Myford Super 7 Long Bed Big Bore Conversion

[Nick Hulme]

I'd been considering a larger lathe for some time, purely for greater through capacity.
I can't do without my lathe for more than the odd weekend though, and I didn't want to go back from a fully tooled lathe to shopping for tooling to complete a job.
To get where I wanted to be I would have needed to buy and fully tool a new lathe, and get it running well before I could swap it over and retire the Super 7, after that I'd need to sell the Super 7.
Then I saw the big bore headstock advertised, it came (while briefly available) from Myford Stuff.
The 30mm through capacity and ER40 nose have transformed the lathe in use, rigidity is improved, parting is now a joy,

- Nick

 

[Neil Lickfold]

Where did you get the conversion kit, and did the headstock casting need to be replaced too?

 

[pete]

I don't know how Nick got his, but there's a thread here about someone in the UK doing custom conversions to the small bore super 7 head stocks to the large bore and ER 40 spindle taper. https://www.model-engineer.co.uk/forums/topic/myford-super-7-with-big-bore-conversion/ I don't know if he still is though. Maybe I'm missing it on the Myford Lathes website, while they show the big bore super 7's, there doesn't seem to be any mention of the ER 40 spindle taper option.

 

[Nick Hulme]

I don't know how Nick got his, but there's a thread here about someone in the UK doing custom conversions to the small bore super 7 head stocks to the large bore and ER 40 spindle taper. https://www.model-engineer.co.uk/forums/topic/myford-super-7-with-big-bore-conversion/ I don't know if he still is though. Maybe I'm missing it on the Myford Lathes website, while they show the big bore super 7's, there doesn't seem to be any mention of the ER 40 spindle taper option.

For reasons no one ever explained Myford never embraced the native ER40 spindle nose in their big bore model (still only 1" clearance through capacity)

 

[pete]

It's a bit unclear how the ER 40 nut on yours works Nick. Is there an adapter for the usual Myford spindle thread or a custom ER 40 nut using that thread?

 

[Nick Hulme]

It's a bit unclear how the ER 40 nut on yours works Nick. Is there an adapter for the usual Myford spindle thread or a custom ER 40 nut using that thread?

The spindle has an ER 40 internal taper and and ER40 external thread.
Behind the external thread there is a shoulder register allowing the backplates to fit in the same way as Myford backplates fit, just bigger, and using an ER40 thread.
This allows an ER40 collet and collet nut to fit directly to the spindle nose, beautifully accommodating round parts and round stock with excellent accuracy and repeatability.

 

[pete]

Ok that makes sense now, thanks for the extra details Nick.

 

[Jasonb]

What do you do about mounting say an Morse taper Ctr or other tooling? Does it have an adaptor ER taper to MT or do you just use parallel shank and grip it all in an ER collet?

 

[Niels Abildgaard]

The spindle has an ER 40 internal taper and and ER40 external thread.
Behind the external thread there is a shoulder register allowing the backplates to fit in the same way as Myford backplates fit, just bigger, and using an ER40 thread.
This allows an ER40 collet and collet nut to fit directly to the spindle nose, beautifully accommodating round parts and round stock with excellent accuracy and repeatability.

I put a homemade spindle with 28mm hole,ER 40 thread and cone in a cheap chineese 180 lathe.
Cone and thread was machined in situ the Schaublin way and surprisingly accurate.

Cheap and accurate

The screwed on four chuck was once started fast in reverse.
I swore never to use screwed on chucks again after thevery unpleasant shock.

My next and present lathe based on Cheap Chinese 180/210 has 48mm bore and a 95 mm corner again made in situ,as have my ER40,four jaw,three jaw and face plate.

If I ever need more accuracy a four jaw or a loose fitting ER40 collet chuck will be used.