Chewed up live centers

S

sasnecro

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Okay guys I'm at a dead end I need your help I've tried everything I'm going to post a link to a video of the situation that I'm having. I'm not sure if replacing certain parts on the tailstock will fix the problem.

 
You don't say if you indicated the inside hole, so try that 1st. It may not be concentric with the OD. Another thought is to slow the spindle down, put the center in and take a small cut off the OD while you have an INDICATOR on the dia. in front of the cut to see if it's jumping around.
 
If you are trying to use a center in the tailstock with a piece of stock with a predrilled hole in a three jaw chuck, there is a very good chance that the hole isn't aligned with the spindle axis. When you bring the tailstock center into the hole, you will get a deflection of the tailstock quill and/or the stock. But as the work rotates, the stock will flex, constantly changing its position on the center. This rubbing action will create the wear [pattern you are seeing.
Normally when using a tai;lstock center you would either cut the countersink for the center after mounting the work, thereby insuring concentricity or run between centers using a spindle center, a faceplate, , and a lathe dog.
 
RJSakowski said:
If you are trying to use a center in the tailstock with a piece of stock with a predrilled hole in a three jaw chuck, there is a very good chance that the hole isn't aligned with the spindle axis. When you bring the tailstock center into the hole, you will get a deflection of the tailstock quill and/or the stock. But as the work rotates, the stock will flex, constantly changing its position on the center. This rubbing action will create the wear [pattern you are seeing.
Normally when using a tai;lstock center you would either cut the countersink for the center after mounting the work, thereby insuring concentricity or run between centers using a spindle center, a faceplate, , and a lathe dog.
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I have chucked up some bar stock and then I board the center and faced it inside of the tube calibrated perfect so the center is definitely has no wobble but it will still leave marks on the live center
 
This might be a dumb question but did you put a 60 degree taper inside the end of the work piece? I f not, then do so. A sharp edge will score your center like you are experiencing.
 
When wanting a center in a piece of pipe you would need to plug the end of the pipe with a slug then cut the center. Like said above if using a center on a straight end cut of pipe it will leave a line.
What type of preload are you putting on the live center before turning? I like to barely be able to spin the center so when warm after cutting it is not putting extreme force on center or bearings.
How heavy of a cut are you taking? Tool pressure could be causing it. Do you oil the center before locking down?
 
Cadillac said:
When wanting a center in a piece of pipe you would need to plug the end of the pipe with a slug then cut the center. Like said above if using a center on a straight end cut of pipe it will leave a line.
What type of preload are you putting on the live center before turning? I like to barely be able to spin the center so when warm after cutting it is not putting extreme force on center or bearings.
How heavy of a cut are you taking? Tool pressure could be causing it. Do you oil the center before locking down?
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I never had this problem on the harbor freight. I don't oil. Med pressure. I only turn 6061 1-2 thousands a pass
 
sasnecro said:
What do you mean?
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I mean that if you put a live center into a hollow end of the work piece as you are doing, it will leave a contact mark like you are getting. The inside diameter of the work is contacting the nose of the live center with the sharp corner of the ID. I suggest you take a 60 degree countersink and taper the ID of the work so that you have a matching taper to contact the nose of the live center.
 
mikey said:
I mean that if you put a live center into a hollow end of the work piece as you are doing, it will leave a contact mark like you are getting. The inside diameter of the work is contacting the nose of the live center with the sharp corner of the ID. I suggest you take a 60 degree countersink and taper the ID of the work so that you have a matching taper to contact the nose of the live center.
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I will definitely try that but it is never done that before on the harbor freight not one scratch no matter how hard I pushed it in or light
 
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