I'm working on a project- building a recumbent trike. One of the steps that has me stumped is that I have to cut the 2" tubing so that it will mate up to another 2"tube at an angle. For right angle cuts, a hole saw works fine, but for shallow angles like 15 degrees, the hole saw will not make a good centered cut for me.

Basically, I need to cut a rounded hemisphere with a 2" diameter... I will need to clamp the tubing to the angle that I want cut out.

A vertical mill with a fly cutter will sort of work, if I clamp the tube to be cut at the angle that I want it cut, but it will only cut in the Z axis. This will not work on the shallower angles because those might well go beyond the length that I have available in my Z axis.

I suppose that I could buy a 2" ball cutter, assuming that I hit the lottery a few times :)

How should I cut this?

Most guys use something like this:
http://www.jointjigger.com/
Keep it simple, use a 2 inch hole saw, file finish the cuts for the weld prep.

regards

I have one and it works great... for 45-90 degrees. Unfortunately it won't do the shallower angles for me. Is there a simple way to do this with a CNC mill?

Hi:
Let's say you used a solids modeling program to create the "fishmouths" on the tube end. I'll state the obvious: if the cut is 90 degrees to the tube then plunging into the tube end with a hole saw or endmill is the ticket ( a circular profile on the top and bottom surface of the tube). For other angles, you basically end up with part ellipses on the top and bottom surface. So, by orienting the tube on a V block or a vise, A profile toolpath could be run non the top surface of the tube end, then the bottom, as long as the bigger cut is on the top (this allows the cutter to reach the lower cut).
If you had a rotary table or indexing fixture, then you could just cut the top profile, rotate 180 and cut the bottom profile. If you require fishmouths on both ends, and they have to be aligned, then you would fixture in such a way that you could flip the tube end for end, and then use a "finger" affixed to the table that the cut end of the tube could be butted into.
Let me know what you think.

regards