# Did I Do the Right Thing?: Live Center



## Splat (Jun 10, 2014)

So I wanted to get a live center for my Heavy 10. Right now I just have two dead centers. With Nels kindly posting about Enco's 20% off and free shipping (>$200) I figured it was a good time to order *this* Royal spring loaded live center. I had planned on using this for any jobs requiring a center on this Heavy 10. One thing I have read IIRC is that you should use a dead center when knurling. I do plan on knurling some 1/2"x20" aluminum rods.  So I guess I have two questions. Should I use the dead center when knurling? Did I do right ordering this spring loaded Royal or should I have went with something else? Thanks.


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## xalky (Jun 10, 2014)

I don't see anything in the item description that specifies that this is a spring loaded live center. Live centers should not be spring loaded. The spring would negate the effect of the center and cause it to push back. 

You can use a good heavy live center for knurling.


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## Don B (Jun 10, 2014)

I would use the dead center for knurling, knurling takes quit a bit of force and theres no sense exposing the bearings in your live center to that if its not necessary, and the dead cent leaves less sticking out of the tailstock as well, it will make for a more ridged setup, knurling is done a low rpm so a dead center is fine for this.)

Edit: use a little oil on the tip of the dead center.)

Edit: sorry the force I was referring to was the kind that would be applied during conventional knurling if your using a scissor knurling tool this is a different thing all together, with the scissor knurling tool the force is being applied to the scissor mechanism and not directly to the head and tailstock)


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## darkzero (Jun 10, 2014)

That is a spring loaded center & Royal makes some of the best live centers, no doubt about that. Concentric/Riten is the other popular spring live center. I have always been curious about these but understood these to be used more with CNC. If they didn't cost so much I'd probably try one for the hell of it. I believe they only have about 10 thou of travel, to set them bottom out the spring then back off a bit. I'm not sure how much spring tension these have but they must be much more than the spring centers used for tapping. If they don't have a lot of spring tension I don't understand what the advantages they would have over a non spring loaded live center.

A good medium to heavy duty live center is fine for knurling. I've had no problems knurling using my Skoda live centers but I also use a scissor knurling tool. And I mostly knurl Ti 6-4. Wouldn't see the spring loaded live center to be good to use for knurling though.


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## Tony Wells (Jun 10, 2014)

Sprung live centers are designed to allow for material growth from temperature, and yes they have limits. I would not consider them for general use, myself. As far as knurling goes, clamp/scissor types are fine with it, but the bump style probably not. 

I never use a dead center in the tailstock. I have some live centers for roughing, and some for finish work. I never mix the two.


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## Bill C. (Jun 10, 2014)

Splat said:


> So I wanted to get a live center for my Heavy 10. Right now I just have two dead centers. With Nels kindly posting about Enco's 20% off and free shipping (>$200) I figured it was a good time to order *this* Royal spring loaded live center. I had planned on using this for any jobs requiring a center on this Heavy 10. One thing I have read IIRC is that you should use a dead center when knurling. I do plan on knurling some 1/2"x20" aluminum rods.  So I guess I have two questions. Should I use the dead center when knurling? Did I do right ordering this spring loaded Royal or should I have went with something else? Thanks.



How much of that 1/2" shaft is to be knurled? You may want to use a follower rest to support a long knurl. Make sure the rest is in front of the knurl. I would use a dead center if it was me.  

The manufacturer of your center should have engineered their center to support all the stress loads.  Wouldn't hurt to ask the distributor if it will work under knurling pressures.  

Let us know how the part came out or post a photo.


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## chuckorlando (Jun 10, 2014)

If you dont mind.... What are the reasons for using a roughing and a finishing center? How would you determine which center you would buy for either operation?





Tony Wells said:


> Sprung live centers are designed to allow for material growth from temperature, and yes they have limits. I would not consider them for general use, myself. As far as knurling goes, clamp/scissor types are fine with it, but the bump style probably not.
> 
> I never use a dead center in the tailstock. I have some live centers for roughing, and some for finish work. I never mix the two.


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## Tony Wells (Jun 10, 2014)

Really pretty simple. As we know, hot material expands, and that requires that you back off the center a bit if you have a slender piece, especially. Otherwise, the bearing wear is accelerated. In my case, it's eve simpler. I have some with many miles on them, they aren't dead true and I don't mind pushing them pretty hard. Then I have some that I keep virtually like new, for when I need a very close, repeatable runout to a center hole. Also, I have a couple that are bent, yielding a little taper. If I have a lot of stock to remove, I'll rough it it with one of those, then switch out to a good one to finish. 
Just to clarify, I consider a good center to run within 0.0002, and anything more than that is a rough center. And I have some that are scarred up a bit, like some of the bull centers..good for roughing, and some good ones for finishing.


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## Ray C (Jun 10, 2014)

Tony pretty much nailed it...  FWIW, when I need a good center, I switch to carbide tipped dead centers.  Most of my live centers run pretty true and are capable of very good work.


Ray


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## chuckorlando (Jun 10, 2014)

You see thats the kinda stuff years of experience will learn ya. That would never have crossed my mind till I was trouble shooting the problem caused for lack of such experience.


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## Frank Ford (Jun 16, 2014)

xalky said:


> I don't see anything in the item description that specifies that this is a spring loaded live center. Live centers should not be spring loaded. The spring would negate the effect of the center and cause it to push back.
> 
> You can use a good heavy live center for knurling.



Maybe not in that description but it is spring loaded.  I use a similar one by Concentric, and it's dandy - makes up for heat expansion of the workpiece.


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## george wilson (Jun 17, 2014)

I have a compact little Royal spring loaded #2 Morse taper center that I use a lot on my HLVH lathe for small work. But,it is not the type center for resisting much of a sideways load,like in knurling. It has a slender CNC type center in it that gives more room to get a turning tool all the way to the end of the work. It also slightly increases the distance between centers on my HLVH,which is not a very long lathe.


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## Splat (Jun 19, 2014)

Thanks guys. So I should only use the spring live center on small diameter parts? Darn. I thought it would be a perfect do-all live center but it sounds like I should get a "regular" live center afterall.


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## Cactus Farmer (Jun 19, 2014)

It has been mentioned previously about oil on a dead center. I always use white lead (Oh,horror, it's poison!). It's what the old timers used before live centers were common. I know it's no longer available at stores but I have found a lifetime supply at flea markets and yard sales.
Even if it's hard as flint it can be softened with a little solvent. It was usually made with linseed oil I hear. Any paint solvent seems to work well if given time to work. The normal precautions apply about WL, no eating and wash your hands after being exposed. I do this anyway, the dark sulfur cutting oil is NOT a condiment in my house. YMMV


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## darkzero (Jun 20, 2014)

Splat said:


> Darn. I thought it would be a perfect do-all live center but it sounds like I should get a "regular" live center afterall.



Unfortunately there's no such thing. I would definitely consider a medium to heavy duty center & later on if needed an extended nose live center as well as a bull nose (bull nose not so much depending on your needs).


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## george wilson (Jun 20, 2014)

The spring loaded center is not necessarily relegated to very small parts,but should not be used with heavier parts either. It requires a little common sense is all. The tip is spring loaded,and you must recon with how large a load it can sustain without retracting the tip. And,take light cuts.


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