[MarcusWolschon]

What is the best/common way of mounting a cylinder of carving wax to a 4th (horizontal rotating) axis for milling?

Are there special chucks used or some common material to make cores to grip with the jaws?

[Tom-AMS]

depending on how much cutting force you plan to apply, tall pie jaws on a 3 jaw scroll chuck, bored to fit the cylinder, may be quick and easy solution.
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[MarcusWolschon]

The wax is way too soft to be held by 3 jaws. It neraly breaks free under it's own weight doing that.
We're talking 1-2 Kg of carving wax mounted horizontal.

[awerby]

You can screw a block of wood or something to the bottom of the wax cylinder, and grip that with a 4-jaw chuck. Of course, you still have to support the other end, by using a drill-countersink to put a divot in the center and running the dead-center of your tailstock into it.

[Tom-AMS]

We chuck 4 dia " x 4.5" long wax cylinders in a 4-axis when we're prototyping piston crown shapes & skirts. We use Pie Jaws on a 3 jaw chuck, bored so the cylinder sits 1" deep and is gripped horizontally, approx full 360° by the Pie Jaws, and have ZERO problems with the cyl breaking off. The 360° support from the Pie Jaws evenly supports the weight of the wax and distributes/limits the bending moment so it does not break free. Note: Machinist wax is available in different hardness/strengths; maybe you could try a stiffer / harder wax? Or run a center support on the opposite end? We also prototype air-cooled engine cylinder jugs from longer and larger diameter wax cylinders ( 8" diameter x 10" long). To support them we bore the center and press a cast iron sleeve (a common $20 part sold to repair engine blocks) thru the length of the wax cyl. Then we use Standard Jaws on a 3 jaw chuck to grip the ID of the sleeve. Perhaps you could adapt a similar solution, by pressing a steel shaft thru ( or partially thru) the wax cyl.?

[MarcusWolschon]

I'm currentl using an aluminium profile as a core.
A round block of wood didn't work because the surface was too smooth and the wax detached from it.

I'm asking for common, tried and true ways to do this.
Carving wax is a common prototyping material. So there must be some best practices.

[MarcusWolschon]

We use Pie Jaws on a 3 jaw chuck, bored so the cylinder sits 1" deep and is gripped horizontally, approx full 360° by the Pie Jaws, and have ZERO problems with the cyl breaking off. Or run a center support on the opposite end? We also prototype air-cooled engine cylinder jugs from longer and larger diameter wax cylinders ( 8" diameter x 10" long). To support them we bore the center and press a cast iron sleeve (a common $20 part sold to repair engine blocks) thru the length of the wax cyl. Then we use Standard Jaws on a 3 jaw chuck to grip the ID of the sleeve. Perhaps you could adapt a similar solution, by pressing a steel shaft thru ( or partially thru) the wax cyl.?

I didn't know pie jaws existed.
That sounds like a great way to do it.
I'm currently running a tailstock from the other end for the roughing but have to remove that for the last part of the finishing since the designs all have a tip.
I thought about making a bezel (Germen: Lünette) but am fearing to create marks on the part surface (they are masters for casting and thus need a perfect surface finish).
Running an aluminium profile with large undercuts as a core seems to work somewhat. The leverage of a small core against a large diameter cyliner at the chuck-end limits speeds to a crawl.
I'm using the the green Ferris one (55 Shore D). Only the gold and orange ones are harder but they are nearly impossible to get.
(Getting the green one in Europe is already a challange)