Tailstock pressure

[curtis cutter]

How does one tell when there is the correct pressure on the live center?

If I were to put an inch/pound torque wrench on the tailstock handle nut, what would be the correct torque value? Then I could get a "feel" for the setting of say a 1" diameter work piece.

[BadDog]

I've never worried about specific torque, and with different tail stocks and different screws, I don't think there is a value that can be put on it. But basically, you just want it in good contact. Unless you have a huge lathe, you'll feel it when makes contact. And you don't want it tight because the work piece will grow due to heat, which of course also varies by material, length, and how much material is being removed and how. So if you are getting after it and heating it up, you often have to back off the tail stock to keep it from overloading the live center.

Or you can get a concentric (or the like) spring loaded live center and mostly just go. I've got a couple of concentric (including a bull nose) and love them most center work. But for rough work, I use a big MT4 Skoda, or an even bigger MT4 Rohm with a semi-bull nose, both cheap off ebay because they are bigger than most want and have some wear rings on the points (probably from offset turning).

[Glenn Brooks]

What Russ said. It doesn't take much torque to properly apply a Live center in the tail stock (deadcenter of course goes in the headstock).

One thing I noticed when turning between centers in my old 7" Dalton Lathe, if I apply to much pressure to the work with the tailstock, the headstock bearings bind up and the work doesn't turn freely. So I loosen the tailstock until the work piece turns freely- yet is still held firmly in place with the two centers.

I imagine the actual torque is something between 5 and 15 pounds, but have never measured. Snug it down with the handwheel is the operative word!

Glenn

[ctwo]

I use a dead center in the tail stock on occasion. Sometimes I feel it is better.

I believe I load it up just a tad more than needed. I'm starting to think it just needs to touch with a very slight pressure.

[spro]

I probably cannot add much but I used dead centers a lot. They need constant lube to not gall or swell by heat but they still do. So there is checking the tightness and corrections. There are reasons for using them as they have minimal overhang when turning the right end of a part. Even with rocker/lantern toolholders, there can be areas of the compound which just can't pass the live center's head.

[ctwo]

That's it, spro. mostly for the smaller stuff. It just gives me a better sense of rigidity and feel. I use a high pressure molly.

[pete]

If you have the room to get a finger onto the live center one recommendation I've read is to start the tip into the center drilled end to support the work then keep moving the live center tip in while rotating the live centers point back and forth with your finger. Once the centers tip makes full contact tighten a fraction more until you can't rotate the centers point anymore with that finger. It obviously doesn't take much pressure for that to happen and seems to work well for me. For smaller work I just guess and use very light pressure. If the work starts to chatter add a fraction more. I don't know what it takes for real large and heavy work though. A seriously worn live center seems to take a lot more pressure. My guess is the bearings need much more of a load to keep the work from chattering.

[curtis cutter]

I am seeing this as a with experience I will become more familiar with what it takes pressure wise thing. I find myself adjusting as I go on occasions, most often after I encounter a problem such as the chatter you spoke of Pete. It is just that once I encounter the chatter I have caused a problem on a finish pass.

Since virtually none of the work I do is critical as to tolerance (mostly farm stuff), the occasional bit of chatter is of little issue. I just spend a lot of time trying to get a good finish and would like to be consistent in my output. My goal is; I would like to show people like you guys my work but at this point my shop door remains locked.

[earlgo]

I used a dead center in the tailstock for years before I bought a live center.($) BUT the important thing is to use a high pressure lubricant for the center. Oil won't cut it. You need the best HP Lube you can afford. Unfortunately now some of the lubes are as expensive as a live center. If you have a carbide tipped center, it is better than a HSS center.
The 'old guys' used white lead on the center and the older lathes had a little pocket drilled in the tailstock for the lead and dauber.

--earlgo

[John Hasler]

> The 'old guys' used white lead on the center and the older lathes had a little pocket drilled in the tailstock for the lead and dauber.

I still use dead centers (I'm too cheap to buy a live one and too lazy to make one). My Logan has a dauber hole for which I made a dauber. I find that anti-sieze works well as lubricant. I did burn up a center before I learned how to keep the pressure correct, though. It's easy to overdo it.

[ctwo]

I made a dauber for mine too, after watching tubalcaine make one... and that is where I put my HP grease. My Logan came with a cooked dead center, so I had an easy lesson of what could happen there.

[spro]

Cooked dead centers is probably my first use of a TP Grinder. First they had to be turned in the spindle with a carbide tool but then the grinder made a fine finish. Since I did about five of them with the same setup, I ground ball ends on the last two. Ball ends are good for taper turning a longer angle(without a taper attachment). Then I made two live bull centers, a 2" and 4 1/2". Used up a lot of tinfoil and cardboard to protect things.