Alternative to backplates

[Darren]

I'd really like a faceplate and 3 jaw chuck on my Smart & Brown lathe.

Trouble is it has a 2" dia threaded nose and ready made plates are almost as rare as Dodo's

I have found one in two years of constant searching and this currently holds my 6" 4 jaw chuck.

But I was thinking, Uh oh.....

I have a couple of these, one in 50mm and one in 100m dia


Do you recon I could mount a chuck to the larger one and thread the smaller one to take a 1/2 threaded faceplate I have from another lathe?
Or even a Myford thread, as there is all sorts avail for these?



The real question is would a 5C fixture be up to the task  it looks pretty tough to me, but i though I'd throw this one out to the wind and see what comes back?

[Darren]

Aww, forget the last idea, I have no way of threading it, won't fit in the mini lathe.

But the 1st idea sound feasible?

[bogstandard]

Darren,

I wouldn't like to go too large a chuck size.

On the ones I used for converting to Myford nose, I kept the largest to 125mm, and if you saw my post, I made a basic faceplate out of the same sized backplate. Going over that is really putting a large strain onto the fine threads of the 5C system.

John

[Darren]

Thanks John,

Isn't the 5c locked by a keyway? Mine is, the threads just pull it back.

I don't think I'd trust the mass of a big chuck but maybe a slimline one kept down to 100 or 125mm dia.

Oooh, I wonder if I have the power to used this?

Doubt it.....

http://cgi.ebay.co.uk/MYFORD-HEADSTOCK-NOSE-THREAD-DIE-1-1-8-X-12-BSW_W0QQitemZ260345165436QQcmdZViewItemQQptZUK_Home_Garden_PowerTools_SM?hash=item260345165436&_trksid=p3286.c0.m14&_trkparms=66%3A2|65%3A7|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

[bogstandard]

Darren,

It isn't just the threads, it is all of it. Because it isn't a solid lump, it will be nowhere near as strong as if it was all one solid spindle. That is why I kept mine down to the smaller sizes and do no heavy cutting with them.

I saw that die when you showed it earlier. Really, what you should do is single point the thread roughly to size, then finish off with the die to give the true thread form. If you try to cut in one go, just using the die, you only have to be a gnats out of square and you will be in deep doodoo.
Really, the best bet would be to mount the blank into your 5C carrier, then cut the thread using single point. But rather than Myford, I would use something like a Boxford thread, which is the same as Atlas, some South Bend and a few other large lathes. That would then give you access to much cheaper second hand nose fittings, rather than Myford, which tend to be expensive even second hand, purely because of the name.

John

[Darren]

Thanks John,

Can't cut threads on this lathe, that's the whole point.

OK it was worth a thought, small chuck or nothing it is then. Good point about Boxford threads, arn't they square?

[bogstandard]

I'd forgotten about that Darren, it is so long ago since we discussed it.

I think then we talked about me making you a new spindle, but you would lose your 5C nose taper.

Boxford threads are standard triangular shaped. 1.1/2" x 8TPI.

Maybe you spindle nose could be modified. Without measuring up, I wouldn't know if it is possible. It is the 5C nose taper that would be the deciding factor.


Otherwise, back to the drawing board.

John

[Darren]

John,

It's the 5C that made them change their standard size from 1 3/8" to a 2" thread. To make room for the 5C from their own smaller collets. Shame they didn't up it a tad more to 2 1/4 as there are quite a few other lathes that use this size.

I really don't think you'd be wanting to make one of these, but then again I know you like a challenge 

[bogstandard]

Darren,

I have just been thinking, if you could wait a while, until I am back on my feet, my 5C is ground to be super accurate (no detectablle runout at all). It would be no big job to mount it onto my lathe, and single point cut it to any thread you needed.

All you would need is either a die like you showed, or say a backplate of what you wanted to use. I think pre made boxford backplates are readily available from RDG.

Then you could use that as a basis for a complete range of chucks or faceplates, as long as you weren't doing any super heavy machining, it should work ok.


John

[Darren]

Bogsy, you did mean this thing didn't you



Cos here's a description of the spindle

"By 1954 two additional headstocks were being offered, the PRH/1 and LPH. The PRH/1 could mount standard 5C collets and had a nickel-chrome steel spindle, case hardened and ground on
all working surfaces and running in special high-precision anti-friction bearings."


Thanks for the offer, I may just be knocking on your door when you wake up......take care in the meantime 

[John Stevenson]

I have a 4" 3 jaw SC chuck mounted on one of these.
had it ages, bought from J&L, comes in handy at times especially when the infernal jaws on the 6" or 8" chuck are too big to go into somewhere.

I have bought a few of these blank 5C's over a period of time for specials, the 5C to ER 32 collet chuck that ARC sells started life as one of these.
I also have a 5C to Myford thread for odd jobs as well, but the thread and register won't fit the blanks as sold - too short

JS.

[bogstandard]

Yes Darren,

That was what I was looking at, but John has just put the dampener on it as he says they are too short to machine the thread and register on them, and he should know.

So really, if you get one at 2" diameter, extend the blank bit on the end (threaded and with engineering adhesive) then machine it to size required.  I should think there would be no major problems as most to the pressure is taken on the back face and register.

Or do as you originally planned, and fit a 4" chuck onto the larger one by treating it as a backplate, but that is admitting defeat.

John