• When cutting a keyway, instead of indicating to center, I touch the cutter off the part, slightly raise the machine table and make a cut into the part about 0.125 in. beyond the cutter centerline, then back the table down and stop the spindle. With my index finger, I feel the cut I just made. If the tool is off center, one side of the cut will feel deeper than the other. I adjust the cutter until both cut sides feel the same, which centers the tool.
• I use an edgefinder when trying to locate center on round workpieces that are too big for swinging an indicator. Start at about a 9 o’clock location on the part, find that edge and move to center. Then move the edgefinder in the Y axis to a 6 o’clock position and, without moving in the X axis, find that edge and move back to center. Repeat the process about 3 or 4 times, and you’ll be on center.
• To set a lathe tool to center, lightly clamp a 6-in. scale between the tool and the workpiece. If the tool is above center, the scale will be pitched away from you when looking toward the machine’s chuck. If the tool is below center, the scale will be pitched toward you, and it will be vertical if the tool is centered.
• While using an indicator is best, I have two quick methods for centering a workpiece in a lathe chuck. The first is for workpieces with centers in their ends. I snug the part in the chuck and move a live center mounted in the machine’s tailstock into the workpiece end center while the part is spinning. Let the live center push the workpiece into the chuck about 0.125 in., stop the lathe and fully tighten the chuck.
For the second method, I use the flat end of a piece of material that is softer than the workpiece. A toolholder or piece of aluminum works well. With this piece of soft material clamped in the machine’s cross slide, I snug the workpiece in the chuck, rotate the machine spindle at about 250 rpm and move the piece of material in until it lightly touches the workpiece. I switch off the machine and fully tighten the chuck.
• I roughly locate the centers of large part diameters on a vertical mill by mounting a dowel pin in a drill chuck or collet holder, then lower the pin nearly to the uppermost surface of the part diameter. I measure the distance from side to side and front to back using a scale and adjust the respective axes until the measurements are equal.
Adding more pieces to a coolant lock-line can be a pain. What I do is microwave a cup of water to boiling and place my lock-line sections in the water for about a minute. This softens them, and they easily pop on to add to a coolant line.
Shop’s latest CD
I needed to turn a 0.300- in-thick workpiece on a lathe, and obviously, my cutter came dangerously close to hitting the chuck jaws. So, I cut a used CD to fit in the chuck and shim the workpiece out a bit. CDs are held to good tolerances, are easy to cut to needed size, and have a hole in their middles for parts with through holes.