best bits for smooth 3D milling

[jkaras]

Hello-

I have a Shopbot PRS Alpha with a spindle head attachment. I was wondering if it is better to use a flat end or a ball end mill to route a curved 3D object. My object is a concave curved trough. I want to do minimal if any sanding to achieve a perfectly smooth surface. This is my first time making a 3D object with it. Any guidance is appreciated, thank you!

-JK

[dana_swift]

I use a ball nose with a small step over for situations like that.

The radius of the ball nose is determined by the curvature of the surface I am carving. A light sanding is still required, for my work it takes about 5 minutes. That removes any remaining tool marks.

D

[bleeth]

You didn't mention the size of the trough. If it is like the cove shape on some moldings it can be done with a larger ballnose in one pass. I just had a curved arch molding and pulled off the cove with a 1 1/4" Diameter roundnose bit .30 deep in one pass in poplar. Minimal sanding and a minute to cut.

[Brady Watson]

...I want to do minimal if any sanding to achieve a perfectly smooth surface...

Use a ball end mill & drop your stepover down to 8%. Use common sense when choosing diameter. Machine slowly.

-B