TBC live center?

[Woodchipper]

Received the TBC setup a while back and like it. However, I have noticed the live center gets hot after a few minutes of turning. I hesitate to run it for a long time to turn down a blank. Working on a synthetic (not sure what it is) right now. Taking my time as I have been out of the shop for a while and working slowly. Is heating of the live center normal?

 

[SabertoothBunny]

No, that is not normal for TBC bushings. I use them for single blank projects fairly regularly and have never had the bushings overheat.

There is something cause excess friction to occur that is generating that heat. This implies that the centers may not be centered all the way which causing them to push int alignment from the bushing creating the friction. I would start with verifying your centers are true and if they are, reach out to TBS directly to see if they have any recommendations.

 

[leehljp]

1. Is it your bushings or your live center itself that is hot, or both?

2. How easy or hard is it to turn the live center with your hand?

3. Do you feel any resistance when turning the live center by hand?

4. If no resistance when turning the LC by hand, is it possible that you may be pulling the tail stock up a little too tight?

5. Lastly, what specific live center are you using?

 

[egnald]

Are you referring to the PSI Turn Between Centers setup? Most live centers will run warm which is generally OK. Although bearings reduce friction, they don't eliminate it, and friction = heat. So warm should be OK, but Hot is usually an indication of a problem. Since most live centers do not incorporate thrust bearings, excessive heating is often due to excessive side load caused by overtightening the tailstock. (This is bad for the drive bearings in the lathe's headstock too!)

Regards,
Dave

 

[Woodchipper]

Live center is heating up, not the bushings.
Lee, it's the TBC mandrel set from Exotic Blanks/PSI.
Dave, thanks for the reminders. Will be conscious of the bearings. I like to snug the tail stock down so the blank doesn't spin but not too much stress on the bearings.
So...back to the shop!

 

[KenB259]

Live center is heating up, not the bushings.
Lee, it's the TBC mandrel set from Exotic Blanks/PSI.
Dave, thanks for the reminders. Will be conscious of the bearings. I like to snug the tail stock down so the blank doesn't spin but not too much stress on the bearings.
So...back to the shop!

For what it's worth. I use the same setup, mine doesn't get warm at all.

 

[Woodchipper]

I finished turning two blanks for a pen. I was careful to crank the quill down to where the blank on the TBC mandrel would barely turn with a bit of light pressure. Cranked it a smidgen more. Finished turning the two pieces and the mandrel was barely warm to the touch. Problem solved with a big thank you to the members here.

 

[jrista]

I finished turning two blanks for a pen. I was careful to crank the quill down to where the blank on the TBC mandrel would barely turn with a bit of light pressure. Cranked it a smidgen more. Finished turning the two pieces and the mandrel was barely warm to the touch. Problem solved with a big thank you to the members here.

I'm a bit late, but over-cranking the tightness of the live center was probably the problem. In addition to the heating problem, over-cranking can also cause problems with roundness, in my experience, due to changes in the seating of the bearing and thus the angle of that "pin" on the live center. I do tighten mine to reasonably snug, which is probably tighter than "just barely gets the blank spinning", because I find that I get too much slippage if I just barely tighten. I don't use this (I have the PSI TBC centers) too often these days (only for finishing, no longer for turning, as I've cone to pure TBC with TBC bushings instead, which I find gives me superior roundness and fit to the fittings), but when I was primarily using this, I do not recall the live center ever getting hot, or even warm. I tend to turn at around 3000-3600 RPM, so there was quite a bit of speed and thus friction.

I do wonder, if your live center is getting hot to the touch, if the bearing is packed properly. There is an appropriate level of grease (and it must be a good grease, NOT an oil) in the bearing. If there is not, then that might lead to undue heating. If possible, you might try and see if the bearing IS packed with the proper amount of grease. I generally prefer a synthetic grease for bearings these days (picked up a tub of it years and years ago...and boy, its STILL going strong...so much grease! It wasn't that large of a tub, but its been sufficient for a countless number of bearings at this point and is still mostly full. )

 

[Woodchipper]

jrista, are you suggesting to disassemble the live center to check for grease?

 

[Smokey S]

I have had the same set up for about a year or so, and never felt any heat on the live center. Just saying……Smokey

 

[jrista]

jrista, are you suggesting to disassemble the live center to check for grease?

I don't know if there is an easy way to check. If you would have to completely disassemble it, then I would NOT do that...

 

[Woodchipper]

Like disassembling an old typewriter: Easy but impossible to reassemble. AMHIK
To all: I played around with the quill tension. Turned it down to where the blank had a bit of resistance to spinning. Then I tightened it a whisker and turned the blank a few minutes. Slightly warm but not like before.

 

[pacer_3iii]

Mine has a cover over the back that comes off pretty easily. In fact, the first one I bought was MT1 and it came off on its own while turning all the time and I had to put blue loctite on it just to get it to stay on. The newer MT2 one doesn't do this, but I'm confident I can still get the back off if I need to.

 

[Woodchipper]

pacer_3iii, I'll take a look at the live center just for funsies.

 

[Jans husband]

I have had the same set up for about a year or so, and never felt any heat on the live center. Just saying……Smokey

Sorry--cant resist!!
Why are you called Smokey then??
seriously, I don't have problems with TBC heat. I prefer TBC to mandrel turning,

Mike

 

[wouldentu2?]

If there is away to let a couple drops of oil seep in try that a see if it gets better

 

[jrista]

If there is away to let a couple drops of oil seep in try that a see if it gets better

I would be wary of oil in bearings. It may provide some initial benefit, but it will leak out, faster with higher RPM, and then you'll have friction issues again. It is better to use a good quality grease.

 

[jrista]

So I took a look at my PSI #PKMBCM2 TBC mandrel, which I purchased, probably close to three years ago now. This model has a metal plate on the back of the live center with two holes in it. You would need some kind of spanner wrench to unscrew it, but it looks like it is possible to pull this plate off, which should give you access to the bearings. What I would do, is mark the plate and the body of the center with lines crossing over both (say with a marker), so that when you finish greasing, you can restore the plate to its original orientation and depth (don't want too much, or too little, tension on the bearing from the plate, usually.) Then remove the plate, grease the bearing if it needs it, and restore the plate.

I've seen another version of a TBC mandrel, maybe it was a different morse taper, that I thought had one of those black plastic covers that you can usually just pop off. If you have that, then you should be able to just pull that cover off, grease the bearing, and restore the cover.

With my particular TBC mandrel, the bearing is just tight enough to have no play, which IMO is optimal. No play means that you don't have to tighten too much to take out any slop (sometimes I find that my standard 60 degree live centers have a bit of slop, and you need to tighten more to take that up.) If you have some slop, you might want to try and adjust the cover plate tighter, just to the point where you can no longer wiggle the bearing back and forth by hand. THEN mark that orientation, then remove the plate and grease.