Originally posted by wizical
<br />the live center is wearing down at the tip when it is inserted into the mandrel. I cant figure out why
Keven,
This set of countersinks will give you what you need to redrill the end of the mandrel:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42280
If you look at the large countersink, you will see how there is additional depth to the tip of the bit to allow the live center's tip to seat on the 60 degree side and not bottom out.
Before 'live centers' in metal work, the center was non-revolving. The lathe operator would apply a lead paste in the hole and bring up the center. Pressure was 'lightly' applied so as to retain some lead and squeeze out the excess. One developed a touch for the amount of friction/pressure while constantly checking the tailstock to prevent damage.
Remember, heat will also build up on the center and mandrel as it revolves and also heat from your cutting tool. This causes the mandrel to expand and give you the famous 'out-of-round' condition. Additionally, I suspect that many turners that complain of tail stock alignment are really bottoming the center's tip in the mandrel and causing a wobble or out of round condition especially as things heat up.
I also find that HF has a fairly inexpensive live center:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=38573
I personally drill the end of my mandrels with a countersink (who knows what was used in China) and use a metal lathe MT2 live center in my tailstock. Still I check it while turning to see if too loose or too tight.
YMMV...Jim