Turning between centers both barrels?

[pmpartain]

Firstly, I haven't tried turning between centers yet. I've only been reading about it a couple weeks now. I like the idea of dropping the mandrel, and can see how turning without it would be much more accurate. However, I like to see both barrels at the same time. I like to shape them together to see how they fit together. So has anyone made custom bushings to do this. Let's take a cigar pen for example. Leave a 1/2 inch shank on the bushing for the nib. This shank can go into a beall collet chuck or the like. Leave a nice long tight fitting rod to go inside the barrel. Make the center bushing the 2 step kind like you buy. Again, nice long rods to go in the tubes. For the clip end bushing just put a 60 degree dimple, or you could leave a shank for one of those live centers that takes the inserts. May be other options as well. Turning 2 at once may not be as accurate as one at a time, but I bet it's way more accurate than using a mandreal, and still pretty good.

 

[Firefyter-emt]

It could be done easy enough and I can't see why it would not work, but there is a chance that it may not stay as true.

I will tell you what, I will make one for a slimline and see how it works. I was thinking about a custom center bushing for a modified Slimline anyway so it would be a good test.

The nice thing is that the larger the pen, the stronger the bushing would be. My only thought is I wonder if the "weight" in the center will have a bearing on the blank as it spins. If you have say a 2.5" long bushing, you really add in some weight between the tubes. It might work better for slimlines than a larger pen.

I will post up how it works out.

 

[Firefyter-emt]

Ok, I gave it a try. I think that a longer centerbushing is needed as I could tell there was some deflection when turning. The blank turned straight though so we shall see when it's put togather how good it feels. I personaly think that I would go with just one blank between center with a larger bushing for the mod.

Here are some photos ... I think there is someone making custom bushings if you take a look, he should be able to make this for you easily. I am going to try to stay out of it myself, I just don't have the time to make them easily. []

Pay no mind to the fact that the blanks are backwards, I was not paying attention to that when I turned the pen dangit! [!]

 

[pmpartain]

Dang Lee! You don't mess around. There was only a couple hours between those posts and you made the bushings and a pen! I never thought about the balance issue. I suppose you would be spinning a fair amount of metal on larger pens. If the thing is true should be pretty balanced though. I may see if I can get some made. We are supposed to get a metal working lathe at work soon, so maybe I could try making a set myself. Thanks for trying it out.

 

[Rifleman1776]

As FF said, there was some deflection. The set-up looks weak to me. I believe if you really want to see both blanks take shape in front of you while turning, the standard method of using a mandrel is the way to go as it provides the strength you need. An adjustable mandrel can be a big help in reducing flex however.

 

[pmpartain]

I'm using the Beall chuck with a mandrel, and I get good results. For larger pens I think that this setup could be stronger. Instead of a 1/4 inch rod that can flex inside the tube, you would have the maximum thickness inside there that should be stiffer, but like was said, I'm not sure about being out of balance.

I wonder why the bushings that we buy and not made of hardened tool steel. That would hold up much better. It also wouldn't hut for the part that sticks inside the tube to stick in a lot farther. This would stiffen up the mandrel rod a lot. In fact, that wouldn't be any different than my original post really. It would be better in that the whole assembly would be held together with the 1/4 inch road and the whole thing would be stiffened up by the longer nosed bushings.

 

[Blind_Squirrel]

Originally posted by pmpartain
<br />I'm using the Beall chuck with a mandrel, and I get good results. For larger pens I think that this setup could be stronger. Instead of a 1/4 inch rod that can flex inside the tube, you would have the maximum thickness inside there that should be stiffer, but like was said, I'm not sure about being out of balance.

I wonder why the bushings that we buy and not made of hardened tool steel. That would hold up much better. It also wouldn't hut for the part that sticks inside the tube to stick in a lot farther. This would stiffen up the mandrel rod a lot. In fact, that wouldn't be any different than my original post really. It would be better in that the whole assembly would be held together with the 1/4 inch road and the whole thing would be stiffened up by the longer nosed bushings.

Do you make and use bushings/inserts for your pen mill? If so, keep it in the tube while turning. I have found this to really firm things up.

 

[ashaw]

Originally posted by pmpartain
<br />I wonder why the bushings that we buy and not made of hardened tool steel. That would hold up much better.

Because they make them out of softer material is not to destroy your tools. A harden steel would take the edge off a chisel real quick.

 

[Firefyter-emt]

FWIW, I did make mine a little shorter than I should of. The shaft inside the tube is only 10mm lone with a 5mm bushing step. I could make one with maybe a 25mm shaft on each end and it might hold up better, but I think it would be much like mandrel turning. For the extra effort and cost, just but a good mandrel from Joe and mandrel turn. For me I feel that the blanks come out much better when turned BCB then with a mandrel.

Feel free to test it further, you might like it. You will still achieve the fast blank removal from the lathe and the dead center is perfect for CA application. (one blank at a time)

 

[pmpartain]

I do make the sleeves for the pen mill, and that sounds like a great idea. I've made my adapters out of delrin and wood on a 7mm tube. Maybe the plastic wouldn't add much as far as rigidity goes, but the wood and tube would. Again, I don't see much benefit to this for 7mm kits, but for kits with larger tubes, I could see an advantage maybe. Sounds like I'll be doing some metal lathe work when I get the chance. Can't hurt to give it a shot right?