Can you cut external Acme threads on mill using a rotary?

[RetiredRoger]

As in the title of this, can you cut external acme threads on a shaft using a rotary?  If so, would you use a surface toolpath or use a special tool?  Just doing some research here...

[RobertELee]

Certainly can. They're 29degree (if I remember correctly) walls. If it's a one-off I'd probably just surface using the appropriate sized endmill. Otherwise rough out with a standard end mill then use a 29degree tapered endmill to finish.

[RetiredRoger]

Thanks.  The shafts would be 21 inches long qty of 6.  I'm just doing some research for someone else, so I can answer their questions.

[Rstewart]

At that length, the diameter had better be beefy.  You're gonna need some kind of a support in the middle to have a chance, otherwise flex is gonna kill ya

[RetiredRoger]

At that length, the diameter had better be beefy.  You're gonna need some kind of a support in the middle to have a chance, otherwise flex is gonna kill ya

Yes sir.  They already had thoughts on using some kind of support.