The Third Installment :
The next step is to hook a hose to the water swivel. I prefer to use a valve between the hose and the water swivel, despite the fact that the water swivel fixture itself has a valve. Since it is a brass fixture and valve, they can get pretty sticky and hard to turn. The rotation of the drill press will make the whole fixture and hose and everything else try to turn. The force doing this is not great but it still has to be mitigated and I find the best way is to simply use a piece of wire to hold the hose to the shaft of the drill press. Before we put the bit on. We should talk about a couple of issues. Run out or wobble, and the proper speed for drilling. Machinists measure the wobble of a drill bit that is in a drill press or other fixture with a machine and they call the amount of wobble the runout. Runout is a bit problem in most cases but for lapidary purposes the usual runout that we find is not a great problem. If the spindle of your drill press is worn or has been damaged wobble can be a problem and the hole that you are trying to make round would be elongated in one dimension. A major issue with core drilling is the speed of the machine. Most drill presses have variable speeds and I have never worried about the speed because I have always been quite conservative and used the drill press at the lowest speed that is available for core drilling. The particular bit that I am using in this tutorial was made by the company Smart Cut, a company which has excellent information about how to use your core drill safely and effectively. This bit is a 1 ¾” outside diameter bit and the Smart Cut speed chart says it is to be used at either 550 rpms or a speed that you find more comfortable. I have been using it at 250 rpms and feel quite comfortable using it at that speed.