Tailstock trouble.

ranch23

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Posting this here because I do gun work on my lathe. Am trying other ways to chamber, do it through the headstock now, and was aligning my tailstock. While I was at it decided to tear it apart and clean it up. American Turnmaster 13 X 40, 2 speed motor, Aloris toolpost, 2 axis Mitutoyo DRO. After reassembling it, much easier to adjust, laterally was a snap, heighth is .002 too high. Believe I will put it on the surface grinder and take 2 off. By the way I use a Torque wrench to torque the hold down bolt so that it is repeatable. It always turned a slight taper between centers, which is part of the reason I chamber through the headstock, with an outboard spider. Have a dial indicator rigged up on the tailstock quill for depth and believe I will make a plate to span across the bed and put an indicator on it to bring the tailstock back in position. Maybe just a stop. Any thoughts?
 
You don't need a plate. Rig up an indicator mount that looks like a lathe tool so you can mount it in your tool holder. In the attached pic I'm using two DI's because I'm checking my headstock alignment. What I did to true up my tailstock was to turn a 1.5 inch piece on centers while adjusting the tailstock until the piece had no taper. Then I saved that piece so I can restore alignment going forward by just putting it on centers and sweeping a QCTP mounted DI across it by running the carriage back and forth.

TOOL POST INDICATOR HOLDER.JPG
 
I'd go with epanzella's comments (post #2). I'm thinking that if you elect to grind off "2" to lower the tailstock axis, you'd find that it makes a very little difference in eliminating that taper; the work is machined on its side (9 o'clock), not on its top (12 o'clock). Hope that helps.
 
But doesn't the tailstock being higher or lower still cut a taper?
 
Yes, but only by an indetectable amount. When turning a .5" shaft with a .001" vertical offset you'd see an error of approximately 4 millionths of an inch if I've done the math correctly. Of course the error increases rapidly with the offset.
 
Leave the tailstock alone. They are often made .002" too high to compensate for wear that will happen in use from sliding it. You don't want your tailstock becoming too low later on. As said,the stock is cut on the side,so any taper is miniscule if your turning tool is properly set on center of the side of your stock.
 
If you push the reamer with a dead center, then you need to get the tail stock down, because it will have the same effect chambering a barrel as a tail stock being off front to back. Check the bottom of the base section where it rides in the ways. My first lathe was quite rough. A few strokes with a flat file took down the high spots and all was well. I'm not a floating holder person, there is no rigidity that way, but many use them and don't worry a wit about a few tho' off in a tail stock.

I use the carriage itself as a stop for the tail stock. If you can't find a place on the carriage that positively contacts the tail stock when they meet together, then JB Weld a pice of stock that will act as a contact point. Once you start chambering, lock the carriage down, and your tail stock will return exactly each time when you pull the reamer out to clean. The dial on my tail stock quill is graduated .001", so I have no trouble advancing the reamer to the right depth.

If you want a different way to hold the reamer, send me a PM.
 
I was taught bout every lathe will not be centered height wise. If it bothers you I bet a .001 shim under the rear would nod it down. As was mentioned, the error is so small you would likely never see it in the work
 
You don't want to "nod it down", because the quill will not travel parallel to the bed when advancing the reamer.
 
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