OK, what's up with this live center?

[Carole in VA]

I ordered a 60 degree live center (Grizzly) for my Jet mini because I noticed the mandrel was putting undue wear on the original tailstock center. When I mounted the new one, snugged it up to the mandrel and turn on the lathe, smoke started coming from the juncture and the tip of the mandrel around the threads started turning black. The center was spinning but apparently not at the same speed as the mandrel, thus the heat build up. I quickly turned the lathe off and figured I better ask some questions before I ruined something (if I haven't already!)

 

[daledut]

I hate it when people answer a question with a question, but that is what I am going to do.[8D]

Does the live center turn freely by hand (not stiff or bound up)?

Is there sufficient pressure between the point and the mandrel to cause drive? (you should not have to bow the mandrel to get the center to spin)

If the answer to both is yes then I am not sure I know what is happening. If the answer to #1 is no, then I would call Grizzly for a replacement. If the answer to #2 is no then add a little more pressure and see if it helps.

I have a center from Grizzly and it works fine, so I would not hesitate to call them.

 

[Fred in NC]

Carole, would you post the model number of the live center?

Did the center turn freely by hand? Does it turn freely now?
Maybe we can figure it out.

 

[Carole in VA]

The center seems to turn OK by hand. Not quite a freely as the original, but then it is a heavier center (Model G5686) than the Jet original. Tightening it up does not stop the problem. Did I mess up the mandrel?

 

[Fred in NC]

Carole, looked it up... that is a very heavy duty live center.
I use a lighter one than that, and it works well. Maybe the grease inside is not 'broken in' yet. Maybe it is cold where you are working, and the grease is too stiff.

Tightening it too much against the mandrel will bow it. You can check it against any flat surface, and also by rotating it by hand (using the handwheel) with the tip of the mandrel about 1/8" away from the tip of the live center.

One more possibility is that the recess in the end of the mandrel is not really a true 60 deg. angle. In that case, only the tip of the live center will contact metal in the mandrel. The sharp tip does not produce enough friction to rotate the live center, but enough to produce heat. Check this out also. If that is the case, you can verify it by putting 2-3 layers of tape (masking, etc.) between the mandrel and the tip. If it works better, then the problem is with the hole in the mandrel not being 60 deg. also.

Hope this helps.

 

[Carole in VA]

Which one do you use, Fred? Model#? I did not realize that center was going to be a "substantial" as it is. Grizzly's description made me think it was a good center for any lathe. It is cold in the shop, btw, but as I said, when I turn it on the center does spin, but it is obviously not spinning as fast as the mandrel. I am wondering if I didn't ruin the mandrel with the original center that was provided with the Jet.

 

[DCBluesman]

Carole...first, if anything I say differs from Fred in NC, take his explanation. He's one of the best machine guys I know here. That being said, it is possible that the old center damaged the cup end of the spindleIf the center and the cup are not lining up perfectly you may get some spin. That, coupled with the packing grease could cause the smoke you are referring to. To check the cup, get your eye on level with the spindle, then press the spindle against the center. Hand rotate the lathe and look for defects in the cup at the point where it presses against the center. If there is play in this area, I would suggest replacing the spindle. The spindle portion of the mandrel can generally be replaced for about $3 as opposed to $9-10 for the entire mandrel. You have now reached the capacity of what Fred has been able to teach me over the months.

 

[Fred in NC]

Lou, you are right on track, and I am not such an expert, just a tinkerer at heart. But thanks anyway !!!

Carole, please do the test with the masking tape, OK, and let me know. At least a 'buffer' could help you until you get this resolved.

I will look up a live center stock number, and let you know.

ADDED:

This is exactly what I use:

http://www.littlemachineshop.com/products/product_view.php?ProductID=1189

I would call Chris on the phone, very nice and helpful guy.

However, if your mandrel shaft is damaged, you might need another one.
Mine is from Woodcraft, $9.95 and is a perfect match to the live center.

 

[DCBluesman]

Kudos from Fred! Now I know how "Grasshopper" felt.[] (See Fred...I pay attention, even to those wee hours of the morning conversations.) [8D]

 

[Carole in VA]

Originally posted by DCBluesman
<br />If there is play in this area, I would suggest replacing the spindle. The spindle portion of the mandrel can generally be replaced for about $3 as opposed to $9-10 for the entire mandrel.

Yeah, $3 plus $8 shipping plus 5-7 business days (excluding holidays.) I bet I have spent more in blasted shipping in the past month than I paid for the lathe!!!!! Darn, I hate living in the sticks sometimes!!!!
Maybe if I just turn the darn thing on and let it smoke, it will form it's own seat in the spindle. Or maybe I should just stick the Jet original back on and let it continue to self destruct.
Sorry for the rant...been a long day spent at the hospital, Xmas is closing in, I have pens to get done and now this. Grumble, mutter, cuss..... think I will go to bed, get some sleep and in the morning, I will just pop the old one back in.

 

[Fred in NC]

Carole, try the masking tape .....

 

[DCBluesman]

Carole, listen to Fred.....

 

[Carole in VA]

Originally posted by Fred in NC
<br />Carole, try the masking tape .....

I will in the morning. Thanks a bunch guys. Sorry for my rant....been one of those days. [B)]

 

[Randy_]

You can get a new mandrel from Berea for only $6 and they only charge $3 for shipping. Only question would be whether the thread on the mandrel that you have is the same as the one on the Berea mandrel. I would guess that most use a standard thread size but there are no guarantees. You might need to make a phone call to Berea to sort out that issue.

 

[RussFairfield]

Soak it in kerosene overnight. If that doesn't free it up, send it back.

No kerosene?? Use Mineral Spirits and add a tablespoon of mineral oil or baby oil? No mineral oil? Use cooking oil, or anything else that is slippery.

 

[Daniel]

Good morning Carole,
Hopefully some rest has givin you a second go at this. first I don't think your mandrel is ruined, and secondly I just took a brand new two bearing Live center out of it's box yesterday. I read your comment about yours not turning so I checked this one. it does turn smoothly but hter is defenitly some resistance. this one still has all the shippign oil on it but i had no trouble getting the tip to turn even with that. I would suspect the old center has worn the end of your mandrel sot hat the new center is not setting well enough. using tape as suggested will give the center more to bite on.
the fact your mandrel changed colors caught my eye as well. did it stay dark or blue. if so the temper is gone. this is nothing I have tried and actually tempering metal is much more involved than this. but you may be able to renew it by getting it hot again and then dropping a bit of motor oil on it. most tempering info I have read says the metal needs to be red hot. not sure you will need it hardened that much or if it ever was in the first place. If you where close enough I would just drill the end of your mandrel out for you. you may be able to find someone with a metal lathe that can do that.
not much more help than you have already gotten. I just hope the new day gives ou a fresh start, trust me I know just where you wher at.

 

[Mac In Oak Ridge]

You will find that the cone shape hole on the end of the mandrel doesn't come to a point. It has a drilled hole down at the bottom where the point goes.

For those familiar with metal lathes the hole in the end is made with a metal working center drill.

The first mandrel I bought didn't have the hole where the live center goes drilled deep enough. The point on the live center bottomed out before the cone shape surface touched. I chucked the mandrel up close to the headstock, it is the kind that has the Morse Taper with the clamping feature. I put drills in the hole till I got the one that was the same size as the recess and drilled it about 1/8 deeper.

 

[Carole in VA]

Originally posted by Mac In Oak Ridge
<br />You will find that the cone shape hole on the end of the mandrel doesn't come to a point. It has a drilled hole down at the bottom where the point goes.

For those familiar with metal lathes the hole in the end is made with a metal working center drill.

The first mandrel I bought didn't have the hole where the live center goes drilled deep enough. The point on the live center bottomed out before the cone shape surface touched. I chucked the mandrel up close to the headstock, it is the kind that has the Morse Taper with the clamping feature. I put drills in the hole till I got the one that was the same size as the recess and drilled it about 1/8 deeper.

That's an idea. I noticed from the wear on my original center that it looked like there was a hole in the bottom of the spindle. I tried the masking tape and no go. I don't think I have a drill small enough to drill the spindle hole down any deeper and since this is the only pen mandrel I have, I guess I am stuck with using the original center spur until after Christmas and I will just hope it continues to work. I don't think there is a problem with the new center as I compared it to a new center from Lee Valley and they are both about the same regarding freedom of movement. The good news is my Mom can come home from the hospital tomorrow if everything goes well, and I am frantically trying to get ready for a Christmas we were not sure we were going to have!
Merry Christmas everyone!!!![]