Long nose live center

[mksj]

My Skoda moves very freely, I would try to run it at speed with pressure for 1-2 hours and then repeat 2-3X and see if it improves. Maybe apply a little lube at the front seal. I use the extended point for the same reasons you mentioned. You can use a narrower insert/cutter to get closer to the the work end at the live center. Do not think a dead center will work very well, sounds like the material is fairly fragile.

 

[LeChuck]

It's hardy material but it cannot compare to metal of course. If I apply more pressure it will just enlarge the hole(until it starts bending), which means I'll have to trim more and waste material, and it can just make it fragile. But yeah, if there's resistance in the live center then the teeth of the steb center in the head will just dig a channel and rip it. Also have to be careful with heat. I'm going to try to reduce the speed to around 700rpm with a faster feed on those operations and see if it helps, as I'm also trying to get those resin chips to break (another issue I'm having). I'll try your recommendations. I did it for several minutes but didn't think to do it for an hour.

 

[Tozguy]

The preload on my new Shars seems fairly high, so some resistance. Is there anything wrong with the cheapy? Alternative, use a dead center and a little lube of some sort. Alternative #2: make yourself a spring loaded live center with the ideal nose design for your work and the perfect spring load.

#2. BINGO!
Thats what I did using a Weldon end mill holder and a broken end mill ground to a 60 deg. point.
Will dig out a photo if you are interested.

 

[LeChuck]

It would be interesting to see.

 

[Tozguy]

These are the components for making a live centre from a 3/8'' Weldon end mill holder.

The first version used a broken 1/8 TiN end mill that has a 60 deg. nose. A second version was made from a broken boring bar with a 3/8 shank (shown inserted in the end mill holder) because it had a longer nose.
The set screw in the holder is removed so that the hole can be used as an oil port. The ball bearings are 5/16''. Tension on the spring is adjustable using the 3/8nc set screw in the drawbar threads.
I have used this live centre for a few hours and can say it absolutely works great. Believe me you will be amazed at the results.
Because of the tight fit of the end mill in the holder the end mill shank might need to be buffed/polished for it to spin freely. Once that is accomplished, even a thin oil will stay in place for extended periods.

 

[projectnut]

I would try breaking in the center using a piece of steel or aluminum round stock. Grip the stock in a collet or 4 jaw chuck, face it, and drill an appropriate depth 60* center using a center drill. Then move the tailstock with the center installed into position and start the lathe. With the lathe up to speed advance the tailstock into the center just far enough to start the center turning. Let the center turn for 10-15 minutes touching it occasionally to be sure it isn't over heating.

After running the center for the above recommended time shut down the lathe and back off the tailstock. At this point the center should turn relatively easy with finger pressure only. Keep in mind MT 3 centers are generally capable of supporting between 390 lbs. and 970 lbs. depending on the style you purchased. The higher the load capacity the more resistance you should expect.

As mentioned this may be a case where the material intended to be turned isn't dense enough to be able to apply sufficient pressure to the center without damaging the material itself.

 

[LeChuck]

Thanks for the photo, that's interesting.

So, I ran it for 30 minutes at 1000rpm. I didn't have time to supervise it for a whole hour today. I used it on a brass mandrel that I made for my pen turning, with a 60 degree hole in the end, tight. It got hot to the touch. I can't say objectively that I feel any difference after this. I also added oil anywhere it sorta made sense. I believe it turns a bit more easily by hand when I push it in while turning but I would think that I apply at least as much pressure when turning the resin. There is already a good amount, but maybe not enough for this center. The cheap enter turns much more freely without absolutely no effort with the fingers. I can try again later on with a piece of resin that I don't mind breaking with more pressure.

But yeah, this is probably a matter of centers like this being higher rated and needing more pressure than I can use here. The MT2 centers I have on my wood lathe are all free spinning like the cheaper MT3 I've been using.

 

[Tozguy]

An MT3 live centre would be rather big for turning pens. What if you bought a reducer sleeve so you could use an MT2 or MT1 live centre?

Tormach Rotary Table Upgrade - MT-1 Live Center - SKU 34104

The MT-1 Taper Live Center is for Light Duty Lathe Work

tormach.com

 

[LeChuck]

Sure. Adding sleeves would probably make it slightly less accurate, but the important thing is that it has no play and an extended nose. I do use a sleeve already in order to use a steb center inside my ER40 chuck.

 

[Tozguy]

Why would a live centre be less accurate when using a sleeve?