best way to sand hemispherical depressions?

[Lee Alkureishi]

Hi all,

I have a workpiece that has a series of 4 hemispherical depressions ranging from 1/2to 1". They were created using core boxrouter bits in a drill press . Unfortunately, the low spd if the drill press created some bad tear out.

I know I won't be able to get rid of all the tear out without changing the shape, but does anyone have any suggestions for how best to sand/smooth this out?

Thanks in advance,

Lee

[Rick Lizek]

http://www.katools.com/shop/carbide-abrasive-sphere-burr-p-57.html

[Dan Hintz]

Man, that carbide ball would rip it a new one! You want a set of sanding balls, Lee. I can't suggest a specific set offhand, but they're sold plenty of places and in various sizes, so check around. They're similar to flap sanders, just in ball format rather than disc.

[Lee Alkureishi]

Thanks both for the tips - will check out the sanding balls :)

[glenn bradley]

I assume you don't have a plunge router or, you would have just used that(?). Something along this line could help: http://www.widgetsupply.com/category/dremel-grinding-stone-round.html The largest offered here is 1/2" but my dad has larger ones that came from a metal working supply. I'll try to find the name.

[Prashun Patel]

I'd get a foam backing pad for a ROS. You can get one @ 2sand.com (look under sanding accessories) but I'm sure there are others. This pad is about 1" thick and will conform to inside and outside surfaces. I've used them for post-carving shaping both convex and concave surfaces. Nice thing about this is that you can use different grits.

Caveat: center the pad perfectly and use at low speeds. Your ROS wasn't really designed to use something this deep, and you can get some vibration if not used properly.

[Lee Alkureishi]

Hi Glenn,

Thanks for that - I have a couple of those balls, but never considered using them on wood - I'll give it a try on some test pieces. And you are correct - I don't have a plunge router, so used the drill press instead. It's on my want list, but couldn't justify it right now for four holes... :)

Prashun, what size of foam backing pad do you mean? My largest depression is 1" diameter, and about 1/2" deep - not sure how a backing pad wound get into that cavity?

Thanks again