This is a heavy duty holsaw core rod. The handle on this is 7/16 and a 1/2 drill chuck is required. I have a 3/8 Chuck on my drill. I had to make dozens of 3 inch holes in our couch ( Also spell \"soffit \") For ventilation blinds. I put the handle flat with my bare hands so that the core stick can fit my drill bit. It works, but it shakes so hard. ( Pictures from Amazon. com. ) I decided to restore my core stick, but for the size of my drill chuck and center it won\'t shake. The first step is to build the handle again by welding. Wire feeding welding machine is easier to do this than Rod welding machine. ( I didn\'t take pictures when I actually did the project, so it was a remake. ) I need a way to put the core stick in the Chuck so I can rotate it in the center. The pilot is 1/4. I loosened the fixing screw that fixed it and inserted a 1/4 bar in its position. I put the 1/4 in my drill. The core rod now rotates on the drill bit in the center without any swing. Of course, you can\'t use holesaw on it like this. I hold the drill bit, so the core stick is in slight contact with the rotating grinds. Keeping it in contact with the grinding stone does not cause the drill bit to bump, but the grinding stone slowly and smoothly takes the high point, the handle of the core rod is round and in the center. Experiment with the speed of the drill bit to find the speed at which the drill bit is kept most smoothly. If there are low points and gaps, fill them with a little extra welding and grind again until round and center. I need a fixture to grind the plane on the handle. I started with two identical 3/8 plywood pieces. The diameter of the rod to replace the pilot bit is 1/4. I drilled a 1/4 hole in two plywood pieces. The hole is close to the edge of the plywood. I grind my calf 3/8 in diameter. I drilled a 1/4 hole from the last step to 3/8. As shown in the figure, install the core shaft on two plywood sheets. This simple stand parallel the core stick to the table top below. My grinding wheel is mounted on my radial arm saw. This means that I can slide my core stick fixture under the grinding wheel. This also means that I can reduce the grinding wheel step by step. I put the depth of the three apartments a little smaller than I thought, so the last \"cut\" might be light. This is to ensure that when heavy cutting is carried out on the previous plane, part of the wear of the grinding wheel does not affect the final cutting to any extent. The hex nut on the core provides a convenient guide for rotating the core rod 120 degrees between the three planes. In order to grind, I simply slide the core shaft and its support horizontally into the grinding wheel. Here you can see the handle of the core stick after I finish grinding. The three apartments are equal. The circular part of the handle is located in the center of the core shaft. The core stick no longer shakes in my drill plate. Yes, it has a slight decrease in diameter and strength, but if I don\'t force when using holesaw in the future, that\'s fine. I did a precision job without the need for a normal machine tool. Most people who see a in operation for the first time are amazed at how well the trimmer machine online is managed. Get cost effective and professional automated cnc machine advice for your solution at Kingtool Aluminium Machinery. Kingtool Aluminum Doors and Windows Machinery Co., Ltd. expert is your first choice! Our company is professional in selling cnc machining center as well as providing a series of relevant services. Your co-workers, investors and clients have busy schedules, and it can be hard to get everyone in the same place at the same time for Copy router. So, it is important to create a connection between company and clients. Latest technology and manufacturing equipment has improved the quality of curtain system.