Tough part configuration

[Kennebec]

Hello Swiss turn people,
I have an aquaintance who has a part 304SS 5/8 Ø x 42" long, Dog bone shape: at roughly 3-4" from both ends part is reduced to 3/16Ø that is 36 to 34" long between the 5/8 Ø ends. I think I see a video on one of these type machines were the part was fed out the spindle so the work is all done at the Collet face, but with this lenght there would have to be some provision to pickup the part as it extened out the collet.

Any ideas or info is greatly appreciated

[citizencnc]

From the sound of it, I'm sure this part can be done on a 16mm CNC Swiss type machine( I prefer Citizen because I know what these machines can do). There is no way you can pick up with the sub spindle to support while turning because of machine's stroke limit and the neck down of the part. However you can get the job done by being creative to come up with some kind of liner inside the sub spindle sleeve, something like a tube with an ID a little larger than 5/8 to keep the part from bending(or drop) due to the weight of the front end.
Let me know if you have any further question.

[hacdlux]

just a theory but here we go,
you start off all swiss programs with the cutoff blade holding the stock whike you re-chuck for stroke length

turn the 3/16 for the full stroke fo the machine
turn off the spindle
use the turning tool on the shoulder of the cut to hold position
rechuck
repeat untill length is achieved

you could also feed out some 5/8 past the gb grab it with the sub hold it , rechuck, release the sub, suck the material back in the gb and continue

citizencnc is right you would need a liner in the sub to hold it steady.
tsugami makes a long part ejection system for this kind of stuff

good luck

[glenthemann]

Well, on our L20, what you do is remove back spindle air post that goes into the back of the spindle, and then there is a sleeve you pull out with a stop. You fashion your own sleeve which has no stop (so the way through the subspindle collet is free) with the id slightly bigger than your part and you put it in place sticking out the back of the machine (you have to remove the cover just above the oil tray door). I dont know the exact technical terms of the pieces, but you may understand what I mean.. sorry.

So when it runs, turn it like you say and just feed it into the sub spindle to length, close the chuck, part it off, start program over and have the sub open its chuck just as the main starts feeding the new piece into it. Your pieces will drop out the end of the tube you fashioned and you can have them fall into a box (not much of a fall though! they should just drop in, youll figure out the best spot for the box, then all you do is maintain it).

That or you can find an extended piece attachment/option for whatever machine you are turning with.

[hacdlux]

[nomedia="http://www.youtube.com/watch?v=xCHRAcJRSPs"]YouTube- Citizen L20 - Long Shaft Demo[/nomedia]
a pretty good explanation of what all of us are trying to say

[Kennebec]

Thanks for the help people I have forwarded a lnk to the post to the gentleman who is trying to have this part made, he may have some questions.

Thanks again...
Kennebec