Introduction: The Sphere Center Align and Drill-O-Nator
When do you need a [Blank]? That is the question. The second time my pants fell down in public was when I decided it was time to get a belt. The second time I tired to make grilled cheese directly on the stove top was when I decided it was time to purchase a pan. The second time my former roommate caught me using His toothbrush was when I decided it was time to start locking the bathroom door. Ever hear of privacy? Jeez!!
This leads me to Today's topic .. When to make a shop jig/gauge/tool? For me, the answer is simple. When I need to achieve the same goal more than twice, it's worth my time to make the jig.
Step 1: Some Options
A few months ago I made some helmet display stands and I needed to drill a hole in some wooden spheres to accept a dowel. Naturally, I wanted these holes to be centered. Have you ever tried drilling a centered hole in a sphere freehand? Maybe you can do it, but I'd have better luck teaching my cat to order take out in perfect German. He probably doesn't even know the address because he's too afraid to go outside ... I guess he could've seen it on the incoming mail though. I'm getting off task.
The quick solution is to drill a hole in a board, which is smaller than the sphere. then put the sphere in the hole and drill away. As long as you didn't move the afore mentioned board, you should be good to go. This is what I did with the Helmet stands ... then who knows what happened to that board. Probably a sacrificial board for the drill press or tablesaw ... then onto the firepit.
It's time to make a jig/gauge/thingy.
Step 2: The Parts
I made my jig out of 3/4" plywood and 3/16" hardboard per usual. I didn't need the hardboard, but the plywood I used was pretty rough and I like hardboard. For tools, I used forstner bits, glue, brad nailer, and some marking gauges.
The width of my jig is 6" so my first step was to rip a length of plywood to the dimension. I then cut that into separate parts - 24", 6", 2", and 1". I cut the hardboard to 6"x6".
Step 3: Fabrication
I want my jig to attach to my drill press table quick and easy. I came up with a solution that works for me.
On one end, I made a "hook by laminating 3 layers of plywood. Since my drill press table is 3/4", it fits perfectly.
Once that was in place, I placed it on the drill press table to find the middle of the jig in relation to the table, which was 11". Since my sphere base is 6"x6", I measured 3" to the left and right of this center mark. Within this location, I laminated a layer of plywood and the hardboard using glue and brad nails.
Step 4: Layout Lines
Using some shop made marking gauges (Instructables for both), I laid out the hole for hanging the jig, as well as the center of the sphere base.
Step 5: Drilling the Sphere Base
Start with the largest bit and work your way down. My largest forstner bit is 2" so that is my starting point. I drilled through the hardboard and a single ply of the plywood. Then I switched to the next smaller bit and drilled two more plys ... repeat until your heart is content. I personally did 2", 1 3/4", 1 1/2, 1 1/4" and 1".
Step 6: The Function
Use the jig itself to align the drill bit with the center. Then clamp it in place and put the sphere in position. The picture above is a 1 1/4" wooden ball. The first image/thumbnail is a 3" styrofoam ball.
It could be made with just one sized hole, but I wanted more flexibility. I could be made much simpler than this, but I wanted to be able to clamp it down and not worry about alignment for consistency.
Step 7: Glamour Shots
Here are a few wider shots so you can see the construction and how it integrates with my drill press table.
Admittedly, this is a jig for a limited audience, but it's useful to me. In fact, it's first job is assisting with drilling holes in superballs so that they can become mallets for a tongue drum.