Q: How to cut holes in a sphere?

[Weezer]

Hi there,

I was wondering if there's a proper technique to cutting holes into plastic spheres? I was going to use a forstner bit in a drill press, but I'm not sure if that will make accurate holes... or be safe.

I only have one set of plastic spheres so I don't want to mess them up.

Thanks.

 

[Charles Kline]

You could make a plywood box for it to sit in so it wont roll around then use the forstner bit and the drill press.

Or make a holder like this:

Or:

The second one might not work in your situation.

 

[JFB64]

I used a plastic funnel as a guide to drill a series of holes in a sphere once. I inserted some brass tube in the stem of the funnel to act as a bushing for a twist bit and to make up for the difference in diameters. Put the bit in the drill press, then slide the funnel over the bit, then place the sphere under the funnel. The cone of the funnel will center itself on the sphere allowing the drill bit to bore perpendicular into the sphere. You'll also need to cradle the sphere somehow. I hope this helps.

 

[Sluis Van Shipyards]

Depending on how thick the walls are, I usually use this bit with my Dremel flexshaft. You just use a circle template to place a circle where you want it, then drill a pilot hole with a drill bit, then use this to open up the hole.

 

[Compressor Man]

I would think that a hole saw would be a good way of doing this.

Chris

 

[TheAdama]

Hole saws have a pretty limited cutting depth. A spade bit might work better. Are the sphere's solid or hollow?

 

[Wesman]

Well, you don't say much about the scale of things. Drill bits designed for plastics/acrylics are the most accurate for smaller holes. Hole saws don't come in really small sizes, but would be the tool to use (at slow speed) for larger holes. I would still use an acrylic bit to make the center hole for the hole saw. There will be clean up of edges, however. The jig to hold the spheres look good, although I am more basic, using a board with a hole in it centered on the drill press into which one would place the sphere, being then held as gently as possible with a padded jorgensen clamp which is itself clamped to the table. I would not use a forstner bit on plastic, as a normal thing, nor would I use a spade bit. The dynamics of the two I did recommend are much friendlier to plastic. You could also use a little WD-40 on the bits to ease the cutting.