As you may have guessed from this post, I spent another Saturday cutting the bottom(s) off of glass sphere(s). Yes, plural. I broke my replacement sphere before I was a quarter of the way around. This was due to one of the following reasons: 1) I had placed packing tape over the blade path, hoping to reinforce the glass. or 2) my tile saw blade holding bolt had loosened. Regardless, I cracked the sphere quite well.
So, I moved on to my backup replacement sphere (number 3 for those of you keeping track at home). I had already figured out that sharpie ink will NOT stick to glass when sprayed with water from a tile-saw, so I continued to use masking tape to mark where my cut should be on sphere number 3. I also placed packing tape on the non-cut side of the masking tape, as I was impressed with how well it had contained the breakage from sphere 2. (I plan on using packing tape to cover a large portion of the inside of the sphere (except the viewport) as a poor-man’s tempered glass substitute. )
I was able to cut this (third) sphere almost completely successfully. The only issue was when I was making the last cut to complete the circle. When the blade got very close to completing the circle, the small amount of glass shattered (breaking off the circle of glass) and started a 3″ crack, which looked very much like the first crack on my first sphere.
The technique I found worked best is to push the glass sphere towards the blade (as opposed to rotating it in place over the blade). When you get to the end of the cut, you have to pull the sphere back out, then turn it a bit (and rotate) to adjust for the next straight cut. Because I don’t have a work table, my tile-saw is sitting on my back porch, and I have to crouch down to cut the sphere. I typically make around 4-5 cuts (approximately 1/3 of the way around the circle) and then take a 10 minute break to make sure I don’t get impatient or tired and rush things. The whole procedure (with breaks) took around 45 minutes.
After rinsing out the glass shards and dust (I did mention that you should wear full goggles, gloves, and a face mask when cutting glass, right?) I dried the sphere and then immediately used one and a half tubes of epoxy putty to make a bead of epoxy around the edge. This will hopefully serve three purposes. First, it covers up any sharp edges on the glass. Second, it will hopefully provide some strength to the open rim. And finally, it allows me to mount two small (but strong) magnets on either side of the sphere, (one for each shoulder). I’m counting on gravity and a bit of friction to do most of the sphere holding work, but the magnets will hopefully keep things aligned and steady.
Eventually, I will probably try and cut my fourth sphere, learning from the 3 inch crack in this one. My plan is to cut about a half of the sphere, then cover my cuts with packing tape. After that, I will make one cut at a time (connecting to the last cut) and cover the gap with packing tape. The goal is for the packing tape to support the two pieces of glass (sphere, and cut-out circle) well enough so that when I make the final cut, the blade will grind through to complete the circle without cracking the glass. However, for now the slightly cracked sphere is my working version. I figure if I break it while mounting it to the cowboy collar I’ll have one sphere left, and if I don’t, I’ll have a backup sphere for the costume.