- Joined
- Feb 13, 2017
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- 2,138
I was watching a video on https://www.homemadetools.net/ regarding a "loose" Logan. The size and the brand have no real bearing on the question. I was taught many years ago by a ("lifer" military) machinist. I didn't have the craft knowledge to learn all that much from him. But what I did learn has stayed with me for 50 years. From his teaching, there is a shoulder at the end of the spindle. This shoulder is the registration surface for the chuck. The threads are merely to hold the chuck against this surface. They have little bearing on alignment. My tutor emphasized the point about never allowing chips or dirt when I was mounting a chuck, for this reason.
I have seen examples of users having a gap at the back of the chuck. It seems to me to be a "too shallow" chuck mounted on extended threads. That is the most likely answer, to me, there may be another. The chuck bottoming out on the threads before closing with the shoulder. The problem was usually presented as "loose bearings" in a friction bearing machine or a misaligned chuck. In this video, the operator had a video camera pointed at the back plate where I saw movement. Thus the question. . .
I have swapped chucks around between an Atlas (Craftsman) and a Taiwanese 9x20 having the same (1-1/2-8) thread on the spindle. The Chinese machine (Grizzly 1550) has a longer spindle than the Atlas. It was necessary to make a "shim" plate, ~1/2", to make up the difference. It seems to have worked properly, both chucks run reasonably true(as in < 0.002) on both lathes.
The question is: Is this a valid perspective or was I lucky when I made the "shim"? All responses are welcome, the older professionals more so.
I have seen examples of users having a gap at the back of the chuck. It seems to me to be a "too shallow" chuck mounted on extended threads. That is the most likely answer, to me, there may be another. The chuck bottoming out on the threads before closing with the shoulder. The problem was usually presented as "loose bearings" in a friction bearing machine or a misaligned chuck. In this video, the operator had a video camera pointed at the back plate where I saw movement. Thus the question. . .
I have swapped chucks around between an Atlas (Craftsman) and a Taiwanese 9x20 having the same (1-1/2-8) thread on the spindle. The Chinese machine (Grizzly 1550) has a longer spindle than the Atlas. It was necessary to make a "shim" plate, ~1/2", to make up the difference. It seems to have worked properly, both chucks run reasonably true(as in < 0.002) on both lathes.
The question is: Is this a valid perspective or was I lucky when I made the "shim"? All responses are welcome, the older professionals more so.
Bill Hudson