Did I Do the Right Thing?: Live Center

[Splat]

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.

 

[xalky]

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.

 

[Don B]

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)

 

[darkzero]

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.

 

[Tony Wells]

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.

 

[Bill C.]

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.

 

[chuckorlando]

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?

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.

 

[Tony Wells]

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.

 

[Ray C]

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

 

[chuckorlando]

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.