Live center disassembly .

[DPittman]

I've watched a few videos but none of the methods I saw seemed applicable to this center. There is a cap that threads on (not shown) and I assume that was used to press the assembly in place. On the tail end there was a tiny (#10-24) set screw that I think was just a place to insert lube. I tried to pull the live center apart by clamping the center shaft in the three jaw chuck (wrapped in aluminum to protect shaft) and then retract it with the tailstock. No luck.
Any suggestions?

 

[YYCHM]

How does your tailstock attach to the taper such that you could back it out?

 

[Johnwa]

Try this video

 

[DPittman]

Try this video

Ya he just lifts the center out of the bearings, mine won't do that. I'm going to try pressured grease! I'm making an adapter right now that will screw into the tailstock center end where the Allen screw was and on that I will adapt a grease zero. Probably won't work but easy enough to try.

 

[Johnwa]

A thin punch through the set screw hole might knock the center out.

 

[RobinHood]

I think we are looking at the front of a shielded ball bearing (Second picture). There are probably two stacked up, one behind the other. Then there would be thrust bearing. The “tail” would be supported by a tiny needle roller bearing.

I would use a punch through the opening at the rear and drive the whole thing out the front. If you have an arbour press or a hydraulic press, it should come right out.

 

[DPittman]

As you can probably all guess the pressurized grease thing didn't work. The grease just squirted out the bearing holes in the shield. I was hopefull that maybe I could pump it in faster than it could escape and build a bit of pressure.

 

[DPittman]

I think we are looking at the front of a shielded ball bearing (Second picture). There are probably two stacked up, one behind the other. Then there would be thrust bearing. The “tail” would be supported by a tiny needle roller bearing.

I would use a punch through the opening at the rear and drive the whole thing out the front. If you have an arbour press or a hydraulic press, it should come right out.

I guess I will try that. I initially looked at that but because the opening is only about 5/32" and is about a 3-4" reach I was hesitant. I've already lost the set screw on the inside as I turned it in past the threads wondering if there was a stop. Nope there wasn't.

 

[DPittman]

Yup punching the assembly out from the back worked! It was all that a .155" diameter shaft could handle though. Now to examine.

 

[DPittman]

So I was expecting to find a tapered roller bearing in this center but there are just two regular ball bearings with a spacer in between. I wanted to take this apart as it felt slightly gritty to me, it may just be dirt but I think I will likely just replace both bearings to be sure.
The one bearing at the back is a rubber shielded bearing and the one at the front is regular steel shield. I'm not sure why they would use two different types. I like the idea of using two regular steel shielded bearings as that allows the grease to be squirted through them easily.

Is there any reason I should not replace the rubber shielded bearing with a steel shielded one?

 

[Johnwa]

What are the bearing numbers? One of them may be (should be) an angular contact bearing.

 

[Tom Kitta]

I rebuild many live centers - all of them Skoda. They are made of 3 bearings. Your construction is quite different. Mine was like Johnwa stuff, one thrust bearing, one angular roller bearing and one small bearing for the end. It looks like you have two large ball bearings. It is certainly cheaper but strange construction, it cannot take a lot of forces reliably.

 

[DPittman]

What are the bearing numbers? One of them may be (should be) an angular contact bearing.

They are both 6202. One rubber shielded and one steel shielded. And to my surprise the one is marked "Japan".

Construction is basically the same as Joe Pie's homemade center he uses in a drill chuck.

 

[Tom Kitta]

Standard ball bearings, you can replace them with quality of your choosing. My favorite seller on eBay is "Bohemian seal" from Czechia. You can choose how good of a bearing you want.

Certainly this setup will work but is just not as good as others, luck of thrust bearing means you cannot push the live center too hard into the work & short shaft with just two ball bearings as per my understanding will not spin as true as others under heavier load. Heavier load for say MT4 is like more then few hundred lbs. So maybe why these are marked "light duty".

When I build my own chuck rotating on an old live center I used 4 bearings, two ball bearings + one thrust at the front and one small ball bearing at the end.

 

[DPittman]

Standard ball bearings, you can replace them with quality of your choosing. My favorite seller on eBay is "Bohemian seal" from Czechia. You can choose how good of a bearing you want.

Certainly this setup will work but is just not as good as others, luck of thrust bearing means you cannot push the live center too hard into the work & short shaft with just two ball bearings as per my understanding will not spin as true as others under heavier load. Heavier load for say MT4 is like more then few hundred lbs. So maybe why these are marked "light duty".

When I build my own chuck rotating on an old live center I used 4 bearings, two ball bearings + one thrust at the front and one small ball bearing at the end.

Yes this is only a mt2 live center. My way of thinking is that a great push load into the center should be easily avoided in most cases. If you have a good mating surface between the center point and the drilled center hole on the work there shouldn't be a great need to force it into the work.

Possibly this live center is one of the reasons I have had one hell of a time getting my tailstock adjusted right, I always seemed to turn a bit of a taper one way or the other.

 

[DPittman]

And here is another center I have. It has NO morse taper access whatsoever, they must have pressed it all in the front and I assume that it would never be able to be disassembled.

 

[Tom Kitta]

No MT live center is as accurate as a dead center (I guess disclaimer here it has not be a nice dead center) - but better brands do far better job then cheaper ones - again "better job" is up for debate - depends on your tolerances.

 

[Tomc938]

Thanks for sharing your process with us. Great way to learn something new. (and get other minds working on the problem)

I have a newbie question: What would cause the centre to be ridged like it is? If the centre and the piece are both spinning I would think the centre should be pristine.

 

[DPittman]

Thanks for sharing your process with us. Great way to learn something new. (and get other minds working on the problem)

I have a newbie question: What would cause the centre to be ridged like it is? If the centre and the piece are both spinning I would think the centre should be pristine.

I don't recall the exact circumstances that caused those ridges in my center, however I can imagine that it was likely cause by pushing the center into a less than perfect matching hole (likely a pipe of some sort). Your right because it is a spinning center one would expect that it should remain mostly pristine as there would not be any resistance to cause such friction marks.
The ridges appear MUCH worse in the picture than they actually are. The worst one I can just feel with a fingernail.

 

[Susquatch]

have a newbie question: What would cause the centre to be ridged like it is? If the centre and the piece are both spinning I would think the centre should be pristine.

What ridges are you talking about? The grooves in the nose piece itself?

I think those can happen when a part slips in the chuck, or the tailstock backs off a bit, or a lot of pressure is applied to the center against a sharp edged hole, or a heavy part starts vibrating, or when you are parting and the end piece starts wobbling just before falling off, or when the live center doesn't spin, etc etc

Hope that's what you are asking about.