- Joined
- Feb 13, 2017
- Messages
- 2,138
It may be "off base" here, but way back I was given to understand that a center drill held in the tailstock against rotating work would "self center". This from an old timer in the plant machine shop who seemed to me to be on point. The theory I have held for many years is that the finished center cavity may be slightly oversized but true to the center of rotation. This is based on the rigidity of a short drill cutting to the side as the work rotates. With an oversized center hole, a center device will find and hold the center of rotation to get true work.
Sorry, I don't know the terminology for some of the points I'm trying to make. Hence there are too many "centers" here to make sense. Perhaps I don't have my caffeine level up to snuff yet. I don't do enough precision work to half, or less, thou to know if the thought is valid. At the level I usually work, it seems to pay off. The theory as explained to me makes sense and I don't worry about concentricity of my center drills. I will concede that most of my work involves small drills. My large size is only 1/4 inch / 6mm diameter for thr body. I have larger center drills but they are so seldom used that I don't consider them. Like the letter size drills, they aren't allowed to get rusty, but could easily do so.
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Sorry, I don't know the terminology for some of the points I'm trying to make. Hence there are too many "centers" here to make sense. Perhaps I don't have my caffeine level up to snuff yet. I don't do enough precision work to half, or less, thou to know if the thought is valid. At the level I usually work, it seems to pay off. The theory as explained to me makes sense and I don't worry about concentricity of my center drills. I will concede that most of my work involves small drills. My large size is only 1/4 inch / 6mm diameter for thr body. I have larger center drills but they are so seldom used that I don't consider them. Like the letter size drills, they aren't allowed to get rusty, but could easily do so.
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