Light bulb cutting

[Tony Serviente]

I've got 3" diameter globe style light bulbs that I'm trying to take the base off of, leaving me a sphere with an inch hole. Have tried ring saw, band saw, and even gentle grozing with no luck. Glass is as thin as 14 thousandths. Anyone do this before?

[scooter riegelsperger]

Tony,
you might try scribing with a diamond scriber and then hit with a torch. I've cut microscope cover slips as thin as .005" thick with some success.

[Mark Kemp]

When I was a kid a had a book about cheap science experiments. They used lightbulbs for flasks. I can't remember for sure after all these years what they did (hmmm...wonder if I tied my shoes this morning...), but it was something along the line of what Tony mentioned. They may have scored the line, heated it, then dipped it in water up to the score. Or maybe it was the old wrap string soaked in a flammable around the bulb, light it, then immerse it.

[rosanna gusler]

so tony, whatcha gonna do with the globes? inquiring minds.........rosanna

[Rick Wilton]

If you have access to a sandblaster with pressure pot, it will work fine. Mask off with regular electrical tape and blast at a rather low pressure. 10-15 pounds. You'll be through it in no time, and have a clean edge.

[Tony Serviente]

Thanks all. Was going to try blasting, but my gun is awaiting a part, so it's down for a week more. I think that has the most likely chance for success. Might try the scribe and bottle cutting variant, but my intuition tells me that they won't do it. I'll report success if I get it. First reason for doing this is rather mundane. Someone brought in a christmas ornament that was their grandmothers, and the very thin globe had cracked. Internal decorations were fine, so my job is to recreate the ornament in a cost effective manner. Blowers could do it, but cost would be high. Diameter of old globe is almost exactly what the bulbs come in at. This is one of those jobs where you do it for the challenge and learning, and to make someone happy, cause I sure won't make anything on it. Now that I've been thinking about light bulbs for the past few days I'm interested in the idea of using them as forms for a kind of frit casting. Of course they'd slump on the way to fusing temps, and there would be a thin layer of non comp glass to consider, but the idea interests me, and I could imagine some interesting artistic possibilities.

[Brock]

How about a Dremel? Low torque should work. Brock

[frenchacidman]

I use my wet belt sander to open bulbs. Come in from the edge of the belt, make a notch to release the vaccum. Then rotate the bulb allowing the cutting edge of the belt to cut as it enters the bulb but not contact the bulb as it exits ( avoiding chips being blown out) This cuts easily and allows you to finish the cut nicely. On some bulbs you can twist off the metal base (breaking the glue bond) and then belt sand the glass directly. The finer the belt, the finer the finish. You can also open elitical holes in the head of the bulb using a #400 belt. Protect Your Eyes.
Pat

[Tony Serviente]

I like that idea Pat. Never deliberately used my belt sander as a cutting tool. I tried getting the bases off, but all were too solidly glued. I'm going to try a few bulbs tomorrow. Now I wish I had saved all those burned out bulbs I changed in the past year!

[Tami C]

Hi Tony, There is information in the old archives about lightbulb casting.
I did one quite a while ago, and it turned out kind of neat (but not good enough top make me want to repeat it.) Lightbulbs with no insignia are rumored to be 90 coe. Thats what I used, and its still holding down papers in my studio
Have fun experimenting!
TamiC