This is a guide on how to build a reasonably accurate jig for drilling a hole in a sphere with a hand drill. Following this step by step is very important to get successful results. There are basic measurement skills involved. The more accurate the measurement combined with the ability to match that measurement to the proper tool, the more successful your results will be. There is probably room for improvement to this technique.
Step 1: Parts & tool list
•bolts(2), washers(2 or 4) & nuts(2)
•hole saw or spade bit that corresponds to the size of the ball
Step 2: Determining measurements
I wanted to drill a hole in a 1" ball, so in this instructable all of my measurements will relate to that size. it is easy to adjust this jig for a sphere of a different size but once the jig is created it will only be accurate for the size of sphere it was created for. First, measure the size of sphere you would like to drill into, in this case 1". You want the middle layers to be roughly the same width as the diameter of the sphere. I used 1/2" plywood for my jig and 4 layers. In my example my ball is 1", so the two middle layers are 1/2" and they add up to 1".This technique can be done with as little as three layers or several if necessary. I wouldn't recommend using layers any narrower than 1/2" for the top and bottom layers. The top and bottom layers will be your drill guides, so, for accuracy's sake the thicker the better.
Cut your pieces to be the same size with sufficient amount of area around your ball. You want enough space to put two screws in each end and plenty of area around your sphere to be able to drill into it without compromising the strength of the jig. It will be easier to assemble if the pieces are cut the same size.