TBC questions

[Woodchipper]

I have a 60 degree live center for the tailstock and a 60 degree dead center for the headstock. So far, so good in turning a couple of blanks. I noticed some brass dust on the centers after turning. I'm thinking that the blank was slipping a bit. I don't want to tighten the quill too much to expand the tube. I'm not using TBC bushings- is this necessary? I have watched some videos where bushings were used and some that didn't use them. Your help is most appreciated. BTW, calipers are getting a good workout with TBC!

 

[turncrazy43]

Try the PSI turn between centers jig. About $30. They allow you to use standard bushings. Includes a dead center and live center.
Turncrazy43

 

[Woodchipper]

Already have the DC and LC so that would be duplicating what I have. Will take a look at it, though. Might be a good Christmas present for the wife.
Edit-is this what you mention? If so, I'm trying to get away from bushings altogether. I have some kits that require bushings that I don't have.
https://www.pennstateind.com/store/PKMBCM2.html

 

[Curly]

That is the essence of turning between centres. You keep just enough pressure to turn the blank on the cones. It does mean of course you need to be able to cut with very light cutting forces and not brute your way through. I don't use scraping methods, preferring the skew or a gouge. When you have the touch you will have a very light chamfer but not flared end and there may be a little brass on the centre. You can use normal bushings directly on the cone centres to get most of the rounding and rough turning done and then remove them to finish in just the centres. That way the poorer quality mandrel bushing out of roundness won't affect the finished product.

 

[Woodchipper]

Thanks, Curly. Good info. I have plenty of bushings to rough the blank, remove the bushings and turn to dimensions. I'll practice with a skew for a light cut; I use a 3/4" roughing gouge to turn the blank, wood or synthetic.

 

[JoeCallahan]

A good way to add a little more grip to your centers is to apply some beeswax to them. I lightly scuffed the surfaces of my dead and live centers with some 600 grit paper, just to give the beeswax something to grab. It's not much, but I've had much fewer problems with slipping ever since. I like to apply a little more wax every few months or so.

 

[Woodchipper]

Thanks, Joe.

 

[1shootist]

A good way to add a little more grip to your centers is to apply some beeswax to them. I lightly scuffed the surfaces of my dead and live centers with some 600 grit paper, just to give the beeswax something to grab. It's not much, but I've had much fewer problems with slipping ever since. I like to apply a little more wax every few months or so.

Good info...i'm going to give it a try.
I get more slippage than I'm comfortable with..
I already made the mistake of flaring out the brass ends to the point I needed to CA the first pieces in.

 

[leehljp]

While not everyone does this, slippage is prevented by using the bushings while turning down to size or close to size, then taking the bushings off for final sizing and finishing. That bushing to no bushing process only takes about 5 to 7 seconds.

There are some who do not use bushings at all to get started; I can't do it that way without slippage, and I'm the one that started that craze here.

 

[Woodchipper]

I would still need bushings to fit the tube for initial turning. There might be bushings that would fit the tube, even though I wouldn't need them for the final dimensions. Will check on this as I have several bushings already. Thanks, Hank.

 

[magpens]

As the driving dead center in the headstock, I use a diamond coated cone to give a better grip on the brass tube end.

These diamond cones are designed for sharpening square chisels, or square hole punches.

I buy my cones from Lee Valley, but there are other sources. . Here is a link so you can see what am referring to:

Cone Sharpeners for Square Hole Punches - Lee Valley Tools

www.leevalley.com

 

[More4dan]

It does help to turn round between centers before drilling and gluing in the tube. If I'm using a cast blank with the tube in it, I will sand off the corners before turning.


Sent from my iPhone using Penturners.org mobile app

 

[seaclanky]

Hi Woodchipper. I like to TBC so that I can get the concentricity required. This is fine when I'm using 7mm tubes, however i find that the 10mm tubes don't sit well on my four-prong dead centre. Then I found that switching to my mini chuck and holding a scrap dowel, a jam chuck can be very easily turned. The advantage of this is that it will be dead concentric and if you make it with a fairly shallow taper you'll find that it provides adequate drive. I imagine that this would work OK with 7mm tubes also.

i agree with More4dan, it helps to turn round between centres before mounting in the chuck for drilling. When using segmented blanks I find that if I use the meeting point of the segments as the desired centre and then carefully centre-pop this, then the blank can be fitted between 60 deg centres and turned cylindrical and concentric.

Hope this helps.

 

[Curly]

Seaclanky I've never heard of anyone using the four prong dead center to turn a pen between centres. All I've ever heard of and used is a sixty degree dead center. Your making a dead centre of sorts in a chuck is used occasionally by some but they usually don't have a Morse taper in their headstock. Each to their own of course.

 

[leehljp]

Seaclanky I've never heard of anyone using the four prong dead center to turn a pen between centres. All I've ever heard of and used is a sixty degree dead center. Your making a dead centre of sorts in a chuck is used occasionally by some but they usually don't have a Morse taper in their headstock. Each to their own of course.

60° are needed for mandrel ends, or for bushings made specifically for 60° centers, but for normal bushings with normal holes or tubes only, the dead center degree doesn't really matter.
The first drive center posted on this forum:

Imported Photo from leehljp

Imported Photo from leehljp. Please edit title and description.

www.penturners.org

 

[Curly]

I understand the cone angle doesn't matter but a prong centre is okay to you for TBC of a tubed blank??? I see some danger in it. I have no problem sitting corrected if others are doing it regularly but I won't.

 

[leehljp]

I understand the cone angle doesn't matter but a prong centre is okay to you for TBC of a tubed blank??? I see some danger in it. I have no problem sitting corrected if others are doing it regularly but I won't.

I used the cone center in the tube AFTER it (the blank) was turned round and down to near size.