PDA

View Full Version : half-live center? :)



Tony
07-31-2015, 09:24 AM
I just ran into an interesting problem this morning that I've never seen before.

Turning small OD, supported in the tailstock, I needed to install my (carbide tipped) half dead center to
gain clearance for my tooling.

The dead center started burning up my work. It'd never done that before. I've always used minimal pressure
and a dab of oil now and again while it runs.

Turns out, because i was using insert tooling, my RPMs were maxed out (1200 for my lathe).. and the speed
was just too much.

Switched to live center didn't give me enough clearance, so I had to mickey-mouse it, swing the toolpost
and make the cut in two steps.

I've got that weird feeling now like there's a tail stock accessory out there that I'm missing. :)

loose nut
07-31-2015, 10:23 AM
600 RPM's for a dead center is about the most you should run and obviously there isn't a half "live" center. There are some live centers that have a fairly small tip that may be what you want. To lube a dead center use an extreme pressure grease, there are some made for just that purpose but most should do the job. If you take HSM magazine there are some adverts for this.

TGTool
07-31-2015, 10:31 AM
Also bear in mind that you should recheck the tailstock pressure frequently in a situation like this. The metal removal process can pour enough heat into the workpiece to expand it lengthwise and apply way more pressure than you started with.

Normanv
07-31-2015, 11:02 AM
This is something that I have worried about but never suffered from. I have just bought a live centre because I felt that I needed one but up to now I have used a dead centre with motor oil as a lubricant and have never had a problem. I don't use carbide tooling, only HSS, maybe that is why it has never been a problem.

wierdscience
07-31-2015, 11:19 AM
A CNC type extended nose center is a good fix for this problem.

http://www.ebay.com/itm/NEW-MT2-CNC-PRECISION-LONG-SPINDLE-LIVE-CENTER-MORSE-TAPER-2-0-000197-270lbs-/230847888767?pt=LH_DefaultDomain_0&hash=item35bf9b3d7f

JCHannum
07-31-2015, 11:19 AM
While not common among lower priced suppliers, long point live centers are available when tool clearance is a problem. There are other styles available for other applications. Prices are not for the faint of heart however.

http://www.royalproducts.com/img/category/upload/Special_LC.pdf

Toolguy
07-31-2015, 11:25 AM
Look for a CNC type center with a smaller extended point. Also, check www.royalproducts.com. They have a live center that is only as big as the taper (#3MT in my case) with the extended small point AND a die spring so it stays tight without getting too tight. A little spendy, very awesome. It's called a spring type live center, the part number of mine is 10533 #3MT.

Edit to add: I was typing at the same time as JCHannum.

bborr01
07-31-2015, 11:28 AM
You should be using high pressure lube, not oil. High pressure lube is made for using on dead centers. I also think your rpm's might be a little high.

This is the lube that I use: http://www.ebay.com/itm/Dart-LUBE-CMD-Extreme-Pressure-Lubricant-/111479101571?hash=item19f4ac1883&vxp=mtr

Brian

TGTool
07-31-2015, 12:05 PM
While not common among lower priced suppliers, long point love centers are available when tool clearance is a problem.



Obviously a product for guys who REALLY like their work. :D I'm not even going to consider what a "long point love center" might be if ordered from an adult product purveyor.

JCHannum
07-31-2015, 12:08 PM
Obviously a product for guys who REALLY like their work. :D I'm not even going to consider what a "long point love center" might be if ordered from an adult product purveyor.

Whoopsie. Error noted and edited.

bighammer
07-31-2015, 03:34 PM
use STP for dead center lube,


cookie

Rich Carlstedt
07-31-2015, 04:12 PM
I have been using a Climax live center for years
They are a superb product and have many different live centers
Here is a link to what mine looks like. I have a MT #2 ( CLX-2MT)
http://www.readytool.com/pdf%20files/page17.pdf

No relation to the web site mentioned...
Rich