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when do you use a live center instead of a dead center?

Ken from ontario

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#1
I've been asking myself this question for a while and don't exactly know at what point does one need to move from a dead center to a live center?
Is it because with a live center you can put more pressure to the center of the workpiece and therefore cut more precisely? or does it have something to do with the size of the workpiece?
If you use a well lubed dead center and there's no sign of the tip overheating, why would you use a live center than?
could you explain that for me.
Does the live center always go in the headstock?
 
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T Bredehoft

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#2
The live center goes only in the tailstock.
In My Opinion"
Live centers are good enough for anything I do on my lathe. Granted it's a small lathe, and I don't have many demanding jobs.
Dead centers, I'd use in a cylinder grinder. (anything round) There's little pressure (comparatively) on the center.

Time was.... before the development of dependable live centers... that dead centers were all that there were.
 

chips&more

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#3
Interesting question. The dead center was first to happen and then I guess someone came up with the live center idea because of some of the dead center pitfalls. Nowadays IMHO, if you can afford/justify a good live center then get it. Maybe also get a dead center just because.
 

Ulma Doctor

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#5
i was taught to work with dead centers, they will produce work with less runout than a live center-
although the tolerances on live centers now is near enough to make them very accurate and suitable for most work any of us will ever do.
i still use dead centers when turning between centers or when threading
 
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mikey

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#6
I've been asking myself this question for a while and don't exactly know at what point does one need to move from a dead center to a live center?
Is it because with a live center you can put more pressure to the center of the workpiece and therefore cut more precisely? or does it have something to do with the size of the workpiece?
If you use a well lubed dead center and there's no sign of the tip overheating, why would you use a live center than?
could you explain that for me.
Does the live center always go in the headstock?
Nowadays, most of us use live centers for almost all work and yes, a live center goes into the tailstock. There was a discussion not long ago about the nomenclature of dead centers and supposedly the solid centers that go into the headstock are "live" centers and the ones that go in the tailstock are "dead" centers. While interesting, the reality is that most of us use tailstock centers with bearings inside them and we call them Live Centers.

As mentioned, a live center is usually used most of the time because it does not require us to stop the lathe and lube the tip of this center. When using a dead center, you have to stop the lathe from time to time to re-lube the tip of the center and then readjust the tailstock pressure because the work piece will heat up and expand from friction between the dead center and work piece.

So, when is a dead center used? It is most often used when we want the ultimate in accuracy, either to turn a precision work piece "between centers" or when using a test bar to align a tailstock. Otherwise, most of us just use a live center.

Not all live centers are created equal. I use a Royal live center and it is very precise, with no discernable play. Cheap live centers can have enough play to affect accuracy, especially when turning big, heavy work pieces so buy a decent one.

Hope that helps.
 

pdentrem

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#7
Rotating centers only go in the tailstock as stated earlier. Dead center can go in the spindle or the tail stock.

One advantage to using dead centers is you can make a custom one fairly easily. Once it is cut and ground in the spindle it is accurate while a rotating center is dependent on the quality of the bearings and the other components. I also only use dead centers in our Landis Cylindrical grinder they are the most accurate. We need to be inside of 0.0002" in roundness and when making match sets of rolls for rolling mills, dead centers are the only way to get this kind of accuracy.

At home, I have used both with varying success. My rotating center is only a mid grade, maybe 0.002" but I questioned that ever since I had it. Never checked as I never had a home job to be that good. Only $200 vs a lot more for a real nice one. YMMV
Pierre
 
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4gsr

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#8
Spend the extra $$$ and get a nice name brand live center to use.

I recently bought one of those cheaper $30 live centers to put with the 13" lathe I sold. What a joke! I could flex the center up and down enough you could see the movement. Of course, put a load on it and I couldn't get it to move. I don't get that with my other German made live centers I have.
 

mikey

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#11
Thank you all for your comments and advice.
I know good tools such as Royal live center costs more money but , $350 for for a Royal ? and that's the least expensive one.
http://www.traverscanada.com/search.aspx?keyword=live+centers
I would not buy a Royal or any other live center at retail prices. Use what comes with your lathe and watch for a deal on ebay. Brands to look for are Royal, Skoda and Riten (there may be others). Rohm makes good ones, too. Typically, a new Skoda will go for about half what a Royal costs on ebay, like this one:

http://www.ebay.com/itm/SKODA-Preci...944974?hash=item1c85af568e:g:oTQAAOSwSypY-T5C

I would make an offer for $100.00 and see if he bites.

I have an interchangeable tip Royal. Its good to know that they are warranted for life and if you have a new tip, Royal will grind it to suit your specific live center body for free, for life.
 

Glenn Brooks

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#12
Rotating centers only go in the tailstock as stated earlier. Dead center can go in the spindle or the tail stock.

One advantage to using dead centers is you can make a custom one fairly easily. Once it is cut and ground in the spindle it is accurate while a rotating center is dependent on the quality of the bearings and the other components. I also only use dead centers in our Landis Cylindrical grinder they are the most accurate. We need to be inside of 0.0002" in roundness and when making match sets of rolls for rolling mills, dead centers are the only way to get this kind of accuracy.

Pierre
+1 on this! Dead centers go in the headstock, because you can easily turn them down to be concentric with the center line of the lathe. No need to worry about runout in the chuck. Instant alignment with the tailstock! Also, turning between centers is a great way to work with long work pieces. Like axles with wheels pressed on. Once I did this a few times, it became my go to method for turning long work in the lathe.

Glenn
 

darkzero

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#14
Nowadays, most of us use live centers for almost all work and yes, a live center goes into the tailstock. There was a discussion not long ago about the nomenclature of dead centers and supposedly the solid centers that go into the headstock are "live" centers and the ones that go in the tailstock are "dead" centers. While interesting, the reality is that most of us use tailstock centers with bearings inside them and we call them Live Centers.

As mentioned, a live center is usually used most of the time because it does not require us to stop the lathe and lube the tip of this center. When using a dead center, you have to stop the lathe from time to time to re-lube the tip of the center and then readjust the tailstock pressure because the work piece will heat up and expand from friction between the dead center and work piece.

So, when is a dead center used? It is most often used when we want the ultimate in accuracy, either to turn a precision work piece "between centers" or when using a test bar to align a tailstock. Otherwise, most of us just use a live center.

Not all live centers are created equal. I use a Royal live center and it is very precise, with no discernable play. Cheap live centers can have enough play to affect accuracy, especially when turning big, heavy work pieces so buy a decent one.

Hope that helps.
Yeah quite the confusion when the old timers chime in about it. I was taught by an old timer who said dead centers are used in the tailstock & live centers are used in the headstock, meaning when a solid center is used in the headstock or whenever it rotates with the part, it's "live" & when a solid center is used in the tailstock (not rotating) it's "dead". I suppose that is how it was befor ball bearing centers were invented?

That's not how they are called today. Look at any vendor or manufacturer & a live center is a ball bearing center & a dead center is a solid center. That's how I'm used to it & that's how I call them too to avoid confusion despite what I was "taught". I suppose I should stop saying "live" & "dead" and should start saying "roating" or "ball bearing" and "solid" but I don't think I will. :)

I would not buy a Royal or any other live center at retail prices. Use what comes with your lathe and watch for a deal on ebay. Brands to look for are Royal, Skoda and Riten (there may be others). Rohm makes good ones, too. Typically, a new Skoda will go for about half what a Royal costs on ebay, like this one:

http://www.ebay.com/itm/SKODA-Preci...944974?hash=item1c85af568e:g:oTQAAOSwSypY-T5C

I would make an offer for $100.00 and see if he bites.

I have an interchangeable tip Royal. Its good to know that they are warranted for life and if you have a new tip, Royal will grind it to suit your specific live center body for free, for life.
I'm also a believer of not using cheap live centers. I can't afford a Royal or Riten & never was able score a nice one used. I've been using Skodas & I like them. They're the best bang for the buck for live centers IMO.

If you look in the right places, one can get a Skoda for a very good price. Like that MT2 Skoda in the ebay link for $125, I used to have that same one. Earlier this year, I sold both my MT2 & MT3 Skodas & upgraded to their latest ones. I guess they decided to make a change to them cause so many are copying them. I got MT2 Skoda from MSC, brand new for $116 shipped, it was dropped shipped directly from Sowa.

I also have a couple of live centers from Z Live Center. I'm not sure where they're made but I just assume Asian import and I was very hesitant to buy one from them at first but I have their "CNC Precision Long Spindle" live centers & it's actually pretty nice. I've bought a few things from them & I like the company. Just last week I ordered something, they sent me the wrong item by accident, told me to keep the incorrect item & shipped me the correct item.

 

4gsr

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#16
Here's a Rohm German made live center I saved in a dumpster dive 28 years ago. It had the word "BAD" written on it with a yellow paint pen when I found it. The center point has a few idiot marks on it, but amazing the runout is "zero". Could use a cleaning, not as pretty as Will's, gets the job done!
 

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Ken from ontario

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#17
Yeah quite the confusion when the old timers chime in about it. I was taught by an old timer who said dead centers are used in the tailstock & live centers are used in the headstock, meaning when a solid center is used in the headstock or whenever it rotates with the part, it's "live" & when a solid center is used in the tailstock (not rotating) it's "dead".
Confusion, that's what I found when searching the net for" live center vs dead center", it seems a lot of old timers are of the opinion that live center should go in the headstock! probably based on the same logic you mentioned above.needless to say the opposite makes more sense to a novice like me but it's good to know both sides of the argument.
 

Ken from ontario

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#18
Here's a Rohm German made live center I saved in a dumpster dive 28 years ago. It had the word "BAD" written on it with a yellow paint pen when I found it. The center point has a few idiot marks on it, but amazing the runout is "zero". Could use a cleaning, not as pretty as Will's, gets the job done!
What a find, after watching a few youtube videos , it looks like refubishing/repairing these older live centers is quite common.
 

4ssss

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#19
I'm one of those old timers and I was taught to use live centers in the tailstock EXCEPT when knurling or doing an operation that puts pressure against the center.
 

Bill Gruby

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#20
The only time I use a "Dead Center" is when I need clearance. Then I use a "Half Center". All other applications take the "Live Center".


"Billy G"
 

benmychree

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#21
Another note on solid centers; The center that is used in the headstock has a vee slot turned in the shank on the taper that fits the spindle taper, this is to signify that it is soft at the point; this is so that it may be trued up by re-cutting if it runs out. The tailstock center is hardened and has no such slot and must be ground to true it up, although carbide tools of a harder grade, such as Kennametal K-6 will cut most hard parts.
 

Bob Korves

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#22
I've been asking myself this question for a while and don't exactly know at what point does one need to move from a dead center to a live center?
Is it because with a live center you can put more pressure to the center of the workpiece and therefore cut more precisely? or does it have something to do with the size of the workpiece?
If you use a well lubed dead center and there's no sign of the tip overheating, why would you use a live center than?
could you explain that for me.
Does the live center always go in the headstock?
As noted, we recently had this same discussion. I will repeat what I said there. The nomenclature and the associated meanings of the terms "live" and "dead" centers have become so hopelessly convoluted over time that I will only say "solid" and "ball bearing" to describe types of centers -- at least in public discourse. Call it anything you want if you are only talking to yourself...
 

Silverbullet

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#23
If you Ck textbooks any center used in a head stock is live , in the tailstock it's called dead. Just to use the official teaching method. So a ball bearing center we call live really isn't unless you put it in the head stock. I always thought it was bassakwards. But I try to say it the right way.
 

Wreck™Wreck

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#24
Use a rotating center when running a spindle speed that is entirely too fast for a non rotating tool, the difference will become obvious with time (-:
 

benmychree

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#25
I think that may well be the best approach, but to be a little factious, when we cylindrical grind, generally on dead centers, we have the option of running the headstock center either stationary or rotating; live or dead ??????????? Personally, I think the live center is of the anti friction bearing type, and dead centers are of the solid type, whether they rotate or not
 

pdentrem

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#26
We also keep the center in the headstock still and only have the face plate driving the dog. Makes a better grind.
Pierre
 

benmychree

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#27
We also keep the center in the headstock still and only have the face plate driving the dog. Makes a better grind.
Pierre
Yes, I have always done so, personally, it is the correct way to do the operation, but my point was that the same article could be describe as being both live and dead in the same spindle. Personally I think that this whole discussion has been a bit on the silly side; as far as modern usage has it, I think both centers are dead if they are solid, but perhaps we just need to stop splitting hairs and just say "turning on centers".
 

pdentrem

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#28
In doing a bit of research, dead, live, rotating etc etc has regional, country and cultural variances. I look at it as - if driven it is live, stationary - dead, and rotating means with some sort of bearing. This is how I explained it to the new guys even if they just came out of school/apprenticeship that way we are all on the same page. Any confusion can lead to errors and scrap parts or rework.
Pierre
 

Ken from ontario

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#29
Thank you all for your opinions and inputs, I read all of your comments with a lot of interest but mainly to clarify the usage of centers, which means , under what situations do I reach for a "solid" center or "ball bearing" center .
I got the answer to my question (and the majority of you agreed )with post #5 and #6, although it was really interesting to read all the rest of your comments about the reasons why they are called live or dead centers and where it originated from .I learned a lot from all your opinions .
Again thank you all .
with dead centers, the will produce work with less runout than a live center-
.
i still use dead centers when turning between centers or when threading
Nowadays, most of us use live centers for almost all work and yes, a live center goes into the tailstock.

As mentioned, a live center is usually used most of the time because it does not require us to stop the lathe and lube the tip of this center.

So, when is a dead center used? It is most often used when we want the ultimate in accuracy, either to turn a precision work piece "between centers" or when using a test bar to align a tailstock. Otherwise, most of us just use a live center.
 
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