After the last blog it is a logical step to continue this month by discussing coring – after-all, a core is just a larger hole. But the technique for coring is quite different. I should say techniques, since there is more than one way to cut a core.
The first one I’ll mention is the ultrasonic corer, used to cut long, straight, small holes in beads, etc. The “drills” are often hollow and diamond-tipped so they are technically core bits. I know little about this technique unfortunately though I’m sure I could find a use for it in my workshop! I don’t think it is used by many jade carvers, but who knows, maybe one of them won the lottery?
The second method I have used successfully however. It employs beautifully engineered core barrels (see Picture 1 below) which have an internal supply of water to cool the work, lubricate the process and clear the rock flour, delivered through an external water supply hose and a slip ring (collar) which fits over the stem/shaft - water flows to the inside of the barrel through a hole in the stem. Because the water is under pressure from the tap (or overhead reservoir) you can end up with a certain amount of water spray and have to restrain the water feed pipe from turning with the core barrel. The advantage is that these are well engineered tools and you can use them in cutting longer cores. With this method you can reduce the rate of “pumping” the core barrel (see last month’s blog by Steve) because the water pressure cleans and cools things for you to an extent, at least with small jobs.
The third method is a variation on the second. I recently bought a couple of C-Cut Diamond Coated Hole Saw’s (See Picture 2 below), though there are many companies which make them. They are very affordable, and will last a while if you treat them carefully. They range from 6 - 100+ mm diameter – quite a choice! I found using them straightforward, simple, clean and easy. So I’ll describe this method:
If you are planning on using a large diameter core barrel, or need to core through a thick section of rock you would need to check the recommended rpm and maybe buy the second type of core barrel I described above. And clamping the piece becomes important, rather than just holding the block of wood. But start small and build up!
On this page I intend to add monthly updates on aspects of jade carving. I also plan to invite more experienced carvers to offer a "master-class" on a particular subject of their choice. With this I hope to enthuse both the novice and the expert in this ancient and beautiful art-form/craft. And comments are welcome!