thanks for all your help
oops link got truncated
http://www.usplastic.com/catalog/pro...oduct_id=11248
4/5" acrylic tube with a 1/8" wall. Thanks for that infor blue that is helpful. Will a fly cutter work on a sphere though? I thought about that, and I'm sure my shop has one but don't fly cutters have to be perpendicular to the surface.
that sounds like an interesting strategy as well billbartuska. In total I believe I'll be cutting 4-6 holes in 3 sizes, the smaller sizes will be tangent to the surface so this seems like a good way to mark up those holes. I'm dense as the tube only needs to be mounted to the "inside" of the sphere so hole diameter shoudln't be as exacting. I.e I'll be mounting a tube over a hole, not trying to fit it IN the whole and flush to the surface.
any clue as to the where to purchase weld-on acrylic glues?