About the (many) live center types?

[graham-xrf]

Up to now, I have so far used dead centers (my needs were modest). I try to research as much as I can before I buy, and I do intend to trawl everything about live centers. I am struck by how many brands, and shapes, and sizes there are, this quite aside from needing the right Morse taper. Lots of them are reviewed on woodwork sites, and I don't know if any styles are just dedicated to wood turning loads.

Just as example, a single advertisements shows these ..



So far, I have understood that one should look for pre-loaded three bearings. Those shown in the picture claim accuracy 0.001", which, for what it does, that sounds kind of poor to me. I had expected something at least into tenths, if not microns.

As for the shapes, some are cones, some are two-angles cones, some are short, some are called "bull-nose". What is the motivation to use a particular shape?

I will be trying to dig around in the searches here, but I would appreciate a basic pointer on what not to buy.

I will be wanting a MT2 and I consider also for the future, a MT3 for the headstock spindle, to turn between centers with a dog drive from a faceplate.

 

[Jim F]

You will want a dead center for the spindle.
As for the lives, a bull nose fits a large opening, like a pipe and such, the rest are select as to the dimension of your work piece and ho close you need to get.
Run-out , you can get some that are near zero.
You get what you pay for with live centers......
Something else to consider is body size.

https://www.mscdirect.com/product/details/70793138

 

[graham-xrf]

Run-out , you can get some that are near zero.
You get what you pay for with live centers......
Something else to consider is body size.

https://www.mscdirect.com/product/details/70793138

We agree on paying for quality. I guess I don't agree to pay unreasonably for a "quality" where 90% of the price is expended to achieve a claimed quality that is perhaps only 5% to 10% improved over a competing lower priced product.

The Royal Products live center costs $ 731.17 , reduced from $860.20, which is 15%
It can run at 6000RPM, which compares to 3000-5000RPM for Chinese origin eBay kit around $25
It can handle 1270lb thrust and 885lb radial load.
I could not see any specifications for accuracy, run-out, etc. for the Royal product. For as much as $860.00, this we decide had better be good!

- - - - - - - - - - - - - - - - - -
A low cost eBay 3500RPM product for about $22.50, although claiming triple bearings, can only say the "max workpiece weight" is 265lb.
I look to this cheapo product specifications, which are just confusing ..

Concentricity: 001"
Accuracy: 0.0002"
Angle: 60º
Max RPM: 3500
Max weight of work piece: 265lbs

It makes no sense! I know how concentricity is normally defined.
A value 0.001" is not going to impress me, but 0.0002" begins to, if I knew what was "accuracy" in this context.
- - - - - - - - - - - - - - - - - -

I get it that there may be some industrial processes that are so very critical, that $860 is considered OK for the purpose, but they must be very, very, super-special. Making valves for spacecraft, missile launcher kit for F35's and the like. Even so, one has to wonder how much added value,and change in running specification racks up a a price difference like in the examples I cite. It gets near impossible to come to a reasonable understanding of the intrinsic value. The Royal Products offering may be good - but can it be forty times as good?

Of course, I am never going to spend on a live center more than the value of the lathe it goes on! I am also not going to purchase anything that has a concentricity specification as poor as 0.001".

If you want to see why the Royal Products live center cost what it does, here is the answer in their blurb..

 

[Jim F]

Features

• All Royal Live Centers are guaranteed accurate to +/- 0.00005" TIR or better

 

[Jim F]

I have a Craftsman live center that came with my lathe, it is damaged, but still works.
I also bought a kit similar to this.

2 MT Morse Taper Medium Duty Live Center Set

www.shars.com

Has worked for me so far.

 

[NC Rick]

I'm using a Shars extended nose "live center" on my lathe but it's an MT4. It has worked well for me. I don't know the runout but it's better than what I need. I still have the old "Motor Tool" Company" MT2 standard live center from my delta. The extended nose "CNC type" is the way to go imo. I'll be getting a Bull nose one in future. Nothing like 800 bucks for the two of them combines. I'd love a royal... my collet closer is a Royal and it's pretty good. My Shars gets used a good bit and is 3years old or more.

 

[benmychree]

If I bought a new live center, I likely would look for a European brand, definitely not Chinese, and yes, the extended nose type is a good thing for light and medium weight workpieces; the extension means deformation or flexibility at higher loads, If you have a machine with ridgdity and power, better to have a heavier center that allows heavier cuts, and perhaps a extended nose for work requiring it in terms of accessability to the end of the workpiece with tooling.

 

[Aukai]

I just found a Royal 10663 for 535.00, it's relisted at 599.00

 

[Bi11Hudson]

I've got to butt in here to confound the issue a little more.

In the older texts, including catalogs until fairly recently, a "live" center was an unhardened center for use in the spindle. Unhardened to allow it to be trued in place when necessary. Live in that it rotates with the work, so only needs to be centered, not a bearing surface.

A "dead" center, on the other hand, is for use in the tailstock. Where it remains stationary as the work revolves around it. It is hardened because it serves as a bearing surface as well as a centering device. With thar clarified, the discussion procedes to the many styles of centers, such as "ball bearing", "bull nose" and the like.

A reference from above, the "adjustable" center is a good all around tailstock center. I use one, although not such high quality.

2 MT Morse Taper Medium Duty Live Center Set

www.shars.com

Has worked for me so far.

The insert allows me to get in close on the end with the bearing clear of the tool. The tradeoff though is it doesn't have the strength for heavy cuts. For that, I use a ball bearing center with a full size point. I do keep a hardened dead center for if I ever need it, but it gets little use. I don't do "precision" work, usually a thou. Occasionally (rarely) to a half a thou. As such, my need for accuracy is small. With accuracy comes cost. For what I do, I can't justify a high accuracy tool. If I happen onto one at a reasonable cost, I grab it. Otherwise, I make do with whatever I have.

The only real advice I can offer is to avoid anything specified as a "wood working" tool when doing metal work. I use my metal working centers on a wood lathe occasionally. But definately avoid going the other way.

.

 

[Jim F]

I've got to butt in here to confound the issue a little more.

In the older texts, including catalogs until fairly recently, a "live" center was an unhardened center for use in the spindle. Unhardened to allow it to be trued in place when necessary. Live in that it rotates with the work, so only needs to be centered, not a bearing surface.

A "dead" center, on the other hand, is for use in the tailstock. Where it remains stationary as the work revolves around it. It is hardened because it serves as a bearing surface as well as a centering device. With thar clarified, the discussion procedes to the many styles of centers, such as "ball bearing", "bull nose" and the like.

A reference from above, the "adjustable" center is a good all around tailstock center. I use one, although not such high quality.

The insert allows me to get in close on the end with the bearing clear of the tool. The tradeoff though is it doesn't have the strength for heavy cuts. For that, I use a ball bearing center with a full size point. I do keep a hardened dead center for if I ever need it, but it gets little use. I don't do "precision" work, usually a thou. Occasionally (rarely) to a half a thou. As such, my need for accuracy is small. With accuracy comes cost. For what I do, I can't justify a high accuracy tool. If I happen onto one at a reasonable cost, I grab it. Otherwise, I make do with whatever I have.

The only real advice I can offer is to avoid anything specified as a "wood working" tool when doing metal work. I use my metal working centers on a wood lathe occasionally. But definately avoid going the other way.

.

A live center, the contact point spins on bearings, a dead center locks into the taper. Great for the spindle to drive, not so great for the tailstock.