Rotary Axis Questions

Hi All,

I’ve had an Avid Pro 4896 for the last four years and have done all sorts of things on it. Part of my business is replicating historic spindles for porches and staircases, which I do by eye on a lathe from the 1950s. At this point in my life I’m not so interested in turning dozens of spindles at a time, so I’m considering getting a rotary axis. If anyone has opinions or experience on the following, I’d be grateful:

  1. How fast (feeds, speeds, and depth of cut) are practical for this sort of job?

  2. On a lathe, skinny spindles often need support in the middle to stop whipping and the resultant chatter. Is that a consideration here? By skinny I mean sections down to say 3/4" with most of the spindle much thicker. I’m not considering making chopsticks!


I bet you could do it in a reasonable time. A rotary spins way slower than a lathe so whipping won’t be an issue. Do you have some pictures of the types of things you’d want to make on it you could share?

I think the speeds and feeds that are practical are basically the same as flat machining in X and Y., i.e. they are related to the bit, material, and depth of cut. There really isn’t a machine limitation specific to rotary machining. The one exception, which is related to your second item is if you are cutting long thin pieces, then you may have to ease up on your feedrate and/or DOC when trying to minimize the deflection.

Its a nice tool for replicating spindles. If you can draw the edge profile accurately, it is easy to wrap it (in either F360 or Vectric) to make the spindle.

Thanks for the replies. Here is a typical batch of stair spindles that I turned a few years ago. Some are square on both ends, and some are not but they are mostly Victorian era designs. I’ve also done runs of porch spindles, but they are generally shorter and of a larger diameter so they will behave just fine.

Also, I do all my 3D CAD in Rhino 3D, so drawing the edge profile and then revolving it into a 3D object to import into VCarve Pro (I don’t have Aspire) is no problem. I do all my 3D carving jobs that way and, in tests, VCarve Pro works fine for rotary jobs as well.

As long as there are no undercuts you can replicate the lathe. A lot of my wood lathe friends will slightly undercut to get a visually well defined step or division (whatever it’s called, parting line?) and those will be missing.

Another thing is the end mill has a diameter whereas the lathe tool can have a point (or the angle of the tool can be such that it is effectively a point) so you can lose those crisp lines. You can replicate it by switching between flat and ball nosed end mills with either careful manual tool changes or an ATC. But that can be tedious.

I use to use Rhino and the 3rd party g-code generator RhinoCAM. When Fusion 360 came out I never looked back.

I’ve been messing with some continuous 4th axis work lately:

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You’re really right about the sharp cuts that are present in many spindles. However, if the rotary axis got me 95% of the way there I could put the almost finished spindle on the lathe and finish the cuts with the skew chisel. And spindles are easy to sand on the lathe.

I looked at RhinoCAM but it was out of my budget. I’ve been using Rhino for a long time so I’m not sure that I’d want to change to Fusion360 at this point. Although it looks like it has many strong points.

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Oh! Don’t get me started. Rhino has lasted as long as it has because of its interface and ease of use. There are few 3D applications that elegant.

Trouble is there is a difference between modeling and CAD. Rhino is missing key features like assemblies, motion studies, analysis, simulations, CAM… blah, blah, blah.

I couldn’t live without all the other parts. I see my copy of Rhino every so often it it brings back fond memories. But that is all it brings these days.

I get that. I have a good friend who needs all of the extras and his company has the money for Solid Works. As for me, I design and build custom furniture out of wood, do turnings, and replicate historic moldings on the CNC. So for me Rhino is perfect and for the CAM I just port drawings over to Vectric.

Solidworks is $49.50 to all members of EAA.

Ugh, nothing free lasts forever. It use to be free :disappointed:

I had no idea. That’s neat. I’m not a pilot, and if I joined EAA I might be tempted to build an airplane… My wife is very supportive, but she would likely draw the line at that. I’d better stick with boats. :grinning:


The trick is take out your map and draw a circle around your house with a radius of 740 miles. Then show it to the wife and say, “here is the limit for our weekends, pick a place to visit and weather permitting… we will go!”


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