out of round brass tubes, a bad thing?

[Dan_F]

I have to make a couple of Ligero roller balls, and it seems that all of my tubes are somewhat out of round. I typically sand the tubes on the lathe before gluing, and there is a noticeable bumpy sensation when touching the tubes as they turn.

The question is, will this make any difference once they are glued into the blank? I'm thinking maybe so, since the tube is the point of reference. I turn between centers, and only use the bushing for roughing out, doing the final shaping without bushings. So if the tube is off, it would seem that the barrel would be thrown off too. What do you think?

Dan

 

[Skye]

I would think that it would put the turning out of round. I don't know for sure, but I know my time is to scarce to waste it turning something that may be doomed from the start.

 

[KenV]

My experince with machining suggests that it will work until you put a concentric solid Nib etc into an oval opening and distort it. If your centering process pulls the brass into a "round" while turning and it matches the fittings, all is well. Otherwise you will have missed matches or cracks. The key is the amount - a few thousands are not likely to be an issue. The larger the deviation, the greater the challenge/risk/opportinity.

It is one of those "may you live in interesting times" balance points. I am cheap and tend to try these sorts of things.

 

[jskeen]

Get the best of both worlds, Order some new tubes and turn your pens, but keep the OOR ones and some time when you're bored, throw a junk blank on them and turn it to see if it works.

Then post and let us know, of course!

 

[sbell111]

You could just throw a junk blank on them and see what happens. If it works, turn off the blank and reuse the tube for a good blank, if not, complain to CSUSA and ask them to send you good tubes.

 

[Randy_]

Dan: Did you put a caliper on the tubes and measure the variance? Are the tubes so far out of round that the bushings will not slip into the tubes without some effort?​

Remember that the holes drilled in the blanks are a little over-sized and the gap will be filled with glue so a small variance may not be a problem. When you turn the blank, you should get a round blank, regardless; but I see two potential problems. Firstly, if the end of each tube is slightly less than round, you may have difficulty pressing the hardware into the tubes and if the hardware does go in, it may create some stresses in the tube and surrounding wood that may crack the wood.

Other problem is that the hardware may not "center" in the tube exactly the same as did the bushing so even though the blank is perfectly round, it still might not quite match up with the hardware.

You might see if you can "adjust" the tubes a little by squeezing them with a pair of pliers; but the sensible thing to do is just get another set of tubes.....unless there is some sort of time deadline involved and you can't wait.

Note: I just went back and reread your post and discovered I missed the fact that you were turning between centers. That being the case, I pretty much agree with Ken's thinking. You might be able to get away with it; but the better choice would to get new tubes.​

 

[Dan_F]

Thanks guys. I went through all of my Ligero/El Grande tubes - spares and kits, and found 11 bad ones, which were off by about 3-4 thousandths. Most were the larger tubes, on had two bad of the smaller. I do have enough good ones to get started on the pens I need to do right away. CSUSA has been very good about customer service issues, and I'm sure they will replace these. If I ever get bored, I may try loading up one of the bad ones just to see what happens, but I just don't see much good coming of it.

Dan

 

[nava1uni]

Did you notice the bumps before you began sanding the tubes. If not then maybe you are putting too much pressure on them when sanding?

 

[Dan_F]

Did you notice the bumps before you began sanding the tubes. If not then maybe you are putting too much pressure on them when sanding?

Nope, they were like that to start with.

Dan