So a 6" 4-jaws independent chuck will be the way to go? The difference in price (for the ones I am looking at) is 40.00 more for the 6" over the 5"...
Too bad those 4-jaws combination chucks are so expensive... one of those would have been nice... focus, man! focus!! You have another lathe coming...
Yes, do focus. What did you order with the PM lathe? If you didn't get a 4J with the PM, then the one you get now, could be used on the PM. If you just need to practice some and budget is tight, you know your answer. If things are really tight, just use the 3J. A 4J isn't worth marital disharmony. It's ok to pause the binge. You can learn a lot with a lowly 3J. When you can shake the money tree and $$ falls off, then buy the 4J.
A 6" should do fine. A 7" would push the limits of a 9" machine. The 6" chuck will close on work as large as 8". If you are going to work on stuff that big, the 9" machine is
much too small. As would be the PM machine that you have coming. With something that large you would need to watch that the open jaws extending outside the chuck body did not reach the shears. Remember, swing is diameter. Center is only 4-1/2 inches above the shears. A 6" chuck takes up 3" of that before opening the jaws. Even with small work, it is a good practice to pull the chuck through at least one revolution by hand before starting. It will soon become a habit, a
good habit that will pay off when you least expect it.
Dream big,
but keep those dreams under control. A 4 jaw chuck is a heavy device. Even the front bearings on a 12 inch machine would be loaded heavily with one mounted. I neglected to mention, my 5" 4 jaw chuck is a scroll chuck. It is self centering, useful for square and octagonal work. I do most of my work on models, my 4 jaw independant for modeling is a 75mm chuck, roughly 3 inches.
I do have a 12 inch machine, an Atlas Craftsman, and an 8" 4 jaw independant for it. But even with a 12 inch swing, it's all I can do to lift the chuck into place. An old man needs to keep an eye on his physical limits. I shudder to think what the front bearings carry when work is loaded and I make a cut. Never mind large diameter work, even a crankshaft at 3/4" diameter with journal offset around 1/2" would be a "hand full" for a 12 inch lathe.
I stand on my call earlier to keep the 4 jaw chuck at the top of a wish list. It isn't necessary at this point in your learning curve. As you gain experience and you find a
need for one, you can negotiate with SWMBO about it. She might possibly see to it that one shows up as a gift one day. It
has happened, though not to me. Yeah, well. . .
To digress into a
different subject, tail stock centers: There is today a "live center" that runs on ball bearings. Going with "
old school" definitions and the old books I learned from, the difference between a "live" center and a "dead" center was that a dead center was hardened and a live center was not. Such a "dead" center would be used in the tail stock where work would rotate on the center. And the "live" center at the head stock where it could be trued as necessary. This is no longer an absolute but watching out for hardened centers is an issue. If I were to use a "non rotating" center in the tail stock, it would need to be hardened.
When the concept of a "ball bearing" center came along, the defination slowly started changing. Confused yet? On the current crop of machines, the head stock is MT3 and the tail stock is MT2. So it's not too big an issue. This includes my Atlas 12X36, build somewhere around 1951.
BUT, I have an adapter in the MT3 headstock for my own purposes, making it MT2. Same as the tail stock. It would be very easy to confuse hardened and non-hardened centers. This comes about from an Atlas benchtop horizontal milling machine, which also has an MT2 receiver at the quill.
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