 28/02/2023 06:34:05:

I have a Southbend backplate and chuck which fits my BOXFORD which begs the question, was my SB faceplate actually a Bford one ?

Ie: Will a Boxford whit thread at 55degrees screw onto a Southbend 60deg?

Bob

As the owner of an American Rockwell Delta 10" I can confirm that a Boxford backplate from RDG fits. I don't believe for one minute the spindle thread is Whitworth.

[vic neweyParticipant @vicnewey60017]

I have a South Bend 9" lathe, I bought a couple of Boxford small parts to restore it inc the spindle for the carriage traverse wheel which was a perfect fit, also a screw cutting dial, another perfect fit, several change wheels to complete the set.

Then I saw a Boxford faceplate on Ebay at a good price and bought it and then found it did not quite fit and locked when partly screwed on.

I discovered the serial number of my lathe dates to 1939 but in 1940 they made a slight change to the mandrel thread and hence I can't use it unless I attempt to alter the faceplate thread slightly which so far I have not tried.

 

The South  Bend 9" is the worlds most copied lathe, over 20 different brands worldwide, but they all had permission to do it under the WW2 lend lease programme and Denford made the early Boxfords to this pattern

Edited By vic newey on 28/02/2023 09:51:39

[Martin 100Participant @martin100]

Going back maybe 10 years or so ago an ER32 spindle nose fitting collet chuck from a well known UK supplier didn’t fit either of my Boxfords, one dating from 1954, the other from 1960/61, nor did it fit a brand new spindle sourced from Boxford themselves. The thread of the spindle in all cases is 55 deg, 1.5” x 8tpi

The collet chuck measured something very close but didn’t thread more than two turns. The replacement was just the same. The supplier said they had no others returned. Suspected the collet chuck might be a Southbend 60 degree one but couldn’t be bothered wasting any more time as a job needed doing so I just bought a backplate and one of these

**LINK**

[Bob SillitoeParticipant @bobsillitoe83708]

Hi All,

I have the Southbend version of the lathe, with the correct backplate. If I buy a new Boxford chuck and back plate can I discard the new backplate and fit the replacement chuck to my Southbend backplate?

Thanks

Bob

[Howard LewisParticipant @howardlewis46836]

In my experience, Whitworth bolts don't like screwing into UNC holes, but a UNC will screw into a Whitworth hole.

Our Chief Engineer would not use anything other than Whit form fasteners. So when we came to Clayton Dewandre items with UNC threads, we had to tap them to Whit form!

Mot good practice in my book, but it kept the vehicle on the road

Howard

[Author]

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