Heavy taper, help with velocity stack how to.

[GunsOfNavarone]

One of the reasons I bought this lathe, and the tooling, expensive block of aluminum and well, let's just say I spent $2500 so far to make a $50 set of velocity stacks. Its about the adventure! Anyway, the picture attached is ballpark what i want to do. How do you pull off that taper? Would tailstock offset be able to do that over such a short distance? These are about 2.5" long. ..and this part may be more challenging, but I would LIKE to have a "fin" around the inside leading around and funneling down to small end (to aid in causing a vortex sort of wind pattern.)
Thanks for the input!

 

[JimDawson]

I think for those you will have to use the compound and hand feed it. The tailstock offset would not do it.

 

[pacifica]

As long as your taper doesn't exceed the travel of your lathe compound, I would use the compound.
For extreme accuracy of the taper(minute of angle tolerance)use a sine bar setup w. compound.

 

[GunsOfNavarone]

I wouldn't even know where/how a sine bar would be used on a lathe, being that the cutting tool is somewhat static in the tool post.I
Hand feeding it once would be very difficult, but being th at it would take MANY passes, seems impossible. People do this? No? Is it CNC LATHE possible only?

 

[off center]

Very easy to do with a compound. . PM me after six o'clock. And I will walk you through it.

 

[Bob Korves]

Stacks like those are usually spun from straight tubing, and then fitted to a connector piece.

 

[RJSakowski]

I wouldn't even know where/how a sine bar would be used on a lathe, being that the cutting tool is somewhat static in the tool post.I
Hand feeding it once would be very difficult, but being th at it would take MANY passes, seems impossible. People do this? No? Is it CNC LATHE possible only?

Tom Lipton, Ox Tools, did a nice You Tube video on setting up a compound to cut a taper using a sine bar.

 

[JimDawson]

Hand feeding it once would be very difficult, but being th at it would take MANY passes, seems impossible. People do this? No? Is it CNC LATHE possible only?

Yes, people do this Very easy, and yes many passes. No CNC required. Even possible to make tapers longer that the travel of the compound.

 

[Tony Wells]

You don't have to do the whole thing with the compound. Plot out your -X- and -Z- cords and rough it out in steps, leaving just enough to finish with a minimum number of compound passes. Do it in two ops. Rough them all, then setup your compound. If your compound has a dial retention nut, consider a speed-handle or something to lessen the difficulty and tedium of plain hand cranking.

 

[jdedmon91]

I wouldn't even know where/how a sine bar would be used on a lathe, being that the cutting tool is somewhat static in the tool post.I
Hand feeding it once would be very difficult, but being th at it would take MANY passes, seems impossible. People do this? No? Is it CNC LATHE possible only?

It is you just have to plan it out. CNC spoils a lot of people because of the capabilities of them. The way I’d do it is to rough out the parts by turning off the majority of the material then cutting the tapers last. Still with a large block of aluminum this will take a while


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