I drilled a 1/2" hole down the center and used a small spindle gouge to remove as much material as I could reach. It kind of worked. I couldn't get to a lot of material just inside the opening with the end of the straight tool. So I picked up a 5/16" steel rod stock and some brazing rods at the orange borg a couple of days ago, and made a hollowing tool for under $10.
I bent the last few inches of the rod about 20 degrees in a vise. Then I got an old 3/16" drill bit ("black oxide" no mention of the alloy used) and ground a flat on both the steel rod and the drill bit so they would mate together. I wrapped a bit of thin steel wire around the assembly to hold it while I brazed them together, which I did with a common propane torch. I've never brazed before, but it's pretty much the same as soldering, which I've done plenty of. I didn't use any flux paste, just the stuff that was on the outside of the rod.
I cut the drill bit off about 1/2" long, shaped the tip into a scraper, and did some general cleanup on the grinder. Then I turned a quick handle out of a scrap of alder and a 1/2" copper plumbing coupler, and epoxied it all together. I gave it a very quick test-drive, and it seems to work well enough for my purposes.
|Quick-n-dirty Home Made Hollower|
|Failed Braze Joint|
Update: I put it to the test tonight, and it started working well, but the braze failed and the cutting tip fell off after a few minutes. I can see that the brazing alloy only stuck to a very small part of the joint, which I think is due to the tiny amount of flux used. Basically, whatever melted off the rod when I was heating the joint is all there was. I'll get a can of paste flux and try again.
|Brazing is pretty easy (2nd time around)|
|Hollowed Globe for a Christmas Tree Ornament, ~2" dia.|